DetNet J. Korhonen, Ed.
Internet-Draft Broadcom
Intended status: Informational J. Farkas
Expires: September 22, 2016 G. Mirsky
P. Thubert
Y. Zhuang
L. Berger
March 21, 2016

DetNet Data Plane Protocol and Solution Alternatives


This document identifies existing IP and MPLS, and other encapsulations that run over IP and/or MPLS data plane technologies that can be considered as the base line solution for deterministic networking data plane definition.

Status of This Memo

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Table of Contents

1. Introduction

Deterministic Networking (DetNet) [I-D.finn-detnet-problem-statement] provides a capability to carry unicast or multicast data flows for real-time applications with extremely low data loss rates and known upper bound maximum latency [I-D.finn-detnet-architecture]. The deterministic networking Quality of Service (QoS) is expressed as 1) the maximum end-to-end latency from sender (talker) to receiver (listener), and 2) probability of loss of a packet. Only the worst-case values for the mentioned parameters are concerned.

There are three techniques to achieve the QoS required by deterministic networks: [RFC3031], layer-2 or layer-3 encapsulations and transport protocols that could be considered as foundations for a deterministic networking data plane. The full scope of the deterministic networking data plane solution is considered including, as appropriate: quality of service (QoS); Operations, Administration and Maintenance (OAM); and time synchronization among other criteria described in Section 3.

This document identifies existing IP and Multiprotocol Label Switching (MPLS)

This document does not select a deterministic networking data plane protocol. It does, however, elaborate what it would require to adapt and use a specific protocol as the deterministic networking data plane solution. This document is only concerned with data plane considerations and, specifically, with topics that potentially impact potential deterministic networking aware data plane hardware. Control plane considerations are out of scope of this document.

2. DetNet Data Plane Overview

[Editor's note: all/portions of the following may be moved to the DetNet Architecture document at some future point.]

A "Deterministic Network" will be composed of DetNet enabled "End Systems", DetNet enabled "Edge Nodes", and DetNet enabled "Network Nodes". DetNet enabled nodes will provide a DetNet service to attached DetNet End Systems. All DetNet enabled systems and nodes will be interconnected by sub-networks. These sub-networks will provide DetNet compatible service for support of DetNet traffic. Examples of sub-networks include 802.1TSN and a point-to-point OTN link. Of course, multi-layer DetNet systems may be possible too, where one DetNet appears as a sub-network, and provides service to, a higher layer DetNet system. A simple DetNet is shown in Figure 1.

+------+                                                +------+
| End  |<-------------Deterministic flow--------------->| End  |
|System|                                                |System|
+--+---+                                                +-+----+
   |      <--------------DetNet flow----------------->    |
   |                                                  ,+-''''--.
   |                                                  [   Sub   ]
   |Link                                              [ Network ]
   |                                                   +-....--'
   |                                                      |
   |    +------+     +-------+   ,-'''-.   +-------+  +------+
   |    | Edge |Link |Network|--[  Sub  ]--|Network|--| Edge |
   +----| Node |-----|  Node |  [Network]  |  Node |  | Node |
        +------+     +-------+   +-...-'   +-------+  +------+

Figure 1: A Simple DetNet Enabled Network

This DetNet data plane is logically divided into two layers:

Distinguishing the function of these two DetNet data plane layers helps to explore and evaluate various combinations of the data plane solutions available. This separation of DetNet layers, while helpful, should not be considered as formal requirement. For example, some technologies may violate these strict layers and still be able to deliver a DetNet service.

A number of data plane technology candidates are discussed later in this document. They can be mapped to the two layers as shown in Figure 2.

|  Service  | PW, RTP, UDP, GRE, L2TP, VXLAN
| Transport | IPv6, IPv4, MPLS LSPs, BIER, BIER-TE

Figure 2: DetNet adaptation to data plane

Both the DetNet Service and the DetNet Transport layers are provided by a single technology in some solutions, e.g. the DetNet Service layer is PW and the DetNet Transport layer is MPLS in case of PW over MPLS. Nonetheless, both the DetNet Service and the DetNet Transport layers can include multiple technology layers in other solutions in order to provide the capabilities needed for DetNet flows. For instance, the DetNet Transport layer can comprise MPLS-in-GRE (Section 4.2.5) in one solution. In another solution, the DetNet Service layer can include, e.g., RTP in UDP (Section 4.2.8).

[Editor's note: I'm not sure if the remainder of this section says anything not present in the next section. Will need to revisit as part of the pre-pub review.]

There are many valid options to create a data plane solution for DetNet traffic by selecting a technology approach for the DetNet Service layer and also selecting a technology approach for the DetNet Transport layer. There are a high number of valid combinations. Therefore, not the combinations but the different technologies are evaluated along the criteria collected in Section 3. Different criteria apply for the DetNet Service layer and the DetNet Transport layer, however, some of the criteria are valid for both layers.

The criteria for the DetNet Service layer:

  • #1 Encapsulation and overhead
  • #2 Flow identification (Flow ID part of the DetNet flows)
  • #3 Packet sequencing (sequence number)
  • #5 Packet replication and deletion (note: only the packet deletion for seamless redundancy)
  • #6 Operations, Administration and Maintenance (capabilities)
  • #7 Time synchronization (e.g., time stamping)
  • #8 Class and quality of service capabilities (DetNet Service specific)
  • #10 Technical maturity

The criteria for the DetNet Transport layer:

  • #1 Encapsulation and overhead
  • #2 Flow identification
  • #4 Explicit routes (network path)
  • #5 Packet replication and deletion (note: only the packet replication for seamless redundancy)
  • #6 Operations, Administration and Maintenance (capabilities)
  • #7 Time synchronization (time/phase sync of nodes)
  • #8 Class and quality of service capabilities (DetNet Transport specific)
  • #9 Packet traceability (verification purposes)
  • #10 Technical maturity

  • [Editor's note: #7 is more of OAM feature.]

Some of the criteria are relevant for both the DetNet Service and DetNet Transport layers. The two layers provide together what is needed to meet certain criteria, e.g., flow identification. Different aspects are valid for the two different layers for other criteria, e.g., time synchronization. Furthermore, technical maturity is a criteria valid for both layers.

3. Criteria for data plane solution alternatives

This section provides criteria to help to evaluate potential options. The criteria can be broken down based on layer. That is if the criteria is focused on delivering DetNet service adaptation, i.e., is concerned with the DetNet Service layer, or if the criteria is focused on transporting flows across an end to end DetNet domain. [Editor's note: which is TBD.]

Each deterministic networking data plane solution alternative is described and evaluated using the criteria described in this section. The used criteria enumerated in this section are selected so that they highlight the existence or lack of features that are expected or seen important to a solution alternative for the data plane solution.

3.1. #? DetNet Service Interface

[Editor's note: this criteria needs a bit more discussion.]

One of the most fundamental differences between different potential data plane options is the basic addressing and headers used by DetNet clients. For example, is the basic service a Layer 2 (e.g., Ethernet) or Layer 3 (i.e., IP) service. This decision impacts how DetNet end points are addressed, and the basic forwarding logic of the DetNet Service layer.

3.2. #1 Encapsulation and overhead

Encapsulation and overhead is related to how the DetNet data plane carries DetNet user traffic. In several cases a deterministic flow has to be encapsulated inside other protocols, for example, when transporting a layer-2 Ethernet frame over an IP transport network. In some cases a former tunneling like encapsulation can be avoided by underlying transport protocol translation, for example, translating layer-2 Ethernet frame including addressing and flow identification into native IP traffic. Last it is possible that talkers and listeners handle deterministic flows natively in layer-3. This criteria concerns what is the encapsulation method the solution alternative support: tunneling like encapsulation, protocol translation or native layer-3 transport. In addition to the encapsulation mechanism this criteria is also concerned of the processing and specifically the encapsulate header overhead.

3.3. #2 Flow identification

The solution alternative has to provide means to identify specific deterministic flows. The flow identification can, for example, be explicit field in the data plane encapsulation header or implicitly encoded into the addressing scheme of the used data plane protocol or their combination. This criteria concerns the availability and details of deterministic flow identification the data plane protocol alternative has.

3.4. #3 Packet sequencing

[Editor's note: is in order delivery a strict requirement? if so, it should be stated as such and separately from any other requirement. There are multiple ways to solve this criteria.]

The solution alternative has to provide means for end systems to number packets sequentially and transport that sequencing information along with the sent packets. In addition to possible reordering packets one of the important uses for sequencing is detecting duplicates. In a case of intentional packet duplication a combination of flow identification and packet sequencing allows for detecting and discarding duplicates at the receiver (see Section 3.6 for more details). This criteria concerns the availability and details of the packet sequencing capabilities the data plane protocol alternative has.

3.5. #4 Explicit routes

The solution alternative has to provide a mechanism(s) for establishing explicit routes that all packets belonging to a deterministic flow will follow. The explicit route can be seen as a form of source routing or a pre-reserved path e.g., using some network management procedure. It should be noted that the explicit route does not need to be detailed to a level where every possible intermediate node along the path is part of the named explicit route. RSVP-TE [RFC3209] supports explicit routes, and typically provides pinned data paths for established LSPs. At Layer-2, the IEEE 802.1Qca [IEEE8021Qca] specification defines how to do explicit path control in a bridged network and its IETF counter part is defined in [I-D.ietf-isis-pcr]. This criteria concerns the available mechanisms for explicit routes for the data plane protocol alternative.

3.6. #5 Packet replication and deletion

The objective for supporting packet replication and deletion is to enable hitless (or lossless) 1+1 protection, which is also called Seamless redundancy in [I-D.finn-detnet-architecture]. Data plane solutions need to meet this objective independent of the particular solution used. In other words, a packet replication and deletion is one identified method for a data plane solution to provide seamless redundancy and other methods, if so identified, are permissible.

The solution alternative has to provide means for end systems and/or relay systems to be able to replicate packets, and later eliminate all but one of the replicas, at multiple points in the network in order to ensure that one (or more) equipment failure event(s) still leave at least one path intact for a deterministic networking flow. The goal is to enable hitless 1+1 protection in a way that no packet gets lost or there is no ramp up time when either one of the paths fails for one reason or another.

Another concern regarding packet replication is how to enforce replicated packets to take different route while the final destination still remains the same. With strict source routing, all the intermediate hops are listed and paths can be guaranteed to be non-overlapping. Loose source routing only signals some of the intermediate hops and it takes additional knowledge to ensure that there is no single point of failure.

[Editor's note: at the DetNet Transport layer this criteria does not concern packet deletion, only the packet replication. The packet deletion belongs to the DetNet Service layer]

The IEEE 802.1CB [IEEE8021CB] is an example of Ethernet-based solution that defines packet sequence numbering, packet replication, and duplicate packet identification and deletion. The deterministic networking data plane solution alternative at layer-3 has to provide equivalent functionality. This criteria concerns the available mechanisms for packet replication and duplicate deletion the data plane protocol alternative has.

3.7. #6 Operations, Administration and Maintenance

The solution alternative should demonstrate an availability of appropriate standardized OAM tools that can be extended for deterministic networking purposes with a reasonable effort, when required. The OAM tools do not necessarily need to be specific to the data plane protocol as it could be the case, for example, with MPLS-based data planes. But any OAM-related implications or requirements on data plane hardware must be considered.

3.8. #7 Time synchronization

Time synchronization between DetNet systems and nodes can be used to enable fine grain scheduling of traffic along an end-to-end data path. Such scheduling can be used to deliver very low jitter and latency. [DetNet-ARCH] refers to a synchronization target of less than 1 microsecond. Meeting such time synchronization objectives is likely to require specific hardware support, both at the synchronization protocol level and at the (time synchronized) packet scheduling level. It is worth noting that certain aspects of time synchronization and packet scheduling may be provided by the underlying sub-net technology, e.g., [IEEE802.1Qbv] and [IEEE802.1Qch].

3.9. #8 Class and quality of service capabilities

Class and quality of service, i.e., CoS and QoS, are terms that are often used interchangeably and confused. In the context of DetNet, CoS is used to refer to mechanisms that provide traffic forwarding treatment based on aggregate group basis and QoS is used to refer to mechanisms that provide traffic forwarding treatment based on a specific DetNet flow basis. Examples of CoS mechanisms include DiffServ which is enabled by IP header differentiated services code point (DSCP) field [RFC2474] and MPLS label traffic class field [RFC5462], and at Layer-2, by IEEE 802.1p priority code point (PCP).

Quality of Service (QoS) mechanisms for flow specific traffic treatment typically includes a guarantee/agreement for the service, and allocation of resources to support the service. Example QoS mechanisms include discrete resource allocation, admission control, flow identification and isolation, and sometimes path control, traffic protection, shaping, policing and remarking. Example protocols that support QoS control include Resource ReSerVation Protocol [RFC2205] (RSVP) and RSVP-TE [RFC3209] and [RFC3473].

A critical DetNet service enabled by QoS (and perhaps CoS) is delivering zero congestion loss. There are different mechanisms that maybe used separately or in combination to deliver a zero congestion loss service. The key aspect of this objective is that DetNet packets are not discarded due to congestion at any point in a DetNet aware network.

In the context of the data plane solution there should be means for flow identification, which then can be used to map a flow against specific resources and treatment in a node enforcing the QoS. Hereto, certain aspects of CoS and QoS may be provided by the underlying sub-net technology, e.g., actual queuing or IEEE 802.3x priority flow control (PFC).

3.10. #9 Packet traceability

For the network management and specifically for tracing implementation or network configuration errors any means to find out whether a packet is a replica, which node performed replication, and which path was intended for the replica, can be very useful. This criteria concerns the availability of solutions for tracing packets in the context of data plane protocol alternative. Packet trace is a form of OAM.

3.11. #10 Technical maturity

The technical maturity of the data plane solution alternative is crucial, since it basically defines the effort, time line and risks involved for the use of the solution in deployments. For example, the maturity level can be categorized as available immediately, available with small extensions, available with repurposing/redefining portions of the protocol or its header fields. Yet another important measure for maturity is the deployment experience. This criteria concerns the maturity of the data plane protocol alternative as the solution alternative. This criteria is particularly important given, as previously noted, that the DetNet data plane solution is expected to impact, i.e., be supported in, hardware.

4. Data plane solution alternatives

The following sections describe and rate deterministic data plane solution alternatives. In "Analysis and Discussion" section each alternative is evaluated against the criteria given in Section 3 and rated using the following: (M)eets the criteria, (W)ork needed, and (N)ot suitable or too much work envisioned.

4.1. DetNet Transport layer technologies

4.1.1. Native IPv6 transport Solution description

This section investigates the application of native IPv6 [RFC2460] as the data plane for deterministic networking along the criteria collected in Section 3.

The application of higher OSI layer headers, i.e., headers deeper in the packet, can be considered. Two aspects have to be taken into account for such solutions. (i) Those header fields can be encrypted. (ii) Those header fields are deeper in the packet, therefore, routers have to apply deep packet inspection. See further details in Section 4.2.8. Analysis and Discussion

Encapsulation and overhead (M/W)

The DetNet Service layer encapsulated DetNet flows are assumed to be handled natively at layer-3 by IPv6 at the first place. The fixed header of an IPv6 packet is 40 bytes [RFC2460]. This overhead is bigger if any Extension Header is used, and a generic behaviour for host and forwarding nodes is specified in [RFC7045]. However, the exact overhead (Section 3.2) depends on what solution is actually used to provide DetNet features, e.g., explicit routing or seamless redundancy if any of these is applied.

IPv6 has two types of Extension Headers that are processed by intermediate routers between the source and the final destination and may be of interest for the data plane signaling, the Routing Header that is used to direct the traffic via intermediate routers in a strict or loose source routing way, and the Hop-by-Hop Options Header that carries optional information that must be examined by every node along a packet's delivery path. The Hop-by-Hop Options Header, when present, must immediately follow the IPv6 Header and it is not possible to limit its processing to the end points of Source Routed segments.

IPv6 also provides a Destination Options Header that is used to carry optional information to be examined only by a packet's destination node(s). The encoding of the options used in the Hop-by-Hop and in the Destination Options Header indicates the expected behavior when a processing IPv6 node does not recognize the Option Type, e.g. skip or drop; it should be noted that due to performance restrictions nodes may ignore the Hop-by-Hop Option Header, drop packets containing a Hop-by-Hop Option Header, or assign packets containing a Hop-by-Hop Option Header to a slow processing path [I-D.ietf-6man-rfc2460bis] (e.g. punt packets from hardware to software forwarding which is highly detrimental to the performance).

The creation of new Extension Headers that would need to be processed by intermediate nodes is strongly discouraged. In particular, new Extension Header(s) having hop-by-hop behavior must not be created or specified. New options for the existing Hop-by-Hop Header should not be created or specified unless no alternative solution is feasible [RFC6564].

Flow identification (M/W)

The 20-bit flow label field of the fixed IPv6 header is suitable to distinguish different deterministic flows. But guidance on the use of the flow label provided by [RFC6437] places restrictions on how the flow label can be used. In particular, labels should be chosen from an approximation to a discrete uniform distribution. Additionally, existing implementations generally do not open APIs to control the flow label from the upper layers.

Alternatively, the Flow identification could be transported in a new option in the Hop-by-Hop Options Header.

Explicit routes (W)

The general assumption is that a Software-Defined Networking (SDN) [RFC7426] based approach is applied to compute, establish and manage the explicit routes, leveraging Traffic Engineering (TE) extensions to routing protocols [RFC5305] [I-D.ietf-idr-ls-distribution] and evolving to the Path Computation Element (PCE) Architecture [RFC5440], though a number of issues remain to be solved [RFC7399].

Segment Routing (SR) [I-D.ietf-spring-segment-routing] is a new initiative to equip IPv6 with explicit routing capabilities. The idea for the DetNet data plane would be to apply SR to IPv6 with the addition of a new type of routing extension header [I-D.ietf-6man-segment-routing-header] to explicitly signal the path in the data plane between the source and the destination, and/or between replication points and elimination points if this functionality is used.

Another concern regarding packet replication is how to enforce replicated packets to take different route while the final destination still remains the same. With strict source routing, all the intermediate hops are listed and paths can be guaranteed to be non-overlapping. Loose source routing only signals some of the intermediate hops and it takes additional knowledge to ensure that there is no single point of failure.

Packet replication (W)
The functionality of replicating a packet exists in IPv6 but is limited to multicast flows.

In order to enforce replicated packets to take different routes, IP-in-IP encapsulation and Segment Routing could be leveraged to signal a segment in a packet. A replication point would insert a different routing header in each copy it makes, the routing header providing explicitly the hops to the elimination point for that particular replica of the packet, in a strict or in a loose source routing fashion. An elimination point would pop the routing headers from the various copies it gets and forward or receive the packet if it is the final destination.

Operations, Administration and Maintenance (M/W)

IPv6 enjoys the existing toolbox for generic IP network management. However, IPv6 specific management features are still not at the level of that IPv4 has. This specifically concerns the areas that are IPv6 specific, for example, related to neighbor discovery protocol (ND), stateless address autoconfiguration (SLAAC), subscriber identification, and security. While the standards are already mostly in place the implementations in deployed equipment can be lacking or inadequate for commercial deployments. This is largely only an issue with old existing equipment.

Class and quality of service capabilities (M)

The traffic class field of the fixed IPv6 header is designed for this purpose.

Packet traceability (M/W/N)

The traceability of replicated packets involves the capability to resolve which replication point issued a particular copy of a packet, which segment was intended for that replica, and which particular packet of which particular flow this is. Sequence also depends on the sequencing mechanism. As an example, the replication point may be indicated as the source of the packet if IP-in-IP encapsulation is used to forward along segments. Another alternate to IP-in-IP tunneling along segments would be to protect the original source address in a destination option similar to the Home Address option [RFC6275] and then use the address of the replication point as source in the IP header.

The traceability also involves the capability to determine if a particular segment is operational. While IPv6 as such has no support for reversing a path, it appears source route extensions such as the one defined for segment routing could be used for tracing purposes. Though it is not a usual practice, IPv6 [RFC2460] expects that a Source Route path may be reversed, and the standard insists that a node must not include the reverse of a Routing Header in the response unless the received Routing Header was authenticated.

Technical maturity (M/W)

IPv6 has been around about 20 years. However, large scale global and commercial IPv6 deployments are rather new dating only few years back to around 2012. While IPv6 has proven itself there are number of small issues to work on as they show up once operations experience grows.

The Cisco 6Lab site provides information on IPv6 deployment per country, indicating figures for prefixes, transit AS, content and users. Per this site, many countries, including Canada, Brazil, the USA, Germany, France, Japan, Portugal, Sweden, Finland, Norway, Greece, and Ecuador, achieve a deployment ratio above 30 percent, and the overall adoption reported by Google Statistics is now above 10 percent. Summary


4.1.2. Native IPv4 transport Solution description

IPv4 [RFC0791] is in principle the same as IPv6, except that it has a smaller address space. However, IPv6 was designed around the fact that extension headers are an integral part of the protocol and operation from the beginning, although the practice may some times prove differently [I-D.ietf-v6ops-ipv6-ehs-in-real-world]. IPv4 never really needed any extension headers to work properly, thus support for IPv4 options outside closed networks cannot typically be guaranteed. In the context of deterministic networking data plane solutions the major difference between IPv4 and IPv6 seems to be the practical support for header extensibility. Anything below and above the IP header independent of the version is practically the same. Analysis and Discussion

Encapsulation and overhead (M)

The fixed header of an IPv4 packet is 20 bytes [RFC0791]. IP options add overhead and the maximum IPv4 header size if 60 octets leaving only 40 octets for possible options.

Flow identification (W/N)

The IPv4 header has a 16-bit identification field that was originally intended for assisting fragmentation and reassembly of IPv4 packets as described in [RFC0791]. The identification field has also been proposed to be used for actually identifying flows between two IP addresses and a given protocol for detecting and removing duplicate packets [RFC1122]. However, recent update [RFC6864] to both [RFC0791] and [RFC1122] restricts the use of IPv4 identification field only to fragmentation purposes.

The IPv4 also has a stream identifier option [RFC0791], which contains a 16-bit SATNET stream identifier. However, the option has been deprecated [RFC6814]. The conclusion is that stream identification does not work nicely with IPv4 header alone and a traditional 5-tuple identification might not also be enough in a case of a flow duplication. For a working solution upper layer protocol headers such as the RTP are required for unambiguous flow identification.

Explicit routes (M/W)

IPv4 has two source routing option specified: the loose source and record route option (LSRR), and the strict source and record route option (SSRR) [RFC0791]. The support of these options in the Internet is questionable but within a closed network the support may be assumed.

Packet replication (W/N)

The functionality of replicating a packet exists in IPv4 but is limited to multicast flows. In general the issue regarding the IPv6 packet replication also applies to IPv4. Duplicate packet detection for IPv4 is studied in [RFC6621] to a great detail in the context of simplified multicast forwarding.

Operations, Administration and Maintenance (M)

IPv4 enjoys the extensive and "complete" existing toolbox for generic IP network management.

Class and quality of service capabilities (M)

The type of service (TOS) field of the fixed IPv4 header is designed for this purpose.

Packet traceability (W/N)

The IPv4 has a traceroute option [RFC1393] that could be used to record the route the packet took. However, the option has been deprecated [RFC6814]. Similarly to IPv6 new work would be needed to allow better traceability of IPv4 packets.

Technical maturity (M/W)

IPv4 can be considered mature technology with over 30 years of implementation, deployment and operations experience. However, no new IPv4 standards development is "allowed" anymore [RFC6540][I-D.ietf-sunset4-gapanalysis]. Summary


4.1.3. Multiprotocol Label Switching (MPLS) Solution description

Multiprotocol Label Switching Architecture (MPLS) [RFC3031] and its variants, MPLS with Traffic Engineering (MPLS-TE) [RFC3209] and [RFC3473], and MPLS Transport Profile (MPLS-TP) [RFC5921] is a widely deployed technology that switches traffic based on MPLS label stacks [RFC3032] and [RFC5960]. MPLS is the foundation for Pseudowire-based services Section 4.2.5 and emerging technologies such as Bit-Indexed Explicit Replication (BIER) Section and Source Packet Routing.

MPLS supports the equivalent of both the DetNet Service and DetNet Transport layers, and provides a very rich set of mechanisms that can be reused directly, and perhaps augmented in certain cases, to deliver DetNet services. At the DetNet Transport layer, MPLS provides forwarding, protection and OAM services. At the DetNet Service Layer it provides client service adaption, directly, via Pseudowires Section 4.2.5 and via other label-like mechanisms such as EPVN Section 4.2.6. A representation of these options are shown in Figure 3.

   PW-Based               EVPN Labeled                 IP
   Services                  Services                Transport
 |------------|  |-----------------------------|  |------------|

   Emulated       EVPN over LSP   EVPN w/ ESI ID        IP
                                  |  Payload   |
 +------------+   +------------+  +------------+             (Service)
 | PW Payload |   |  Payload   |  |ESI Lbl(S=1)|
 +------------+   +------------+  +------------+  +------------+
 |PW Lbl(S=1) |   |VPN Lbl(S=1)|  |VPN Lbl(S=0)|  |     IP     |
 |LSP Lbl(S=0)|   |LSP Lbl(S=0)|  |LSP Lbl(S=0)|  |LSP Lbl(S=1)|
 +------------+   +------------+  +------------+  +------------+
       .                .               .               .
       .                .               .               .    (Transport)
       .                .               .               .

~~~~~~~~~~~ denotes DetNet Service <-> DetNet Transport layer boundary

Figure 3: MPLS-based Services

MPLS can be controlled in a number of ways including via a control plane, via the management plane, or via centralized controller (SDN) based approaches. MPLS also provides standard control plane reference points. Additional information on MPLS architecture and control can be found in [RFC5921]. A summary of MPLS control plane related functions can be found in [RFC6373]. The remainder of this section will focus [RFC6373]. The remainder of this section will focus on the MPLS transport data plane, additional information on the MPLS service data plane can be found below in Section 4.2.4.

The following is a work in progress and draws heavily from [RFC5960] and may be updated, replaced or removed.

Encapsulation and forwarding of packets traversing MPLS LSPs follows standard MPLS packet encapsulation and forwarding as defined in [RFC3031], [RFC3032], [RFC5331], and [RFC5332].

Data plane Quality of Service capabilities are included in the MPLS in the form of Traffic Engineered (TE) LSPs [RFC3209] and the MPLS Differentiated Services (DiffServ) architecture [RFC3270]. Both E-LSP and L-LSP MPLS DiffServ modes are defined. The Traffic Class field (formerly the EXP field) of an MPLS label follows the definition of [RFC5462] and [RFC3270].

Except for transient packet reordering that may occur, for example, during fault conditions, packets are delivered in order on L-LSPs, and on E-LSPs within a specific ordered aggregate.

The Uniform, Pipe, and Short Pipe DiffServ tunneling and TTL processing models are described in [RFC3270] and [RFC3443] and may be used for MPLS LSPs.

Equal-Cost Multi-Path (ECMP) load-balancing is possible with MPLS LSPs and can be avoided using a number of techniques. The same holds for Penultimate Hop Popping (PHP).

MPLS includes the following LSP types:

o Point-to-point unidirectional

o Point-to-point associated bidirectional

o Point-to-point co-routed bidirectional

o Point-to-multipoint unidirectional

Point-to-point unidirectional LSPs are supported by the basic MPLS architecture [RFC3031].

A point-to-point associated bidirectional LSP between LSRs A and B consists of two unidirectional point-to-point LSPs, one from A to B and the other from B to A, which are regarded as a pair providing a single logical bidirectional transport path.

A point-to-point co-routed bidirectional LSP is a point-to-point associated bidirectional LSP with the additional constraint that its two unidirectional component LSPs in each direction follow the same path (in terms of both nodes and links). An important property of co-routed bidirectional LSPs is that their unidirectional component LSPs share fate.

A point-to-multipoint unidirectional LSP functions in the same manner in the data plane, with respect to basic label processing and packet-switching operations, as a point-to-point unidirectional LSP, with one difference: an LSR may have more than one (egress interface, outgoing label) pair associated with the LSP, and any packet it transmits on the LSP is transmitted out all associated egress interfaces. Point-to-multipoint LSPs are described in [RFC4875] and [RFC5332]. TTL processing and exception handling for point-to- multipoint LSPs is the same as for point-to-point LSPs.

Additional data plane capabilities include Linear Protection, [RFC6378] and [RFC7271]. And the in progress work on MPLS support for time synchronization [I-D.ietf-mpls-residence-time]. Analysis and Discussion

#? DetNet Service Interface (M)

The DetNet service interface is enabled through the DetNet Service Layer it provides client service adaption, directly, via Pseudowires Section 4.2.5 and via other label-like mechanisms such as EPVN Section 4.2.6.

#1 Encapsulation and overhead (M)

There are two perspectives to consider when looking at encapsulation. The first is encapsulation to support services. These considerations are part of the DetNet service layer and are covered below, see Sections 4.2.5 and 4.2.6.

The second perspective relates to encapsulation, if any, is needed to transport packets across network. In this case, the MPLS label stack, [RFC3032] is used to identify flows across a network. MPLS labels are compact and highly flexible. They can be stacked to support client adaptation, protection, network layering, source routing, etc.

#2 Flow identification (M)

MPLS label stacks provide highly flexible ways to identify flows. Basically, they enable the complete separation of traffic classification from traffic treatment and thereby enable arbitrary combinations of both.

#3 Packet sequencing (M)

Packet ordering in MPLS is generally similar to packet ordering in Ethernet. MPLS implementations can also support ECMP for certain types of traffic which can to lead to out of order delivery. There are defined techniques to avoid ECMP and ensure in order delivery during normal operation. Out of order delivery is still possible in certain MPLS protection scenarios. If additional ordering mechanisms are required, these are likely to be implemented at the DetNet Service Layer.

#4 Explicit routes (M)

MPLS supports explicit routes based on how LSPs are established, e.g., via TE explicit routes [RFC3209]. Additional, but not required, additional capabilities are being defined as part of Segment Routing (SR) [I-D.ietf-spring-segment-routing].

#5 Packet replication and deletion (M/W)

At the MPLS LSP level, there are mechanisms defined to provide 1+1 protection. The current definitions [RFC6378] and [RFC7271] use OAM mechanisms to support and coordinate protection switching and packet loss is possible during a switch. While such this level of protection may be sufficient for man DetNet applications, when truly hitless (i.e., zero loss) switching is required additional mechanisms will be needed. It is expected that these additional mechanisms will be defined at the DetNet Service Layer.

#6 Operations, Administration and Maintenance (M)

MPLS already includes a rich set of OAM functions at both the Service and Transport Layers. This includes LSP ping [ref] and those enabled via the MPLS Generic Associated Channel [RFC5586] and registered by IANA.

#7 Time synchronization (M/W)

MPLS itself does not provide any time synchronization service. The expectations is that the actual time-based scheduling will be provided by the sub-network layer, e.g., by [TSNTG], and that the DetNet transport layer will merely need to facilitate time synchronization (with hardware support) across multiple sub-network domains and technologies. Work is in progress [I-D.ietf-mpls-residence-time] that may satisfy, or serve as a building block for, DetNet time synchronization.

#8 Class and quality of service capabilities (M/W)

As previously mentioned, Data plane Quality of Service capabilities are included in the MPLS in the form of Traffic Engineered (TE) LSPs [RFC3209] and the MPLS Differentiated Services (DiffServ) architecture [RFC3270]. Both E-LSP and L-LSP MPLS DiffServ modes are defined. The Traffic Class field (formerly the EXP field) of an MPLS label follows the definition of [RFC5462] and [RFC3270]. One potential open area of work is synchronized, time based scheduling.

#9 Packet traceability (M)

MPLS supports multiple tracing mechanisms. A control based one is defined in [RFC3209]. An OAM based mechanism is defined in MPLS On-Demand Connectivity Verification and Route Tracing [RFC6426].

#10 Technical maturity (M)

MPLS as a mature technology that has been widely deployed in many networks for many years. Numerous vendor products and multiple generations of MPLS hardware have been built and deployed. Summary

MPLS is a mature technology that has been widely deployed. Numerous vendor products and multiple generations of MPLS hardware have been built and deployed. MPLS LSPs support a significant portion of the identified DetNet data plane criteria today. Aspects of the DetNet data plane that are not fully supported can be incrementally added.

4.2. DetNet Service layer technologies

4.2.1. Generic Routing Encapsulation (GRE) Solution description

Generic Routing Encapsulation (GRE) [RFC2784] provides an encapsulation of an arbitrary network layer protocol over another arbitrary network layer protocol. The encapsulation of a GRE packet can be found in Figure 4.

|                               |
|        Delivery Header        |
|                               |
|                               |
|          GRE Header           |
|                               |
|                               |
|         Payload packet        |
|                               |

Figure 4: Encapsulation of a GRE packet

Based on RFC2784, [RFC2890] further includes sequencing number and Key in optional fields of the GRE header, which may help to transport DetNet traffic flows over IP networks. The format of a GRE header is presented in Figure 5.

 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
 |C| |K|S|  Reserved0      | Ver |          Protocol Type          |
 |      Checksum (optional)      |        Reserved1 (Optional)     |
 |                        Key (optional)                           |
 |                  Sequence Number (optional)                     |

Figure 5: Format of a GRE header Analysis and Discussion

Encapsulation and overhead (M)

GRE provides encapsulation for a network layer protocol over anther network layer protocol. A new protocol type for DetNet traffics should be allocated as an "Ether Type" in [RFC1700] and in IANA Ethernet Numbers. The fixed header of a GRE packet is 4 octets while the maximum header is 16 octets with optional fields in Figure 5.

Flow identification (W)

There is no flow identification field in GRE header. However, it can rely on the flow identification mechanism applied in the delivery protocols, such as flow identification stated in IP Sections 4.1.1 and 4.1.2 when the delivery protocols are IPv6 and IPv4 respectively. Alternatively, the Key field can also be extended to carry the flow identification. The size of Key field is 4 octets.

Packet sequencing (M)

As stated in Section 4.2.1, GRE provides an optional sequencing number in its header to provide sequencing services for packets. The size of the sequencing number is 32 bits.

Duplicate packet deletion (N)

GRE has no packet replication and deletion currently in its header and should be extended or rely on delivery protocols.

Operations, Administration and Maintenance (W/N)

[note: rely on the delivery protocol] GRE has no packet replication and deletion currently and should be relied on delivery protocols.

Time synchronization (W/N)

[note: rely on the delivery protocol] GRE has no packet replication and deletion currently and should be relied on delivery protocols.

Class and quality of service capabilities (W/N)

[note: rely on the delivery protocol] GRE has no packet replication and deletion currently and should be relied on delivery protocols. For the class of service capability, an optional code point field to indicate CoS of a traffic can be extended in GRE header.

Technical maturity (M)

GRE has been developed over 20 years. The delivery protocol mostly used is IPv4, while the IPv6 support for GRE is to be standardized now in IETF as [I-D.ietf-intarea-gre-ipv6]. Due to its good extensibility, GRE is also extended to support network virtualization in Data Center, which is NVGRE [RFC7637]. Summary


4.2.2. Layer-2 Tunneling Protocol (L2TP)

[Editor's note: L2TPv3 [RFC3931] content to be provided later, if needed]

4.2.3. Virtual Extensible LAN (VXLAN)

[Editor's note: VXLAN [RFC7348] content to be provided later, if needed]

4.2.4. MPLS-based Services Solution description

MPLS supports the equivalent of both the DetNet Service and DetNet Transport layers. This, as well as a general overview of MPLS, is covered above in Section 4.1.3. This section will focus on the DetNet Service Layer it provides client service adaption, via Pseudowires in Section 4.2.5 and via native and other label-like mechanisms such as EPVN in Section 4.2.6. A representation of these options was previously discussed and is shown in Figure 3. Analysis and Discussion

#? DetNet Service Interface (M)

The following text is adapted from [RFC5921]:

The MPLS native service adaptation functions interface the client layer network service to MPLS. For Pseudowires, these adaptation functions are the payload encapsulation described in Section 4.4 of [RFC3985] and Section 6 of [RFC5659]. For network layer client services, the adaptation function uses the MPLS encapsulation format as defined in [RFC3032].

The purpose of this encapsulation is to abstract the data plane of the client layer network from the MPLS data plane, thus contributing to the independent operation of the MPLS network.

MPLS may itself be a client of an underlying server layer. MPLS can thus also bounded by a set of adaptation functions to this server layer network, which may itself be MPLS. These adaptation functions provide encapsulation of the MPLS frames and for the transparent transport of those frames over the server layer network.

While MPLS service can provided on and true end-system to end-system basis, it's more likely that DetNet service will be provided over Pseudowires as described in Section 4.2.5 or via an EPVN-based service described in Section 4.2.6 .

#1 Encapsulation and overhead (M)

MPLS labels in the label stack may be used to identify transport paths, see Section 4.1.3, or as service identifiers. Typically a single label is used for service identification. Additional details on how client adaptation makes use of such labels is part of actual client-related adaptation processing, see Sections 4.2.5 and 4.2.6.

#2 Flow identification (M)

This is basically the same as MPLS at the DetNet transport layer. MPLS label stacks provide highly flexible ways to identify flows. Basically, they enable the complete separation of traffic classification from traffic treatment and thereby enable arbitrary combinations of both. Typically a separate label will be added per service being supported by a node.

#3 Packet sequencing (M)

This is the same as MPLS at the DetNet transport layer. If additional ordering mechanisms are required, these will be needed (and added) in client-related adaptation processing, see Sections 4.2.5 and 4.2.6.

#4 Explicit routes (N/A)

Explicit routes are part of the DetNet transport layer, see Section 4.2.6, or as part of multi-segment PWEs, Section 4.2.5.

#5 Packet replication and deletion (M/W)

This is the same as MPLS at the DetNet transport layer. Additional capability may also be provided as part of client-related adaptation processing see Section 4.2.5.

#6 Operations, Administration and Maintenance (M)

This is the same as MPLS at the DetNet transport layer. Additional capability may also be provided as part of client-related adaptation processing.

#7 Time synchronization (TBD)

It's unclear at this time if any additional capability is needed at this level.

#8 Class and quality of service capabilities (M/W)

The MPLS client inherits its Quality of Service (QoS) from the MPLS transport layer, which in turn inherits its QoS from the server (sub-network) layer. The server layer therefore needs to provide the necessary QoS to ensure that the MPLS client QoS commitments can be satisfied.

#9 Packet traceability (M)

This is the same as MPLS at the DetNet transport layer.

#10 Technical maturity (M)

This is the same as MPLS at the DetNet transport layer. Summary

This is the same as MPLS at the DetNet transport layer. MPLS is a mature technology that has been widely deployed. Numerous vendor products and multiple generations of MPLS hardware have been built and deployed. MPLS LSPs support a significant portion of the identified DetNet data plane criteria today. Aspects of the DetNet data plane that are not fully supported can be incrementally added.

4.2.5. Pseudo Wire Emulation Edge-to-Edge (PWE3) Solution description

PSeudo Wire Emulation Edge-to-Edge (PWE3) [RFC3985] or simply PseudoWires (PW) provide means of emulating the essential attributes and behaviour of a telecommunications service over a packet switched network (PSN) using IP or MPLS transport. In addition to traditional telecommunications services such as T1 line or Frame Relay, PWs also provide transport for Ethernet service [RFC4448] and for generic packet service [RFC6658]. Figure 6 illustrate the reference PWE3 stack model.

+----------------+                      +----------------+
|Emulated Service|                      |Emulated Service|
|(e.g., Eth, ...)|<= Emulated Service =>|(e.g., Eth, ...)|
+----------------+                      +----------------+
|    Payload     |                      |    Payload     | CW,
|  Encapsulation |<=== Pseudo Wire ====>|  Encapsulation | Timing,
|                |                      |                | Seq., ..
+----------------+                      +----------------+
|PW Demultiplexer|                      |PW Demultiplexer|
|   PSN Tunnel,  |<==== PSN Tunnel ====>|  PSN Tunnel,   | MPLS.
| PSN & Physical |                      | PSN & Physical | L2TP,
|     Layers     |                      |    Layers      | IP, ..
+-------+--------+     ___________      +---------+------+
        |             /           \               |
        +============/     PSN     \==============+
                     \             /

Figure 6: PWE3 protocol stack reference model

PWs appear as a good data plane solution alternative for a number of reasons. PWs are a proven and deployed technology with a rich OAM control plane [RFC4447], and enjoy the toolbox developed for MPLS networks. Furthermore, PWs may have an optional Control Word (CW) as part of the payload encapsulation between the PSN and the emulated service that is, for example, capable of frame sequencing and duplicate detection. The encapsulation layer may also provide timing [RFC5087].

PWs can be also used if the PSN is IP, which enables the application of PWs in networks that do not have MPLS enabled in their core routers. One approach to provide PWs over IP is to provide MPLS over IP in some way and then leverage what is available for PWs over MPLS. The following standard solutions are available both for IPv4 and IPv6 to follow this approach. The different solutions have different overhead as discussed in the following subsection. The MPLS-in-IP encapsulation is specified by [RFC4023]. The IPv4 Protocol Number field or the IPv6 Next Header field is set to 137, which indicates an MPLS unicast packet. (The use of the MPLS-in-IP encapsulation for MPLS multicast packets is not supported.) The MPLS-in-GRE encapsulation is specified in [RFC4023], where the IP header (either IPv4 or IPv6) is followed by a GRE header, which is followed by an MPLS label stack. The protocol type field in the GRE header is set to MPLS Unicast (0x8847) or Multicast (0x8848). MPLS over L2TPv3 over IP encapsulation is specified by [RFC4817]. The MPLS-in-UDP encapsulation is specified by [RFC7510], where the UDP Destination Port indicates tunneled MPLS packet and the UDP Source Port is an entropy value that is generated by the encapsulator to uniquely identify a flow. MPLS-in-UDP encapsulation can be applied to enable UDP-based ECMP (Equal-Cost Multipath) or Link Aggregation. All these solutions can be secured with IPSec. Analysis and Discussion

Encapsulation and overhead (M)

PWs offer encapsulation services practically for any types of payloads over any PSN. New PW types need a code point allocation [RFC4446] and in some cases an emulated service specific document.

Specifically in the case of the MPLS PSN the PW encapsulation overhead is minimal. Typically minimum two labels and a CW is needed, which totals to 12 octets. PW type specific handling might, however, allow optimizations on the emulated service in the provider edge (PE) device's native service processing (NSP) / forwarder function. These optimizations could be used, for example, to reduce header overhead. Ethernet PWs already have rather low overhead [RFC4448]. Without a CW and VLAN tags the Ethernet header gets reduced to 14 octets (minimum Ethernet header overhead is 26).

The overhead is somewhat bigger in case of IP PSN if an MPLS over IP solution is applied to provide PWs. IP adds at least 20 (IPv4) or 40 (IPv6) bytes overhead to the PW over MPLS overhead; furthermore, the GRE, L2TPv3, or UDP header has to be taken into account if any of these further encapsulations is used.

Flow identification (M)

[Editor's note: this criteria has not been checked against the latest view of flow identification after the separation of transport and service layers.]

PWs provide multiple layers of flow identification, especially in the case of the MPLS PSN. The PWs are typically prepended with a PW label that can be used to identify a specific PW. Furthermore, the PSN also uses one or more labels to transport packets over a specific label switched paths (that then would carry PWs). IP (and other) PSNs may need other mechanisms, such as, UDP port numbers, upper layer protocol header (like RTP) or some IP extension header to provide required flow identification.

Packet sequencing (M)

As mentioned earlier PWs may contain an optional CW that is able to provide sequencing services. The size of the sequence number in the generic CW is 16 bits, which might be, depending on the used link and DetNet flow speed be too little.

Duplicate packet deletion (W)

The PW duplicate detection mechanism also exists in theory [RFC3985] but no emulated service makes use of it currently.

Operations, Administration and Maintenance (M/W)

PWs have rich control plane for OAM and in a case of the MPLS PSN enjoy the full control plane toolbox developed for MPLS network OAM likewise IP PSN have the full toolbox of IP network OAM tools. There could be, however, need for deterministic networking specific extensions for the mentioned control planes.

Time synchronization (M/W)

It is possible to carry time synchronization information as part of the PW encapsulation layer (see for example [RFC5087]). Whether the timing precision is enough for all deterministic networking use cases vary, and it is possible existing mechanisms are not adequate for all use cases. IP PSNs have already demonstrated the use of time synchronization as a part of PWE3 [RFC5086].

Class and quality of service capabilities (M)

In a case of IP PSN the 6-bit differentiated services code point (DSCP) field can be used for indicating the class of service [RFC2474] and 2-bit field reserved for the explicit congestion notification (ECN) [RFC3168]. Similarly, in a case of MPLS PSN, there are 3-bit traffic class field (TC) [RFC5462] in the label reserved for for both Explicitly TC-encoded-PSC LSPs (E-LSP) [RFC3270] and ECN [RFC5129]. Due to the limited number of bits in the TC field, their use for QoS and ECN functions restricted and intended to be flexible. Although the QoS/CoS mechanism is already in place some clarifications may be required in the context of deterministic networking flows, for example, if some specific mapping between bit fields have to be done.

Technical maturity (M)

PWs, IP and MPLS are proven technologies with wide variety of deployments and years of operational experience. Furthermore, the estimated work for missing functionality (packet replication and deletion) does not appear to be extensive, since the existing protection mechanism already get close to what is needed from the deterministic networking data plane solution. Summary

PseudoWires appear to be a strong candidate as the deterministic networking data plane solution alternative for the DetNet Service layer. The strong points are the technical maturity and the extensive control plane for OAM. This holds specifically for MPLS-based PSN.

Extensions are required to realize the packet replication and duplicate detection features of the deterministic networking data plane.

4.2.6. MPLS-Based Ethernet VPN (EVPN) Solution description

MPLS-Based Ethernet VPN (EVPN), in the form documented in [RFC7432] and [RFC7209], is an increasingly popular approach to delivering MPLS-based Ethernet services and is designed to be the successor to Virtual Private LAN Service (VPLS), [RFC4664].

EVPN provides client adaptation and reuses the MPLS data plane discussed above in Section 4.2.4. In certain special cases, it also uses the PW MPLS Control Word. EVPN control is via BGP, [RFC7432], and may use TE-LSPs, e.g., controlled via [RFC3209] for MPLS transport. Additional EVPN related RFCs and in progress drafts are being developed by the BGP Enabled Services Working Group. Analysis and Discussion

#? DetNet Service Interface (M/W)

The service supported by EVPN is a layer 2 Ethernet virtual private network. While EVPN is typically envisioned to be deployed on provider edge systems, it is also possible to extent the EVPN service to a DetNet end or edge system if such service is needed.

#1 Encapsulation and overhead (M)

EVPN generally uses a single MPLS label stack entry to support its client adaptation service. The optional addition of a second label is also supported. In certain cases PW Control Word may also be used.

#2 Flow identification (W)

EVPN currently uses labels to identify flows per {Ethernet Segment Identifier, VLAN} or per MAC level. Additional definition will be needed to standardize identification of finer granularity DetNet flows.

#3 Packet sequencing (M/W)

Like MPLS, EVPN generally orders packets similar to Ethernet. Reordering is possible primarily during path changes and protection switching. In order to avoid misordering due to ECMP, EVPN uses the "Preferred PW MPLS Control Word" [RFC4385] or the entropy labels [RFC6790].

If additional ordering mechanisms are required, such mechanisms will need to be defined.

#4 Explicit routes (M)

EVPN itself doesn't offer support for explicit routes as it is simply an adaptation function. Explicit routes for EVPN at the DetNet transport layer would be provided via MPLS.

#5 Packet replication and deletion (M/W)

EVPN relies on the MPLS layer for all protection functions. See Section 4.1.3 and Section 4.2.4. Some extensions, either at the EVPN or MPLS levels, will be need to support those DetNet applications which require true hitless (i.e., zero loss) 1+1 protection switching. (Network coding may be an interesting alternative to investigate to delivering such hitless loss protection capability.)

#6 Operations, Administration and Maintenance (M/W)

Nodes supporting EVPN may participate in either or both Ethernet level and MPLS level OAM. It is likely that it may make sense to map or adapt the OAM functions at the different levels, but such has yet to be defined. [RFC6371] provides some useful background on this topic.

#7 Time synchronization (W)

The interface to the DetNet time synchronization service is still to be determined. If the service is accessed by end systems via IEEE defined mechanisms, then those mechanisms will need to be mapped to the MPLS provided mechanisms discussed in Section 4.1.3.

#8 Class and quality of service capabilities (M/W)

EVPN is largely silent on the topics of CoS and QoS, but the existing Ethernet and MPLS mechanisms can be directly used. While an implementation may support such mappings today, standardized mappings do not (yet) exist.

#9 Packet traceability (M)

EVPN nodes can utilize MPLS layers tracing mechanisms.

#10 Technical maturity

EVPN is a second (or third) generation MPLS-based L2VPN service standard. From a data plane standpoint it makes uses of existing MPLS data plane mechanisms. The mechanisms have been widely implemented and deployed. Summary

EVPN is the emerging successor to VPLS. EVPN is standardized, implemented and deployed. It makes use of the mature MPLS data plane. While offering a mature and very comprehensive set of features, certain DetNet required features are not fully/directly supported and additional standardization in these areas are needed. Examples include: mapping CoS and QoS; use of labels per DetNet flow, and hitless 1+1 protection.

4.2.7. Bit Indexed Explicit Replication (BIER)

Bit Indexed Explicit Replication [I-D.ietf-bier-architecture] (BIER) is a network plane replication technique that was initially intended as a new method for multicast distribution. In a nutshell, a BIER header includes a bitmap that explicitly signals the listeners that are intended for a particular packet, which means that 1) the sender is aware of the individual listeners and 2) the BIER control plane is a simple extension of the unicast routing as opposed to a dedicated multicast data plane, which represents a considerable reduction in OPEX. For this reason, the technology faces a lot of traction from Service Providers. Section discusses the applicability of BIER for replication in the DetNet.

The simplicity of the BIER technology makes it very versatile as a network plane signaling protocol. Already, a new Traffic Engineering variation is emerging that uses bits to signal segments along a TE path. While the more classical BIER is mainly a multicast technology that typically leverages a unicast distributed control plane through IGP extensions, BIER-TE is mainly a unicast technology that leverages a central computation to setup path, compute segments and install the mapping in the intermediate nodes. Section discusses the applicability of BIER-TE for replication, traceability and OAM operations in DetNet. Base BIER

Bit-Indexed Explicit Replication (BIER) layer may be considered to be included into Deterministic Networking data plane solution. Encapsulation of a BIER packet in MPLS network presented in Figure 7

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
|                   Label Stack Element                         |
|                   Label Stack Element                         |
|              BIER-MPLS label          |     |1|               |
|0 1 0 1|  Ver  |  Len  |              Entropy                  |
|                BitString  (first 32 bits)                     ~
~                                                               ~
~                BitString  (last 32 bits)                      |
|OAM|     Reserved      | Proto |            BFIR-id            |

Figure 7: BIER packet in MPLS encapsulation Solution description

The DetNet may be presented in BIER as distinctive payload type with its own Proto(col) ID. Then it is likely that DetNet will have the header that would identify:

  • Version;
  • Sequence Number;
  • Timestamp;
  • Payload type, e.g. data vs. OAM.

DetNet node, collocated with BFIR, may use multiple BIER sub-domains to create replicated flows. Downstream DetNet nodes, collocated with BFER, would terminate redundant flows based on Sequence Number and/or Timestamp information. Such DetNet may be BFER in one BIER sub-domain and BFIR in another. Thus DetNet flow would traverse several BIER sub-domains.

                   |  A  |
                    /   \
                   .     .
                  /       .
                 .         \
                /           .
               .             .
              /               \
         +-----+             +-----+
         |  B  |             |  C  |
         +-----+             +-----+
          /   \               /   \
         .     .             .     .
        /       \           .       .
       .         .         /         \
      /           \       .           .
     .             .     .             .
    /               \   /               \
+-----+            +-----+           +-----+
|  D  |            |  E  |           |  F  |
+-----+            +-----+           +-----+
   \                .  .               /
    .              .    .             .
     \            .      .           .
      .          .        .         / 
       \        .          .       .
         .     .            .     .
          \   .              .   / 
         +-----+            +-----+
         |  G  |            |  H  |
         +-----+            +-----+

Figure 8: DetNet in BIER domain

Consider DetNet flow that must traverse BIER enabled domain from A to G and H. DetNet may use three BIER subdomains:

  • A-B-D-E-G (dash-dot): A is BFIR, E and G are BFERs,
  • A-C-E-F-H (dash-double-dot): A is BFIR, E and H are BFERs,
  • E-G-H (dotted): E is BFIR, G and H are BFERs.

DetNet node A sends DetNet into red and purple BIER sub-domains. DetNet node E receives DetNet packet and sends into green sub-domain while terminating duplicates and those that deemed too-late.

DetNet nodes G and H receive DetNet flows, terminate duplicates and those that are too-late. Analysis and Discussion Summary BIER - Traffic Engineering

An alternate use of Bit-Indexed Explicit Replication (BIER) uses bits in the BitString to represent adjacencies as opposed to destinations, as discussed in BIER Traffic Engineering (TE) [I-D.eckert-bier-te-arch].

The proposed function of BIER-TE in the DetNet data plane is to control the process of replication and elimination, as opposed to the identification of the flows or and the sequencing of packets within a flow.

At the path ingress, BIER-TE identifies the adjacencies that are activated for this packet (under the rule of the controller). At the egress, BIER-TE is used to identify the adjacencies where transmission failed. This information is passed to the controller, which in turn can modify the active adjacencies for the next packets.

The value is that the replication can be controlled and monitored with the granularity of a packet and a adjacency in a control loops that involves an external controller. Solution description

BIER-TE enables to activate the replication and elimination functions in a manner that is abstract to the data plane forwarding information. An adjacency, which is represented by a bit in the BIER header, can correspond in the data plane to an Ethernet hop, a Label Switched Path, or it can correspond to an IPv6 loose or strict source routed path.

In a nutshell, BIER-TE is used as follows:

  • A controller computes a complex path, sometimes called a track, which takes the general form of a ladder. The steps and the side rails between them are the adjacencies that can be activated on demand on a per-packet basis using bits in the BIER header.

                 ===> (A) ====> (C) ==== 
               //     ^ |       ^ |     \\
   ingress (I)        | |       | |       (E) egress
               \\     | v       | v     //
                 ===> (B) ====> (D) ==== 

Figure 9: Ladder Shape with Replication and Elimination Points

  • The controller assigns a BIER domain, and inside that domain, assigns bits to the adjacencies. The controller assigns each bit to a replication node that sends towards the adjacency, for instance the ingress router into a segment that will insert a routing header in the packet. A single bit may be used for a step in the ladder, indicating the other end of the step in both directions.

                 ===> (A) ====> (C) ==== 
               // 1   ^ |  4    ^ |   7 \\
   ingress (I)        |2|       |6|       (E) egress
               \\ 3   | v  5    | v   8 //    
                 ===> (B) ====> (D) ==== 

Figure 10: Assigning Bits

  • The controller activates the replication by deciding the setting of the bits associated with the adjacencies. This decision can be modified at any time, but takes the latency of a controller round trip to effectively take place. Below is an example that uses Replication and Elimination to protect the A->C adjacency.

Controlling Replication
Bit # Adjacency Owner Example Bit Setting
1 I->A I 1
2 A->B A 1
B->A B
3 I->C I 0
4 A->C A 1
5 B->D B 1
6 C->D C 1
D->C D
7 C->E C 1
8 D->E D 0

Replication and Elimination Protecting A->C

  • The BIER header with the controlling BitString is injected in the packet by the ingress node of the deterministic path. That node may act as a replication point, in which case it may issue multiple copies of the packet

              ====>  Repl ===> Elim ==== 
           //         |         ^        \\
   ingress            |         |           egress
                      v         |             
                     Fwd ====> Fwd      

Figure 11: Enabled Adjacencies

  • For each of its bits that is set in the BIER header, the owner replication point resets the bit and transmits towards the associated adjacency; to achieve this, the replication point copies the packet and inserts the relevant data plane information, such as a source route header, towards the adjacency that corresponds to the bit

BIER-TE in Action
Adjacency BIER BitString
I->A 01011110
A->B 00011110
B->D 00010110
D->C 00010010
A->C 01001110

BitString in BIER Header as Packet Progresses

  • Adversely, an elimination node on the way strips the data plane information and performs a bitwise AND on the BitStrings from the various copies of the packet that it has received, before it forwards the packet with the resulting BitString.

BIER-TE in Action (cont.)
Operation BIER BitString
D->C 00010010
A->C 01001110
AND in C 00000010
C->E 00000000

BitString Processing at Elimination Point C

  • In this example, all the transmissions succeeded and the BitString at arrival has all the bits reset - note that the egress may be an Elimination Point in which case this is evaluated after this node has performed its AND operation on the received BitStrings).

BIER-TE in Action (cont.)
Failing Adjacency Egress BIER BitString
I->A Frame Lost
I->B Not Tried
A->C 00010000
A->B 01001100
B->D 01001100
D->C 01001100
C->E Frame Lost
D->E Not Tried

BitString indicating failures

  • But if a transmission failed along the way, one (or more) bit is never cleared. Table 4 provides the possible outcomes of a transmission. If the frame is lost, then it is probably due to a failure in either I->A or C->E, and the controller should enable I->B and D->E to find out. A BitString of 00010000 indicates unequivocally a transmission error on the A->C adjacency, and a BitString of 01001100 indicates a loss in either A->B, B->D or D->C; enabling D->E on the next packets may provide more information to sort things out.

In more details:

The BIER header is of variable size, and a DetNet network of a limited size can use a model with 64 bits if 64 adjacencies are enough, whereas a larger deployment may be able to signal up to 256 adjacencies for use in very complex paths. Figure 7 illustrates a BIER header as encapsulated within MPLS. The format of this header is common to BIER and BIER-TE.

For the DetNet data plane, a replication point is an ingress point for more than one adjacency, and an elimination point is an egress point for more than one adjacency.

A pre-populated state in a replication node indicates which bits are served by this node and to which adjacency each of these bits corresponds. With DetNet, the state is typically installed by a controller entity such as a PCE. The way the adjacency is signaled in the packet is fully abstracted in the bit representation and must be provisioned to the replication nodes and maintained as a local state, together with the timing or shaping information for the associated flow.

The DetNet data plane uses BIER-TE to control which adjacencies are used for a given packet. This is signaled from the path ingress, which sets the appropriate bits in the BIER BitString to indicate which replication must happen.

The replication point clears the bit associated to the adjacency where the replica is placed, and the elimination points perform a logical AND of the BitStrings of the copies that it gets before forwarding.

As is apparent in the examples above, clearing the bits enables to trace a packet to the replication points that made any particular copy. BIER-TE also enables to detect the failing adjacencies or sequences of adjacencies along a path and to activate additional replications to counter balance the failures.

Finally, using the same BIER-TE bit for both directions of the steps of the ladder enables to avoid replication in both directions along the crossing adjacencies. At the time of sending along the step of the ladder, the bit may have been already reset by performing the AND operation with the copy from the other side, in which case the transmission is not needed and does not occur (since the control bit is now off).

4.2.8. Higher layer header fields

Fields of headers belonging to higher OSI layers can be used to implement functionality that is not provided e.g., by the IPv6 or IPv4 header fields. However, this approach cannot be always applied, e.g., due to encryption. Furthermore, even if this approach is applicable, it requires deep packet inspection from the routers and switches. There are implementation dependent limits how far into the packet the lookup can be done efficiently in the fast path. In general a safe bet is between 128 and 256 octets for the maximum lookup depth. Various higher layer protocols can be applied. Some examples are provided here for the sequence numbering feature (Section 3.4). TCP

The TCP header includes a sequence number parameter, which can be applied to detect and eliminate duplicate packets if seamless redundancy is used. As the TCP header is right after the IP header, it does not require very deep packet inspection; the 4-byte sequence number is conveyed by bits 32 through 63 of the TCP header. In addition to sequencing, the TCP header also contain source and destination port information that can be used for assisting the flow identification. RTP

RTP is often used to deliver time critical traffic in IP networks. RTP is is carried on top of IP and UDP [RFC3550]. The RTP header includes a 2-byte sequence number, which can be used to detect and eliminate duplicate packets if seamless redundancy is used. The sequence number is conveyed by bits 16 through 31 of the RTP header. In addition to the sequence number the RTP header has also timestamp field (bits 32 through 63) that can be useful for time synchronization purposes. Furthermore, the RTP header has also one or more synchronization sources (bits starting from 64) that can potentially be useful for flow identification purposes.

5. Summary of data plane alternatives


6. Security considerations


7. IANA Considerations

This document has no IANA considerations.

8. Acknowledgements

The author(s) ACK and NACK.

The following people were part of the DetNet Data Plane Design Team:

  • Jouni Korhonen
  • János Farkas
  • Norman Finn
  • Olivier Marce
  • Gregory Mirsky
  • Pascal Thubert
  • Zhuangyan Zhuang

The DetNet chairs serving during the DetNet Data Plane Design Team:

  • Lou Berger
  • Pat Thaler

9. Informative References

[I-D.eckert-bier-te-arch] Eckert, T., Cauchie, G., Braun, W. and M. Menth, "Traffic Engineering for Bit Index Explicit Replication BIER-TE", Internet-Draft draft-eckert-bier-te-arch-03, March 2016.
[I-D.finn-detnet-architecture] Finn, N., Thubert, P. and M. Teener, "Deterministic Networking Architecture", Internet-Draft draft-finn-detnet-architecture-02, November 2015.
[I-D.finn-detnet-problem-statement] Finn, N. and P. Thubert, "Deterministic Networking Problem Statement", Internet-Draft draft-finn-detnet-problem-statement-04, October 2015.
[I-D.ietf-6man-rfc2460bis] Deering, S. and B. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", Internet-Draft draft-ietf-6man-rfc2460bis-04, March 2016.
[I-D.ietf-6man-segment-routing-header] Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova, J., Kosugi, T., Vyncke, E. and D. Lebrun, "IPv6 Segment Routing Header (SRH)", Internet-Draft draft-ietf-6man-segment-routing-header-01, March 2016.
[I-D.ietf-bier-architecture] Wijnands, I., Rosen, E., Dolganow, A., P, T. and S. Aldrin, "Multicast using Bit Index Explicit Replication", Internet-Draft draft-ietf-bier-architecture-03, January 2016.
[I-D.ietf-idr-ls-distribution] Gredler, H., Medved, J., Previdi, S., Farrel, A. and S. Ray, "North-Bound Distribution of Link-State and TE Information using BGP", Internet-Draft draft-ietf-idr-ls-distribution-13, October 2015.
[I-D.ietf-intarea-gre-ipv6] Pignataro, C., Bonica, R. and S. Krishnan, "IPv6 Support for Generic Routing Encapsulation (GRE)", Internet-Draft draft-ietf-intarea-gre-ipv6-14, September 2015.
[I-D.ietf-isis-pcr] Farkas, J., Bragg, N., Unbehagen, P., Parsons, G., Ashwood-Smith, P. and C. Bowers, "IS-IS Path Computation and Reservation", Internet-Draft draft-ietf-isis-pcr-05, February 2016.
[I-D.ietf-mpls-residence-time] Mirsky, G., Ruffini, S., Gray, E., Drake, J., Bryant, S. and S. Sasha, "Residence Time Measurement in MPLS network", Internet-Draft draft-ietf-mpls-residence-time-06, March 2016.
[I-D.ietf-spring-segment-routing] Filsfils, C., Previdi, S., Decraene, B., Litkowski, S. and R. Shakir, "Segment Routing Architecture", Internet-Draft draft-ietf-spring-segment-routing-07, December 2015.
[I-D.ietf-sunset4-gapanalysis] Perreault, S., Tsou, T., Zhou, C. and P. Fan, "Gap Analysis for IPv4 Sunset", Internet-Draft draft-ietf-sunset4-gapanalysis-07, April 2015.
[I-D.ietf-v6ops-ipv6-ehs-in-real-world] Gont, F., Linkova, J., Chown, T. and S. LIU, "Observations on the Dropping of Packets with IPv6 Extension Headers in the Real World", Internet-Draft draft-ietf-v6ops-ipv6-ehs-in-real-world-02, December 2015.
[IEEE802.1Qbv] IEEE, "Enhancements for Scheduled Traffic", 2016.
[IEEE802.1Qch] IEEE, "Cyclic Queuing and Forwarding", 2016.
[IEEE8021CB] Finn, N., "Draft Standard for Local and metropolitan area networks - Seamless Redundancy", IEEE P802.1CB /D2.1 P802.1CB, December 2015.
[IEEE8021Qca] IEEE 802.1, "IEEE 802.1Qca Bridges and Bridged Networks - Amendment 24: Path Control and Reservation", IEEE P802.1Qca/D2.1 P802.1Qca, June 2015.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, September 1981.
[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, DOI 10.17487/RFC1122, October 1989.
[RFC1393] Malkin, G., "Traceroute Using an IP Option", RFC 1393, DOI 10.17487/RFC1393, January 1993.
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, DOI 10.17487/RFC1700, October 1994.
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, September 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, December 1998.
[RFC2474] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, December 1998.
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, DOI 10.17487/RFC2702, September 1999.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D. and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, DOI 10.17487/RFC2784, March 2000.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE", RFC 2890, DOI 10.17487/RFC2890, September 2000.
[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T. and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001.
[RFC3168] Ramakrishnan, K., Floyd, S. and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, DOI 10.17487/RFC3168, September 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001.
[RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, P., Krishnan, R., Cheval, P. and J. Heinanen, "Multi-Protocol Label Switching (MPLS) Support of Differentiated Services", RFC 3270, DOI 10.17487/RFC3270, May 2002.
[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, DOI 10.17487/RFC3443, January 2003.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, DOI 10.17487/RFC3473, January 2003.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, July 2003.
[RFC3931] Lau, J., Townsley, M. and I. Goyret, "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, DOI 10.17487/RFC3931, March 2005.
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005.
[RFC4023] Worster, T., Rekhter, Y. and E. Rosen, "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005.
[RFC4385] Bryant, S., Swallow, G., Martini, L. and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, February 2006.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, DOI 10.17487/RFC4446, April 2006.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T. and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, DOI 10.17487/RFC4447, April 2006.
[RFC4448] Martini, L., Rosen, E., El-Aawar, N. and G. Heron, "Encapsulation Methods for Transport of Ethernet over MPLS Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006.
[RFC4664] Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, DOI 10.17487/RFC4664, September 2006.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T. and J. Young, "Encapsulation of MPLS over Layer 2 Tunneling Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March 2007.
[RFC4875] Aggarwal, R., Papadimitriou, D. and S. Yasukawa, "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 4875, DOI 10.17487/RFC4875, May 2007.
[RFC5086] Vainshtein, A., Sasson, I., Metz, E., Frost, T. and P. Pate, "Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007.
[RFC5087] Stein, Y(J)., Shashoua, R., Insler, R. and M. Anavi, "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, DOI 10.17487/RFC5087, December 2007.
[RFC5129] Davie, B., Briscoe, B. and J. Tay, "Explicit Congestion Marking in MPLS", RFC 5129, DOI 10.17487/RFC5129, January 2008.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008.
[RFC5331] Aggarwal, R., Rekhter, Y. and E. Rosen, "MPLS Upstream Label Assignment and Context-Specific Label Space", RFC 5331, DOI 10.17487/RFC5331, August 2008.
[RFC5332] Eckert, T., Rosen, E., Aggarwal, R. and Y. Rekhter, "MPLS Multicast Encapsulations", RFC 5332, DOI 10.17487/RFC5332, August 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 2009.
[RFC5586] Bocci, M., Vigoureux, M. and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-Segment Pseudowire Emulation Edge-to-Edge", RFC 5659, DOI 10.17487/RFC5659, October 2009.
[RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L. and L. Berger, "A Framework for MPLS in Transport Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010.
[RFC5960] Frost, D., Bryant, S. and M. Bocci, "MPLS Transport Profile Data Plane Architecture", RFC 5960, DOI 10.17487/RFC5960, August 2010.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M. and M. Aissaoui, "Segmented Pseudowire", RFC 6073, DOI 10.17487/RFC6073, January 2011.
[RFC6275] Perkins, C., Johnson, D. and J. Arkko, "Mobility Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 2011.
[RFC6371] Busi, I. and D. Allan, "Operations, Administration, and Maintenance Framework for MPLS-Based Transport Networks", RFC 6371, DOI 10.17487/RFC6371, September 2011.
[RFC6373] Andersson, L., Berger, L., Fang, L., Bitar, N. and E. Gray, "MPLS Transport Profile (MPLS-TP) Control Plane Framework", RFC 6373, DOI 10.17487/RFC6373, September 2011.
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N. and A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear Protection", RFC 6378, DOI 10.17487/RFC6378, October 2011.
[RFC6426] Gray, E., Bahadur, N., Boutros, S. and R. Aggarwal, "MPLS On-Demand Connectivity Verification and Route Tracing", RFC 6426, DOI 10.17487/RFC6426, November 2011.
[RFC6437] Amante, S., Carpenter, B., Jiang, S. and J. Rajahalme, "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/RFC6437, November 2011.
[RFC6540] George, W., Donley, C., Liljenstolpe, C. and L. Howard, "IPv6 Support Required for All IP-Capable Nodes", BCP 177, RFC 6540, DOI 10.17487/RFC6540, April 2012.
[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J. and M. Bhatia, "A Uniform Format for IPv6 Extension Headers", RFC 6564, DOI 10.17487/RFC6564, April 2012.
[RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621, DOI 10.17487/RFC6621, May 2012.
[RFC6658] Bryant, S., Martini, L., Swallow, G. and A. Malis, "Packet Pseudowire Encapsulation over an MPLS PSN", RFC 6658, DOI 10.17487/RFC6658, July 2012.
[RFC6718] Muley, P., Aissaoui, M. and M. Bocci, "Pseudowire Redundancy", RFC 6718, DOI 10.17487/RFC6718, August 2012.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J. and G. Zorn, "Diameter Base Protocol", RFC 6733, DOI 10.17487/RFC6733, October 2012.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W. and L. Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC 6790, DOI 10.17487/RFC6790, November 2012.
[RFC6814] Pignataro, C. and F. Gont, "Formally Deprecating Some IPv4 Options", RFC 6814, DOI 10.17487/RFC6814, November 2012.
[RFC6864] Touch, J., "Updated Specification of the IPv4 ID Field", RFC 6864, DOI 10.17487/RFC6864, February 2013.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing of IPv6 Extension Headers", RFC 7045, DOI 10.17487/RFC7045, December 2013.
[RFC7167] Frost, D., Bryant, S., Bocci, M. and L. Berger, "A Framework for Point-to-Multipoint MPLS in Transport Networks", RFC 7167, DOI 10.17487/RFC7167, April 2014.
[RFC7209] Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N., Henderickx, W. and A. Isaac, "Requirements for Ethernet VPN (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014.
[RFC7271] Ryoo, J., Gray, E., van Helvoort, H., D'Alessandro, A., Cheung, T. and E. Osborne, "MPLS Transport Profile (MPLS-TP) Linear Protection to Match the Operational Expectations of Synchronous Digital Hierarchy, Optical Transport Network, and Ethernet Transport Network Operators", RFC 7271, DOI 10.17487/RFC7271, June 2014.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger, L., Sridhar, T., Bursell, M. and C. Wright, "Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path Computation Element Architecture", RFC 7399, DOI 10.17487/RFC7399, October 2014.
[RFC7426] Haleplidis, E., Pentikousis, K., Denazis, S., Hadi Salim, J., Meyer, D. and O. Koufopavlou, "Software-Defined Networking (SDN): Layers and Architecture Terminology", RFC 7426, DOI 10.17487/RFC7426, January 2015.
[RFC7432] Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., Uttaro, J., Drake, J. and W. Henderickx, "BGP MPLS-Based Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R. and D. Black, "Encapsulating MPLS in UDP", RFC 7510, DOI 10.17487/RFC7510, April 2015.
[RFC7637] Garg, P. and Y. Wang, "NVGRE: Network Virtualization Using Generic Routing Encapsulation", RFC 7637, DOI 10.17487/RFC7637, September 2015.
[ST20227] SMPTE 2022, "Seamless Protection Switching of SMPTE ST 2022 IP Datagrams", ST 2022-7:2013, 2013.
[TSNTG] IEEE Standards Association, "IEEE 802.1 Time-Sensitive Networks Task Group", 2013.

Appendix A. Examples of combined DetNet Service and Transport layers

Authors' Addresses

Jouni Korhonen (editor) Broadcom 3151 Zanker Road San Jose, CA 95134 USA EMail:
János Farkas Ericsson Konyves Kálmán krt. 11/B Budapest, 1097 Hungary EMail:
Gregory Mirsky Ericsson EMail:
Pascal Thubert Cisco EMail:
Yan Zhuang Huawei EMail:
Lou Berger LabN Consulting, L.L.C. EMail: