| DetNet | J. Korhonen, Ed. |
| Internet-Draft | |
| Intended status: Standards Track | B. Varga, Ed. |
| Expires: April 24, 2019 | Ericsson |
| October 21, 2018 |
DetNet IP Data Plane Encapsulation
draft-ietf-detnet-dp-sol-ip-01
This document specifies Deterministic Networking data plane operation for IP encapsulated user data.
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Deterministic Networking (DetNet) is a service that can be offered by a network to DetNet flows. DetNet provides these flows extremely low packet loss rates and assured maximum end-to-end delivery latency. General background and concepts of DetNet can be found in the DetNet Architecture [I-D.ietf-detnet-architecture].
This document specifies the DetNet data plane operation for IP hosts and routers that provide DetNet service to IP encapsulated data. No DetNet specific encapsulation is defined to support IP flows, rather existing IP and higher layer protocol header information is used to support flow identification and DetNet service delivery.
The DetNet Architecture decomposes the DetNet related data plane functions into two layers: a service layer and a transport layer. The service layer is used to provide DetNet service protection and reordering. The transport layer is used to provides congestion protection (low loss, assured latency, and limited reordering). As no DetNet specific headers are added to support IP DetNet flows, only the transport layer functions are supported using the IP DetNet defined by this document. Service protection can be provided on a per sub-net basis using technologies such as MPLS [I-D.ietf-detnet-dp-sol-mpls] and IEEE802.1 TSN.
This document provides an overview of the DetNet IP data plane in Section 3, considerations that apply to providing DetNet services via the DetNet IP data plane in Section 4 and Section 5. Section 6 provides the procedures for hosts and routers that support IP-based DetNet services. Finally, Section 7 provides rules for mapping IP-based DetNet flows to IEEE 802.1 TSN streams.
This document uses the terminology and concepts established in the DetNet architecture [I-D.ietf-detnet-architecture] the reader is assumed to be familiar with that document.
The following abbreviations used in this document:
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
This document describes how IP is used by DetNet nodes, i.e., hosts and routers, to identify DetNet flows and provide a DetNet service. From a data plane perspective, an end-to-end IP model is followed. As mentioned above, existing IP and higher layer protocol header information is used to support flow identification and DetNet service delivery.
DetNet uses "6-tuple" based flow identification, where "6-tuple" refers to information carried in IP and higher layer protocol headers. General background on the use of IP headers, and "5-tuples", to identify flows and support Quality of Service (QoS) can be found in [RFC3670]. [RFC7657] also provides useful background on the delivery differentiated services (DiffServ) and "6-tuple" based flow identification.
DetNet flow aggregation may be enabled via the use of wildcards, masks, prefixes and ranges. IP tunnels may also be used to support flow aggregation. In these cases, it is expected that DetNet aware intermediate nodes will provide DetNet service assurance on the aggregate through resource allocation and congestion control mechanisms.
IP DetNet Relay Relay IP DetNet
End System Node Node End System
+---------+ +---------+
| Appl. |<--------------- End to End Service ---------->| Appl. |
+---------+ ........... ........... +---------+
| Service |<---: Service :-- DetNet flow ---: Service :-->| Service |
+---------+ +---------+ +---------+ +---------+
|Transport| |Transport| |Transport| |Transport|
+-------.-+ +-.-----.-+ +-.-----.-+ +---.-----+
: Link : \ ,-----. / / ,-----. \
+........+ +-----[ Sub ]----+ +-[ Sub ]-+
[Network] [Network]
`-----' `-----'
|<--------------------- DetNet IP -------------------->|
Figure 1: A Simple DetNet (DN) Enabled IP Network
Figure 1 illustrates a DetNet enabled IP network. The DetNet enabled end systems originate IP encapsulated traffic that is identified as DetNet flows, relay nodes understand the transport requirements of the DetNet flow and ensure that node, interface and sub-network resources are allocated to ensure DetNet service requirements. The dotted line around the Service component of the Relay Nodes indicates that the transit routers are DetNet service aware but do not perform any DetNet service layer function, e.g., PREOF. IEEE 802.1 TSN is an example sub-network type which can provide support for DetNet flows and service. The mapping of IP DetNet flows to TSN streams and TSN protection mechanisms is covered in Section 7.
Note: The sub-network can represent a TSN, MPLS or IP network segment.
IP DetNet Relay Transit Relay IP DetNet
End System Node Node Node End System
+---------+ +---------+
| Appl. |<--------------- End to End Service ---------->| Appl. |
+---------+ .....-----+ +-----..... +---------+
| Service |<---: Service |-- DetNet flow ---| Service :-->| Service |
| | : |<- DN MPLS flow ->| : | |
+---------+ +---------+ +---------+ +---------+ +---------+
|Transport| |Trp| |Trp| |Transport| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +---.---.-+ +-.-+ +-.-+ +---.-----+
: Link : / ,-----. \ : Link : / ,-----. \
+........+ +-[ Sub ]-+ +........+ +--[ Sub ]--+
[Network] [Network]
`-----' `-----'
|<---- DetNet MPLS ---->|
|<--------------------- DetNet IP -------------------->|
Figure 2: DetNet (DN) IP Over MPLS Network
Figure 2 illustrates a variant of Figure 1, with an MPLS based DetNet network as a sub-network between the relay nodes. It shows a more complex DetNet enabled IP network where an IP flow is mapped to one or more PWs and MPLS (TE) LSPs. The end systems still originate IP encapsulated traffic that is identified as DetNet flows. The relay nodes follow procedures defined in [I-D.ietf-detnet-dp-sol-mpls] to map each DetNet flow to MPLS LSPs. While not shown, relay nodes can provide service layer functions such as PREOF over the MPLS transport layer, and this is indicated by the solid line for the MPLS facing portion of the Service component. Note that the Transit node is MPLS (TE) LSP aware and performs switching based on MPLS labels, and need not have any specific knowledge of the DetNet service or the corresponding DetNet flow identification. See [I-D.ietf-detnet-dp-sol-mpls] for details on the mapping of IP flows to MPLS as well as general support for DetNet services using MPLS.
IP Edge Edge IP
End System Node Node End System
+---------+ +.........+ +.........+ +---------+
| Appl. |<---:Svc Proxy:-- E2E Service ---:Svc Proxy:-->| Appl. |
+---------+ +.........+ +.........+ +---------+
| IP |<---:IP : :Svc:----- IP flow ----:Svc: :IP :-->| IP |
+---------+ +---+ +---+ +---+ +---+ +---------+
|Transport| |Trp| |Trp| |Trp| |Trp| |Transport|
+-------.-+ +-.-+ +-.-+ +-.-+ +-.-+ +---.-----+
: Link : \ ,-----. / / ,-----. \
+........+ +-----[ Sub ]----+ +--[ Sub ]--+
[Network] [Network]
`-----' `-----'
|<--- IP --->| |<------ DetNet IP ------->| |<--- IP --->|
Figure 3: Non-DetNet aware IP end systems with IP DetNet Domain
Figure 3 illustrates another variant of Figure 1 where the end systems are not DetNet aware. In this case, edge nodes sit at the boundary of the DetNet domain and provide DetNet service proxies for the end applications by initiating and terminating DetNet service for the application's IP flows. The existing header information or an approach such as described in Section 4.7 can be used to support DetNet flow identification.
Non-DetNet and DetNet IP packets are identical on the wire. From data plane perspective, the only difference is that there is flow-associated DetNet information on each DetNet node that defines the flow related characteristics and required forwarding behavior. As shown above, edge nodes provide a Service Proxy function that "associates" one or more IP flows with the appropriate DetNet flow-specific information and ensures that the receives the proper traffic treatment within the domain.
Note: The operation of IEEE802.1 TSN end systems over DetNet enabled IP networks is not described in this document. While TSN flows could be encapsulated in IP packets by an IP End System or DetNet Edge Node in order to produce DetNet IP flows, the details of such are out of scope of this document.
This section provides informative considerations related to providing DetNet service to flows which are identified based on their header information. At a high level, the following are provided on a per flow basis:
Data-flows requiring DetNet service are generated and terminated on end systems. This document deals only with IP end systems. The protocols used by an IP end system are specific to an application and end systems peer with end systems using the same application encapsulation format. This said, DetNet's use of 6-tuple IP flow identification means that DetNet must be aware of not only the format of the IP header, but also of the next protocol carried within an IP packet.
When IP end systems are DetNet aware, no application-level or service-level proxy functions are needed inside the DetNet domain. For DetNet unaware IP end systems service-level proxy functions are needed inside the DetNet domain.
End systems need to ensure that DetNet service requirements are met when processing packets associated with a DetNet flow. When transporting packets, this means that packets are appropriately shaped on transmission and received appropriate traffic treatment on the connected sub-network, see Section 4.6 and Section 4.2.1 for more details. When receiving packets, this means that there are appropriate local node resources, e.g., buffers, to receive and process a DetNet flow packets.
As a general rule, DetNet IP domains need to be able to forward any DetNet flow identified by the IP 6-tuple. Doing otherwise would limit end system encapsulation format. From a practical standpoint this means that all nodes along the end-to-end path of a DetNet flows need to agree on what fields are used for flow identification, and the transport protocols (e.g., TCP/UDP/IPsec) which can be used to identify 6-tuple protocol ports.
From a connection type perspective two scenarios are identified:
L3 (IP) end systems may use any of these connection types. DetNet domain MUST allow communication between any end-systems using the same encapsulation format, independent of their connection type and DetNet capability. DN attached end systems have no knowledge about the DetNet domain and its encapsulation format. See Figure 4 for L3 end system connection scenarios.
____+----+
+----+ _____ / | ES3|
| ES1|____ / \__/ +----+___
+----+ \ / \
+ |
____ \ _/
+----+ __/ \ +__ DetNet domain /
| ES2|____/ L2/L3 |___/ \ __ __/
+----+ \_______/ \_______/ \___/
Figure 4: Connection types of L3 end systems
Within a DetNet domain, the DetNet enabled IP Routers interconnect links and sub-networks to support end-to-end delivery of DetNet flows. From a DetNet architecture perspective, these routers are DetNet relays, as they must be DetNet service aware. Such routers identify DetNet flows based on the IP 6-tuple, and ensure that the DetNet service required traffic treatment is provided both on the node and on any attached sub-network.
This solution provides DetNet functions end to end, but does so on a per link and sub-network basis. Congestion protection and latency control and the resource allocation (queuing, policing, shaping) are supported using the underlying link / sub net specific mechanisms. However, service protections (packet replication and packet elimination functions) are not provided at the DetNet layer end to end. But such service protection can be provided on a per underlying L2 link and sub-network basis.
+------+ +------+
| X | | X |
+======+ +------+
End-system | IP | | IP |
-----+------+-------+======+--- --+======+--
DetNet |L2/SbN| |L2/SbN|
+------+ +------+
Figure 5: Encapsulation of DetNet Routing in simplified IP service L3 end-systems
The DetNet Service Flow MUST be mapped to the link / sub-network specific resources using an underlying system specific means. This implies each DetNet aware node on path MUST look into the transported DetNet Service Flow packet and utilize e.g., a 5- (or 6-) tuple to find out the required mapping within a node.
As noted earlier, the Service Protection is done within each link / sub-network independently using the domain specific mechanisms (due the lack of a unified end to end sequencing information that would be available for intermediate nodes). Therefore, service protection (if any) cannot be provided end-to-end, only within sub-networks. This is shown for a three sub-network scenario in Figure 6, where each sub-network can provide service protection between its borders.
______
____ / \__
____ / \__/ \___ ______
+----+ __/ +====+ +==+ \ +----+
|src |__/ SubN1 ) | | \ SubN3 \____| dst|
+----+ \_______/ \ Sub-Network2 | \______/ +----+
\_ _/
\ __ __/
\_______/ \___/
+---+ +---------E--------+ +-----+
+----+ | | | | | | | +----+
|src |----R E--------R +---+ E------R E------+ dst|
+----+ | | | | | | | +----+
+---+ +-----R------------+ +-----+
Figure 6: Replication and elimination in sub-networks for DetNet IP networks
If end to end service protection is desired that can be implemented, for example, by the DetNet end systems using Layer-4 (L4) transport protocols or application protocols. However, these are out of scope of this document.
There are network scenarios, where the DetNet domain contains multiple technology segments (IEEE 802.1 TSN, MPLS) and all those segments are under the same administrative control (see Figure 7). Furthermore, DetNet nodes may be interconnected via TSN segments.
DetNet routers ensure that detnet service requirements are met per hop by allocating local resources, both receive and transmit, and by mapping the service requirements of each flow to appropriate sub-network mechanisms. Such mapping is sub-network technology specific. The mapping of IP DetNet Flows to MPLS is covered [I-D.ietf-detnet-dp-sol-mpls]. The mapping of IP DetNet Flows to IEEE 802.1 TSN is covered in Section 7.
______
_____ / \__
____ / \__/ \___ ______
+----+ __/ +======+ +==+ \ +----+
|src |__/ Seg1 ) | | \ Seg3 \__| dst|
+----+ \_______+ \ Segment-2 | \+_____/ +----+
\======+__ _+===/
\ __ __/
\_______/ \___/
Figure 7: DetNet domains and multiple technology segments
[Editor's note: This section is TBD. OAM may be dropped from this document and left for future study.]
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 existing network level 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).
CoS for DetNet flows carried in IPv6 is provided using the standard differentiated services code point (DSCP) field [RFC2474] and related mechanisms. The 2-bit explicit congestion notification (ECN) [RFC3168] field MAY also be used.
One additional consideration for DetNet nodes which support CoS services is that they MUST ensure that the CoS service classes do not impact the congestion protection and latency control mechanisms used to provide DetNet QoS. This requirement is similar to requirement for MPLS LSRs to that CoS LSPs do not impact the resources allocated to TE LSPs via [RFC3473].
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 (RSVP) (RSVP) and RSVP-TE [RFC3209] and [RFC3473]. The existing MPLS mechanisms defined to support CoS [RFC3270] can also be used to reserve resources for specific traffic classes.
In addition to explicit routes, and packet replication and elimination, DetNet provides zero congestion loss and bounded latency and jitter. As described in [I-D.ietf-detnet-architecture], there are different mechanisms that maybe used separately or in combination to deliver a zero congestion loss service. These mechanisms are provided by the either the MPLS or IP layers, and may be combined with the mechanisms defined by the underlying network layer such as 802.1TSN.
A baseline set of QoS capabilities for DetNet flows carried in PWs and MPLS can provided by MPLS with Traffic Engineering (MPLS-TE) [RFC3209] and [RFC3473]. TE LSPs can also support explicit routes (path pinning). Current service definitions for packet TE LSPs can be found in "Specification of the Controlled Load Quality of Service", [RFC2211], "Specification of Guaranteed Quality of Service", [RFC2212], and "Ethernet Traffic Parameters", [RFC6003]. Additional service definitions are expected in future documents to support the full range of DetNet services. In all cases, the existing label-based marking mechanisms defined for TE-LSPs and even E-LSPs are use to support the identification of flows requiring DetNet QoS.
QoS for DetNet service flows carried in IP MUST be provided locally by the DetNet-aware hosts and routers supporting DetNet flows. Such support will leverage the underlying network layer such as 802.1TSN. The traffic control mechanisms used to deliver QoS for IP encapsulated DetNet flows are expected to be defined in a future document. From an encapsulation perspective, the combination of the "6 tuple" i.e., the typical 5 tuple enhanced with the DSCP code, uniquely identifies a DetNet service flow.
Packets that are marked with a DetNet Class of Service value, but that have not been the subject of a completed reservation, can disrupt the QoS offered to properly reserved DetNet flows by using resources allocated to the reserved flows. Therefore, the network nodes of a DetNet network must:
The ability to aggregate individual flows, and their associated resource control, into a larger aggregate is an important technique for improving scaling of control in the data, management and control planes. This document identifies the traffic identification related aspects of aggregation of DetNet flows. The resource control and management aspects of aggregation (including the queuing/shaping/policing implications) will be covered in other documents. The data plane implications of aggregation are independent for PW/MPLS and IP encapsulated DetNet flows.
DetNet flows transported via IP have more limited aggregation options, due to the available traffic flow identification fields of the IP solution. One available approach is to manage the resources associated with a DSCP identified traffic class and to map (remark) individually controlled DetNet flows onto that traffic class. This approach also requires that nodes support aggregation ensure that traffic from aggregated LSPs are placed (shaped/policed/enqueued) in a fashion that ensures the required DetNet service is preserved.
In both the MPLS and IP cases, additional details of the traffic control capabilities needed at a DetNet-aware node may be covered in the new service descriptions mentioned above or in separate future documents. Management and control plane mechanisms will also need to ensure that the service required on the aggregate flow (H-LSP or DSCP) are provided, which may include the discarding or remarking mentioned in the previous sections.
While time synchronization can be important both from the perspective of operating the DetNet network itself and from the perspective of DetNet-based applications, time synchronization is outside the scope of this document. This said, a DetNet node can also support time synchronization or distribution mechanisms.
For example, [RFC8169] describes a method of recording the packet queuing time in an MPLS LSR on a packet by per packet basis and forwarding this information to the egress edge system. This allows compensation for any variable packet queuing delay to be applied at the packet receiver. Other mechanisms for IP networks are defined based on IEEE Standard 1588 [IEEE1588], such as ITU-T [G.8275.1] and [G.8275.2].
A more detailed discussion of time synchronization is outside the scope of this document.
[Editor's note: This section needs to be different for MPLS and IP solutions. Most solutions are technology dependent.]
While management plane and control plane are traditionally considered separately, from the Data Plane perspective there is no practical difference based on the origin of flow provisioning information. This document therefore does not distinguish between information provided by a control plane protocol, e.g., RSVP-TE [RFC3209] and [RFC3473], or by a network management mechanisms, e.g., RestConf [RFC8040] and YANG [RFC7950].
[Editor's note: This section is a work in progress. discuss here what kind of enhancements are needed for DetNet and specifically for PREOF and DetNet zero congest loss and latency control. Need to cover both traffic control (queuing) and connection control (control plane).]
[Editor's note: this is TBD.]
[Editor's note: this is TBD.]
[Editor's note: this is TBD.]
[Editor's note: this is TBD.]
[Editor's note: This is managed at the management plane or controller level.]
Some DetNet applications generate bidirectional traffic. While the DetNet data plane must support bidirectional DetNet flows, there are no special bidirectional features with respect to the data plane other than need for the two directions take the same paths. That is to say that bidirectional DetNet flows are solely represented at the management and control plane levels, without specific support or knowledge within the DetNet data plane. Fate sharing and associated vs co-routed bidirectional flows can be managed at the control level. Note, that there is no stated requirement for bidirectional DetNet flows to be supported using the same 6-tuple in each direction. Control mechanisms will need to support such bidirectional flows but such mechanisms are out of scope of this document. An example control plane solution for MPLS can be found in [RFC7551].
This section provides DetNet IP data plane procedures. These procedures have been divided into the following areas: flow identification, forwarding and traffic treatment. Flow identification includes those procedures related to matching IP and higher layer protocol header information to DetNet flow (state) information and service requirements. Flow identification is also sometimes called Traffic classification, for example see [RFC5777]. Forwarding includes those procedures related to next hop selection and delivery. Traffic treatment includes those procedures related to providing an identified flow with the required DetNet service.
DetNet IP data plane procedures also have implications on the control and management of DetNet flows and these are also covered in this section. Specifically this section identifies a number of information elements that will require support via the management and control interfaces supported by a DetNet node. The specific mechanism used for such support is out of the scope of this document. A summary of the management and control related information requirements is included. Conformance language is not used in the summary as it applies to future mechanisms such as those that may be provided in YANG models [YANG-REF-TBD].
IP and higher layer protocol header information is used to identify DetNet flows. All DetNet implementations that support this document MUST identify individual DetNet flows based on the set of information identified in this section. Note, that additional flow identification requirements, e.g., to support other higher layer protocols, may be defined in future.
The configuration and control information used to identify an individual DetNet flow MUST be ordered by an implementation. Implementations MUST support a fixed order when identifying flows, and MUST identify a DetNet flow by the first set of matching flow information.
Implementations of this document MUST support DetNet flow identification when the implementation is acting as a DetNet end systems, a relay node or as an edge node.
Implementations of this document MUST support DetNet flow identification based on IP header information. The IPv4 header is defined in [RFC0791] and the IPv6 is defined in [RFC8200].
Implementations of this document MUST support DetNet flow identification based on the Source Address field of an IP packet. Implementations SHOULD support longest prefix matching for this field, see [RFC1812] and [RFC7608]. Note that a prefix length of zero (0) effectively means that the field is ignored.
Implementations of this document MUST support DetNet flow identification based on the Destination Address field of an IP packet. Implementations SHOULD support longest prefix matching for this field, see [RFC1812] and [RFC7608]. Note that a prefix length of zero (0) effectively means that the field is ignored.
Note: using IP multicast destination address is also allowed.
Implementations of this document MUST support DetNet flow identification based on the IPv4 Protocol field when processing IPv4 packets, and the IPv6 Next Header Field when processing IPv6 packets. An implementation MUST support flow identification based based the next protocol values defined in Section 6.1.2. Other, non-zero values, SHOULD be used for flow identification. Implementations SHOULD allow for these fields to be ignored for a specific DetNet flow.
These fields are used to support Differentiated Services [RFC2474] and Explicit Congestion Notification [RFC3168]. Implementations of this document MUST support DetNet flow identification based on the IPv4 Type of Service field when processing IPv4 packets, and the IPv6 Traffic Class Field when processing IPv6 packets. Implementations MUST support bimask based matching, where one (1) values in the bitmask indicate which subset of the bits in the field are to be used in determining a match. Note that a zero (0) value as a bitmask effectively means that these fields are ignored.
[Authors note: the use of the IPv6 flow label is TBD this section requires discussion. Flow label based mapping requires src/dst adress mapping as well.]
Implementations of this document SHOULD support identification of DetNet flows based on the IPv6 Flow Label field. Implementations that support matching based on this field MUST allow for this fields to be ignored for a specific DetNet flow. When this fields is used to identify a specific DetNet flow, implementations MAY exclude the IPv6 Next Header field and next header information as part of DetNet flow identification.
Implementations of this document MUST support DetNet flow identification based on header information identified in this section. Support for TCP, UDP and IPsec flows are defined. Future documents are expected to define support for other protocols.
[Authors note: Other candidate protocols include IP in IP, GRE, DCCP - should and of these be required supported?]
DetNet flow identification for TCP [RFC0793] and UDP [RFC0768] is done based on the Source and Destination Port fields carried in each protocol's header. These fields share a common format and common DetNet flow identification procedures.
Implementations of this document MUST support DetNet flow identification based on the Source Port field of a TCP or UDP packet. Implementations MUST support flow identification based on a particular value carried in the field, i.e., an exact. Implementations SHOULD support range-based port matching. Implementation MUST also allow for the field to be ignored for a specific DetNet flow.
Implementations of this document MUST support DetNet flow identification based on the Destination Port field of a TCP or UDP packet. Implementations MUST support flow identification based on a particular value carried in the field, i.e., an exact. Implementations SHOULD support range-based port matching. Implementation MUST also allow for the field to be ignored for a specific DetNet flow.
IPsec Authentication Header (AH) [RFC4302] and Encapsulating Security Payload (ESP) [RFC4303] share a common format for the Security Parameters Index (SPI) field. Implementations MUST support flow identification based on a particular value carried in the field, i.e., an exact. Implementation SHOULD also allow for the field to be ignored for a specific DetNet flow.
The following summarizes the set of information that is needed to identify an individual DetNet flow:
Information identifying a DetNet flow is ordered and implementations use the first match. This can, for example, be used to provide a DetNet service for a specific UDP flow, with unique Source and Destination Port field values, while providing a different service for all other flows with that same UDP Destination Port value.
General requirements for IP nodes are defined in [RFC1122], [RFC1812] and [RFC6434], and are not modified by this document. The typical next-hop selection process is impacted by DetNet. Specifically, implementations of this document SHALL use management and control information to select the one or more outgoing interfaces and next hops to be used for a packet belonging to a DetNet flow.
The use of multiple paths or links, e.g., ECMP, to support a single DetNet flow will generally be avoided in order to meet DetNet service requirements.
The above implies that management and control functions will be defined to support this requirement, e.g., see [YANG-REF-TBD].
Implementations if this document MUST ensure that a DetNet flow receives the traffic treatment that is provisioned for it via management and control functions, e.g., via [YANG-REF-TBD]. General information on DetNet service can be found in [I-D.ietf-detnet-flow-information-model]. Typical mechanisms used to provide different treatment to different flows includes the allocation of system resources (such as queues and buffers) and provisioning or related parameters (such as shaping, and policing). Support can also be provided via an underlying network technology such as MPLS [I-D.ietf-detnet-dp-sol-mpls] and IEEE802.1 TSN Section 7. Other than in the TSN case, the specific mechanisms used by a DetNet node to ensure DetNet service delivery requirements are met for supported DetNet flows is outside the scope of this document.
The use of prefixes, wildcards, bimasks, and port ranges allows a DetNet node to aggregate DetNet flows. This aggregation can take place within a single node, when that node maintains state about both the aggregated and component flows. It can also take place between nodes, where one node maintains state about only flow aggregates while the other node maintains state on all or a portion of the component flows. In either case, the management or control function that provisions the aggregate flows must ensure that adequate resources are allocated and configured to provide combined service requirements of the component flows. As DetNet is concerned about latency and jitter, more than just bandwidth needs to be considered.
[Editor's note: This section is TBD - it covers how IP DetNet flows operate over an IEEE 802.1 TSN sub-network. BV to take a pass at filling in this section]
This section covers how IP DetNet flows operate over an IEEE 802.1 TSN sub-network. Figure 8 illustrates such a scenario, where two IP (DetNet) nodes are interconnected by a TSN sub-network. Node-1 is single homed and Node-2 is dual-homed. IP nodes can be (1) IP DetNet End System, (2) IP DetNet Edge or Relay node or (3) IP End System.
IP (DetNet) IP (DetNet)
Node-1 Node-2
........... ...........
<--: Service :-- DetNet flow ---: Service :-->
+---------+ +---------+
|Transport| |Transport|
+-------.-+ <-TSN Str-> +-.-----.-+
\ ,-------. / /
+----[ TSN-Sub ]---+ /
[ Network ]--------+
`-------'
<----------------- DetNet IP ---------------->
Figure 8: DetNet (DN) Enabled IP Network over a TSN sub-network
The Time-Sensitive Networking (TSN) Task Group of the IEEE 802.1 Working Group have defined (and are defining) a number of amendments to IEEE 802.1Q that provide zero congestion loss and bounded latency in bridged networks. Furthermore IEEE 802.1CB defines frame replication and elimination functions for reliability that should prove both compatible with and useful to, DetNet networks. All these functions have to identify flows those require TSN treatment.
As is the case for DetNet, a Layer 2 network node such as a bridge may need to identify the specific DetNet flow to which a packet belongs in order to provide the TSN/DetNet QoS for that packet. It also may need additional marking, such as the priority field of an IEEE Std 802.1Q VLAN tag, to give the packet proper service.
TSN capabilities of the TSN sub-network are made available for IP (DetNet) flows via the protocol interworking function defined in IEEE 802.1CB. For example, applied on the TSN edge port connected to the IP (DetNet) node it can convert an ingress unicast IP (DetNet) flow to use a specific multicast destination MAC address and VLAN, in order to direct the packet through a specific path inside the bridged network. A similar interworking pair at the other end of the TSN sub-network would restore the packet to its original destination MAC address and VLAN.
Placement of TSN functions depends on the TSN capabilities of nodes. IP (DetNet) Nodes may or may not support TSN functions. For a given TSN Stream (i.e., DetNet flow) an IP (DetNet) node is treated as a Talker or a Listener inside the TSN sub-network.
IP DetNet Flow and TSN Stream mapping is based on the active Stream Identification function, that operates at the frame level. IEEE 802.1CB defines an Active Destination MAC and VLAN Stream identification function, what can replace some Ethernet header fields namely (1) the destination MAC-address, (2) the VLAN-ID and (3) priority parameters with alternate values. Replacement is provided for the frame passed down the stack from the upper layers or up the stack from the lower layers.
Active Destination MAC and VLAN Stream identification can be used within a Talker to set flow identity or a Listener to recover the original addressing information. It can be used also in a TSN bridge that is providing translation as a proxy service for an End System. As a result IP (DetNet) flows can be mapped to use a particular {MAC-address, VLAN} pair to match the Stream in the TSN sub-network.
From the TSN sub-network perspective IP DetNet nodes without any TSN functions can be treated as TSN-unaware Talker or Listener. In such cases relay nodes in the TSN sub-network MUST modify the Ethernet encapsulation of the IP DetNet flow (e.g., MAC translation, VLAN-ID setting, Sequence number addition, etc.) to allow proper TSN specific handling of the flow inside the sub-network. This is illustrated in Figure 9.
IP (DetNet)
Node-1
<--------->
...........
<--: Service :-- DetNet flow ------------------
+---------+
|Transport|
+---------+ +---------------+
| L2 | | L2 Relay with |<--- TSN ----
| | | TSN function | Stream
+----.----+ +--.---------.--+
\__________/ \______
TSN-unaware
Talker / TSN-Bridge
Listener Relay
<-------- TSN sub-network -------
Figure 9: IP (DetNet) node without TSN functions
IP (DetNet) nodes being TSN-aware can be treated as a combination of a TSN-unaware Talker/Listener and a TSN-Relay, as shown in Figure 10. In such cases the IP (DetNet) node MUST provide the TSN sub-network specific Ethernet encapsulation over the link(s) towards the sub-network. An TSN-aware IP (DetNet) node MUST support the following TSN components:
[Editor's note: Should we added here requirements regarding IEEE 802.1Q C-VLAN component?]
IP (DetNet)
Node-2
<---------------------------------->
...........
<--: Service :-- DetNet flow ------------------
+---------+
|Transport|
+---------+ +---------------+
| L2 | | L2 Relay with |<--- TSN ---
| | | TSN function | Stream
+----.----+ +--.------.---.-+
\__________/ \ \______
\_________
TSN-unaware
Talker / TSN-Bridge
Listener Relay
<----- TSN Sub-network -----
<------ TSN-aware Tlk/Lstn ------->
Figure 10: IP (DetNet) node with TSN functions
A Stream identification component MUST be able to instantiate the following functions (1) Active Destination MAC and VLAN Stream identification function, (2) IP Stream identification function and (3) the related managed objects in Clause 9 of IEEE 802.1CB. IP Stream identification function provides a 6-tuple match.
The Sequence encode/decode function MUST support the Redundancy tag (R-TAG) format as per Clause 7.8 of IEEE 802.1CB.
TSN Streams supporting DetNet flows may use Frame Replication and Elimination for Redundancy (FRER) [802.1CB] based on the loss service requirements of the TSN Stream, which is derived from the DetNet service requirements of the DetNet mapped flow. The specific operation of FRER is not modified by the use of DetNet and follows IEEE 802.1CB.
FRER function and the provided service recovery is available only within the TSN sub-network (as shown in Figure 6) as the Stream-ID and the TSN sequence number are not valid outside the sub-network. An IP (DetNet) node represents a L3 border and as such it terminates all related information elements encoded in the L2 frames.
[Editor's note: This section is TBD - covers required behavior of DetNet node using a TSN underlay.]
[Editor's note: This section is TBD Covers Creation, mapping, removal of TSN Stream IDs, related parameters and,when needed, configuration of FRER. Supported by management/control plane.]
The security considerations of DetNet in general are discussed in [I-D.ietf-detnet-architecture] and [I-D.ietf-detnet-security]. Other security considerations will be added in a future version of this draft.
TBD.
RFC7322 limits the number of authors listed on the front page of a draft to a maximum of 5, far fewer than the 20 individuals below who made important contributions to this draft. The editor wishes to thank and acknowledge each of the following authors for contributing text to this draft. See also Section 11.
Loa Andersson Huawei Email: loa@pi.nu Yuanlong Jiang Huawei Email: jiangyuanlong@huawei.com Norman Finn Huawei 3101 Rio Way Spring Valley, CA 91977 USA Email: norman.finn@mail01.huawei.com Janos Farkas Ericsson Magyar Tudosok krt. 11 Budapest 1117 Hungary Email: janos.farkas@ericsson.com Carlos J. Bernardos Universidad Carlos III de Madrid Av. Universidad, 30 Leganes, Madrid 28911 Spain Email: cjbc@it.uc3m.es Tal Mizrahi Marvell 6 Hamada st. Yokneam Israel Email: talmi@marvell.com Lou Berger LabN Consulting, L.L.C. Email: lberger@labn.net
The author(s) ACK and NACK.
The following people were part of the DetNet Data Plane Solution Design Team:
The DetNet chairs serving during the DetNet Data Plane Solution Design Team:
Thanks for Stewart Bryant for his extensive review of the previous versions of the document.
[Editor's note: Add a simplified example of DetNet data plane and how labels etc work in the case of MPLS-based PSN and utilizing PREOF. The figure is subject to change depending on the further DT decisions on the label handling..]
TBD.