| Network Working Group | X. Geng |
| Internet-Draft | M. Chen |
| Intended status: Experimental | Huawei |
| Expires: January 5, 2020 | Y. Zhu |
| China Telecom | |
| July 04, 2019 |
DetNet SRv6 Data Plane Encapsulation
draft-geng-detnet-dp-sol-srv6-01
This document specifies Deterministic Networking data plane operation for SRv6 encapsulated user data.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
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Deterministic Networking (DetNet), as described in [I-D.ietf-detnet-architecture] provides a capability to carry specified data flows with extremely low data loss rates and bounded latency within a network domain. DetNet is enabled by a group of technologies, such as resource allocation, service protection and explicit routes.
Segment Routing(SR) leverages the source routing paradigm. An ingress node steers a packet through an ordered list of instructions, called "segments". SR can be applied over IPv6 data plane using the Segment Routing Extension Header (SRH,[I-D.ietf-6man-segment-routing-header]). A segment in segment routing terminology is not limited to a routing/forwarding function. A segment can be associated to an arbitrary processing of the packet in the node identified by the segment. In other words, an SRv6 Segment can indicate functions that are executed locally in the node where they are defined. SRv6 network Programming [I-D.filsfils-spring-srv6-network-programming] describe the different segments and functions associated to them.
This document describes how to implement DetNet in an SRv6 enabled domain, including :
• Source routing, which steers the DetNet flows through the network according to an explicit path with allocated resources;
• Network programming, which applies instructions (functions) to packets in some special nodes (or even all the nodes) along the path in order to guarantee, e.g., service protection and congestion protection.
DetNet SRv6 encapsulation and new SRv6 functions ([I-D.filsfils-spring-srv6-network-programming]) for DetNet are defined in this document. Control plane and OAM are not in the scope of this document.
Control plane and OAM are not in the scope of this document.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
Terminologies for DetNet go along with the definition in [I-D.ietf-detnet-architecture] and [RFC8402]. Other terminologies are defined as follows:
Conventions in the document are defined as follows:
The reverse encoding has been defined in order to optimise the processing time of the segment list. See [draft-ietf-6man-segment-routing-header] for more details.
[I-D.ietf-detnet-architecture]decomposes the DetNet data plane into two sub-layers: service sub-layer and transport sub-layer. Different from DetNet MPLS data plane solution, which uses DetNet Control Word(d-CW) and S-Label to support service sub-layer and uses T-Label to support transport sub-layer, no explicit sub-layer division exists in SRv6 data plane. A classical SRv6 DetNet data plane solution is showed in the picture below:
+-------------------+
| Outer Ipv6 Header |
+-------------------+
| SRH |
+-------------------+ +-------------------+
| Ipv6 Header | ----> | Ipv6 Header |
+-------------------+ +-------------------+
The outer IPv6 Header with the SRH is used for carrying DetNet flows. Traffic Engineering is instantiated in the segment list of SRH, and other functions and arguments for service protection (packet replication, elimination and ordering) and congestion control (packet queuing and forwarding) are also defined in the SRH.
| |
----IPv6--->|<---------------SRv6 DetNet------------->|<----IPv6---
| |
| +------+T2+----+ |
+---+ +---+ +-+-+ +-+-+ +---+ +---+
| E1+----| In|--+T1+--+R1 | |R2 |--+T4+--| Eg+----+ E2|
+---+ +---+ +-+-+ +-+-+ +---+ +---+
+-----+T3+-----+
The figure above shows that an IPv6 flow is sent out from the end station E1. The packet of the flow is encapsulated in an outer IPv6+SRH header as a DetNet SRv6 packet in the Ingress(In) and transported through an SRv6 DetNet domain. In the Egress(Eg), the outer IPv6 header+SRH of the packet is popped, and the packet is sent to the destination E2.
The figure above shows that an IPv6 flow is sent our from the end station: E1. The packet of the flow is encapsulated as a DetNet SRv6 packet in the Ingress(In) and transported through an SRv6 DetNet domain. In the Egress(Eg), the upper IPv6 header with SRH of the packet is popped, and the packet is transmitted to the destination(E2).
The DetNet packet processing is as follows:
Ingress:
Relay Node 1(Replication Node):
Relay Node 2(Elimination Node):
Egress:
The DetNet packet encapsulation is illustrated here below. It has to be noted that, in the example below, the R2 address is a SRH SID associated to a TBD function related to the packet replication the node R1 has to perform. The same (or reverse) apply to node R2 which is in charge of the discard of the duplicated packet. Here also a new function will have a new SID allocated to it and representing the delete of the duplication in R2.
To carry DetNet over SRv6, the following elements are required:
1. A method of identifying the SRv6 payload type;
2. A suitable explicit path to deliver the DetNet flow ;
3. A method of indicating packet processing, such as PREOF(Packet Replication, Elimination and Ordering as defined in [I-D.ietf-detnet-architecture]);
4. A method of identifying the DetNet flow;
5. A method of carrying DetNet sequence number;
6. A method of carrying queuing and forwarding indication to do congestion protection;
In this design, DetNet flows are encapsulated in an outer IPv6+SRH header at the Ingress Node. The SR policy identified in the SRH steers the DetNet flow along a selected path. The explicit path followed by a DetNet flow, which protect it from temporary interruptions caused by the convergence of routing, is encoded within the SID list of the SR policy. The network device inside the DetNet domain forwards the packet according to IPv6 Destination Address(DA), and the IPv6 DA is updated with the SID List according to SRv6 forwarding procedures defined in [I-D.ietf-6man-segment-routing-header] and [I-D.filsfils-spring-srv6-network-programming]
With SRv6 network programming, the SID list can also give instruments representing a function to be called at the node in the DetNet domain. Therefore DetNet specific functions defined in [I-D.ietf-detnet-architecture], corresponding to local packet processing in the network, can also be implemented by SRv6. New functions associated with SIDs for DetNet are defined in this document.
This document describes how DetNet flows are encapsulated/identified, and how functions of Packet Replication/Elimination/Ordering are implemented in an SRv6 domain. Congestion protection is also in the scope of this document.
Editor: This version only covers the functions of service protection and the congestion protection considerations will be added in the following versions.
This section defines options of SRv6 data plane solution to support DetNet Service Sub-layer.
An SRv6 Segment is a 128-bit value. SID is used as a shorter reference for "SRv6 Segment Identifier" or “SRV6 Segment”. SRv6 SID can also be represented as LOC:FUNCT, where:
The SRH for DetNet in the outer IPv6 header is showed as follows, according to [I-D.ietf-6man-segment-routing-header] and [I-D.filsfils-spring-srv6-network-programming]:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segment Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry | Flags | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Location & Function | | (Segment List[0] for relay node or edge node) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n] | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional TLVs | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The SRH specification allows the use of optional TLVs. Two new TLVs are defined to support DetNet service protection. DetNet Flow Identification TLV is used to uniquely identify a DetNet flow in an SRv6 DetNet node. DetNet sequence number is used to discriminate packets in the same DetNet flow. They are defined as follows:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESERVED | Flow Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |RESERVD| Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
New SRv6 Network Programming functions are defined as follows:
SRv6 SID can be represented as LOC:FUNCT:ARG::, where:
LOC, means "LOCATION" and defines the node associated with the SID (i.e.: represented by the SID).
FUNCT, means "FUNCTION", and identifies the processing that the node specified in LOC applies to the packet.
ARG, means "ARGUMENTS" and provides the additional arguments for the function. New SID functions for DetNet is defined in section 5.2.2. See [I-D.filsfils-spring-srv6-network-programming] for details on SRV6 Network Programming. The SRH for DetNet in the outer IPv6 header is illustrated as follows
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segment Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry | Flags | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Location & Function | | (Segment List[0] for relay node or edge node) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Location & Function | Flow Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Flow ID| Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n] | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional TLVS | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
New SID functions are defined as follows:
The function is similar as that has been defined in section 5.1.2.1. The only difference is that instead of retrieving the TLV values, this function retrieves the argument.
The function is similar as that has been defined in section 5.1.2.2. The only difference is that instead of retrieving the TLV values, this function retrieves the argument.
A non-forwarding DetNet SID is defined to carry Flow Identification and Sequence Number.
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Hdr Ext Len | Routing Type | Segment Left | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last Entry | Flags | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Location & Function | | (Segment List[0] for relay node or edge node) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment List[n] | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DetNet SID | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional TLVs | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TBD
TBD
TBD
TBD
Thank you for valuable comments from James Guichard and Andrew Mails.
| [I-D.filsfils-spring-srv6-network-programming] | Filsfils, C., Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d., Matsushima, S. and Z. Li, "SRv6 Network Programming", Internet-Draft draft-filsfils-spring-srv6-network-programming-07, February 2019. |
| [I-D.ietf-6man-segment-routing-header] | Filsfils, C., Dukes, D., Previdi, S., Leddy, J., Matsushima, S. and d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header (SRH)", Internet-Draft draft-ietf-6man-segment-routing-header-21, June 2019. |
| [I-D.ietf-detnet-architecture] | Finn, N., Thubert, P., Varga, B. and J. Farkas, "Deterministic Networking Architecture", Internet-Draft draft-ietf-detnet-architecture-13, May 2019. |
| [I-D.ietf-detnet-dp-sol-mpls] | Korhonen, J. and B. Varga, "DetNet MPLS Data Plane Encapsulation", Internet-Draft draft-ietf-detnet-dp-sol-mpls-02, March 2019. |
| [I-D.ietf-spring-segment-routing-policy] | Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., bogdanov@google.com, b. and P. Mattes, "Segment Routing Policy Architecture", Internet-Draft draft-ietf-spring-segment-routing-policy-03, May 2019. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC8402] | Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S. and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018. |