Internet DRAFT - draft-cl-spring-generalized-srv6-for-cmpr
draft-cl-spring-generalized-srv6-for-cmpr
SPRING Working Group W. Cheng
Internet-Draft China Mobile
Intended status: Standards Track Z. Li
Expires: 5 November 2023 C. Li
Huawei Technologies
F. Clad
Cisco Systems, Inc
A. Liu
ZTE Corporation
C. Xie
China Telecom
Y. Liu
China Mobile
S. Zadok
Broadcom
4 May 2023
Generalized SRv6 Network Programming for SRv6 Compression
draft-cl-spring-generalized-srv6-for-cmpr-07
Abstract
This document proposes Generalized Segment Routing over IPv6 (G-SRv6)
Networking Programming for SRv6 compression.
G-SRv6 can reduce the overhead of SRv6 by encoding the Generalized
SIDs(G-SID) in SID list, and it also supports to program SRv6 SIDs
and G-SIDs in a single SRH to support incremental deployment and
smooth upgrade.
G-SRv6 is fully compatible with SRv6 with no modification of SRH, no
new address consumption, no new route creation, and even no
modification of control plane.
G-SRv6 for Compression is designed based on the Compressed SRv6
Segment List Encoding in SRH [I-D.ietf-spring-srv6-srh-compression]
framework.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 November 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Concepts of G-SRv6 . . . . . . . . . . . . . . . . . . . . . 4
3.1. G-SID . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. G-SID Container . . . . . . . . . . . . . . . . . . . . . 5
3.3. G-SID Index . . . . . . . . . . . . . . . . . . . . . . . 6
3.4. COC Flavor . . . . . . . . . . . . . . . . . . . . . . . 6
4. G-SRH . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Packet Processing . . . . . . . . . . . . . . . . . . . . . . 9
6. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8. Running Code . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Interop-test Status . . . . . . . . . . . . . . . . . . . 13
8.2. Deployment Status . . . . . . . . . . . . . . . . . . . . 15
9. Protocol Extensions Requirements . . . . . . . . . . . . . . 15
9.1. Data Plane . . . . . . . . . . . . . . . . . . . . . . . 15
9.2. Control Plane . . . . . . . . . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. Security Considerations . . . . . . . . . . . . . . . . . . . 17
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
14.1. Normative References . . . . . . . . . . . . . . . . . . 17
14.2. Informative References . . . . . . . . . . . . . . . . . 18
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
Segment routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress
node by inserting an ordered list of instructions, called segments.
When segment routing is deployed on the IPv6 data plane, it is called
SRv6 [RFC8754]. For support of SR, a new routing header called
Segment Routing Header (SRH), which contains a list of SIDs and other
information, has been defined in [RFC8754]. In use cases like
Traffic Engineering, an ordered SID List with multiple SIDs is
inserted into the SRH to steer packets along an explicit path.
However, the size of SIDs (16 bytes per SID) in SRH proposes
challenges for packet processing and payload efficiency
[I-D.ietf-spring-compression-requirement]. In order to solve this
problem, this document proposes Generalized Segment Routing over IPv6
(G-SRv6) Networking Programming for SRv6 compression.
G-SRv6 supports to encode multiple types of Segments in an SRH,
called Generalized SRH (G-SRH). In SRv6 Compression, the G-SRH can
carry multiple SRv6 SID and G-SID(Generalized Segment Identifier)
containers in the SID list. A G-SID container may include an SRv6
SID or multiple G-SIDs and optional padding. A G-SID can be a
32-bits value of the original SRv6 SID, which contains the node ID
and function ID. By carrying G-SIDs instead of 128 bits SRv6 SID,
the problem of SRv6 header size can be solved, and the solution is
compatible with SRv6.
2. Terminology
This document makes use of the terms defined in [RFC8754], [RFC8402]
and [RFC8200], and the reader is assumed to be familiar with that
terminology. This document introduces the following terms:
Compressible SRv6 SID: It is the 128-bit SRv6 SID whose format can be
compressed. It is composed by Common Prefix and Generalized Segment
Identifier (G-SID) and optional arguments and padding.
Common Prefix: It is the same prefix shared by multiple SIDs.
G-SRv6: Generalized SRv6 Network Programming
G-SRH: Generalized Segment Routing Header. It keeps the same format
and code point with original SRH, which can carry multiple G-SIDs and
original SIDs.
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G-SID: Generalized Segment Identifier.It is a Compressed SID(C-SID)
[I-D.ietf-spring-srv6-srh-compression].
G-SID Container: Generalized Segment Identifier Container.It is a
C-SID container [I-D.ietf-spring-srv6-srh-compression].
2.1. Requirements Language
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.
3. Concepts of G-SRv6
This section describes the concepts of G-SRv6.
3.1. G-SID
In an SRv6 domain, the SIDs are allocated from an address block,
called SID space. Therefore, the SIDs allocated from the same SID
space share the common prefix. Also, if the length of the SID is
less than 128 bits, then padding is required. In an SID List, the
common prefix and padding are redundant. Reducing the redundant
information can reduce the overhead of SRv6.
This document defines a Generalized SID (G-SID) to carry the
different part of the original SRv6 SID in the SRH to reduce the size
of the SRH. The G-SID can be a 32-bits value following the common
prefix in the original SRv6 SID. An SRv6 SID with this format is
called compressible SRv6 SID. The format of a compressible SRv6 SID
with 32-bits G-SID is shown in Figure 1.
0 Variable Length 32 bits 128 bits
+--------------------------------------------------------------+
| Common Prefix | G-SID | Args/padding |
+--------------------------------------------------------------+
|<-------- Locator ----------------->|
Figure 1. 32 bits G-SID in SRv6 SID
In order to indicate the format of the SRv6 SID is compressible,
control plane extension may be considered. This is out of scope of
this document, and can be described in other documents.
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3.2. G-SID Container
In order to align with 128 bits, a 128 bit G-SID Container is
defined. A G-SID Container is a 128 bits value, and it may contain
different type of SIDs:
* an SRv6 SID: A G-SID Container contains a single SRv6 SID.
* A Micro SID Carrier: A G-SID Container contains a Micro SID
carrier [I-D.filsfils-spring-net-pgm-extension-srv6-usid].
* Multiple G-SIDs: A G-SID Container contains multiple G-SIDs and
optional padding. When G-SID is a 32-bits value, a G-SID
Container can consist of 4 G-SIDs. If the length of G-SIDs in a
G-SID Container is less than 128 bits, then padding is required.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(a)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(b)
Figure 2. G-SID Container for Compression
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3.3. G-SID Index
In order to locate the G-SID within the G-SID Container, this section
defines Generalized SID Index (SI) to indicate the location of the
G-SID within the current G-SID Container.
SI is a location argument of the G-SID, which is the least bits in
the argument part. When G-SID is a 32 bits value, the SI is the
least 2 bits in Argument.
0 Variable Length 32 bits 128 bits
+--------------------------------------------------------------+
| Common Prefix | G-SID |SI| Padding |
+--------------------------------------------------------------+
Figure 4. SI in the IPv6 DA
3.4. COC Flavor
In order to indicate the SRv6 compression processing, updating the
next 32-bits G-SID to the IPv6 DA, this section defines COC(Continue
of Compression) Flavor.
When a node receives an SID with COC Flavor, it indicates to update
the G-SID part in IPv6 DA with the next 32 bits G-SID.
When a node receives an SID without COC Flavor, the node processes
the packet as a normal SRv6 packet [RFC8986], for example, update the
IPv6 DA with the next 128 bits SID if SL >0.
Therefore, if the behavior of the last G-SID in the G-SID list has no
COC Flavor, then the next 128 bits SID will be updated to the DA, so
it indicates the end of the compression sub-path.
When COC Flavor applies to END, END.X and END.T, the SIDs can be
advertised via the IS-IS [I-D.ietf-lsr-isis-srv6-extensions], and the
SRv6 SID Structure Sub-Sub-TLV MUST be carried to indicate the format
of the SRv6 SID. The Locator.Block length indicates the length of
the common prefix, and the G-SID is the following 32-bits value after
the Block, which contains the Node ID and Function ID.
4. G-SRH
G-SRH supports to encode different types of segment in a single SRH
without modifying the encapsulation format of SRH.
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When an SRv6 path travels normal SRv6 nodes and compressed SRv6
nodes, the SRv6 SID and G-SIDs can be encoded in a single G-SRH.
For easier understanding, this document assumes that the Compressible
SRv6 SID consists of 64 bits common prefix and 32 bits G-SID. The
encoding can be shown as follows.
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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 | Segments Left|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flag | Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Other G-SID Container |
. ... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| Optional Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 0 | G-SID Container 0
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ... . ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| G-SID 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 2 | G-SID Container j
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| G-SID 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| Common Prefix |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G-SID Container k
| G-SID 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Generalized Segment List[n] (128 bits SRv6 SID) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional Type Length Value objects (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. G-SRH for SRv6 Compression
Where:
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* Common Prefix: the common prefix shared by the Compressible SRv6
SIDs in the current compression sub-path. Usually, it is the
prefix of the SID space, called Locator Block in control plane
[RFC8986]. Operators are free to configure the length and the
value of the common prefix based on the address planning of their
networking.
* G-SID: 32-bits Generalized SID.
* Padding: Must be zero. When the length of G-SIDs within the G-SID
Container is less than 128 bits, then padding is needed.
5. Packet Processing
This section describes the pseudo code of COC Flavor, and it replaces
the S13 and S14 of End, End.X, and End.T's pseudo code [RFC8986].
The pseudo code is shown below.
When N receives a packet whose IPv6 DA is S and S is a local SID with
COC Flavor, N does:
1. If (DA.SI != 0) { //ref1
2. Decrement DA.SI by 1.
3. } Else {
4. Decrement Segments Left by 1.
5. Set DA.SI to 3 in the IPv6 Destination Address
6. }
7. Copy Segment List[Segments Left][DA.SI] into the bits //ref2
[B..B+31] of the IPv6 Destination Address.
* Ref1: an SID with COC flavor indicates the SRv6 compression
processing that the node needs to update the next 32 bits G-SID to
the IPv6 DA.
- When the SI is greater than 0, the next G-SID is the next G-SID
in the current G-SID Container.
- Otherwise, the next G-SID is the first G-SID in the next G-SID
Container.
* Ref2: B is the length of the Locator Block [RFC8986].
An SID without COC Flavor will be processed following the SRv6
processing. The node will update the next 128 bit SID to the IPv6 DA
if the SL > 0.
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6. Illustration
This section describes a simple example of G-SRv6 for compression.
The reference topology is shown below.
*--------------------*
* SRv6 Domain *
* *
Tenant10 CE1--0-1-2-3-4-5-6-7-8-9-10--CE2 Tenant10
* *
*--------------------*
Figure 5. Reference topology
Nodes 0 - 10 are G-SRv6 enabled nodes within the SRv6 domain, and
node 0 is the ingress node of the G-SRv6 path while the node 10 is
the egress node.
Nodes CE1 and CE2 are tenants of VPN 10, and they are outside of the
SRv6 domain.
In order to ease the reading of the example, this section introduces
a simplified SID allocation schema.
* 2001:db8::/64 is dedicated to the internal SRv6 SID space, which
is the common prefix for the SIDs as well.
* Node k has 2001:db8:0:0:k::/80 for its local SID space. Its SIDs
will be explicitly allocated from that block.
* 2001:db8:0:0:k:1:: represents the End.X SID with COC allocated by
node K, and it is associated with interface N of node K. For
instance, 2001:db8:0:0:1:1:: represents the End.X with COC flavor
allocated by node 1.
* 2001:db8:0:0:k:2:: represents the End.X SID without COC allocated
by node K, and it is associated with interface N of node K. For
instance, 2001:db8:0:0:1:2:: represents the End.X without COC
flavor allocated by node 1.
* 2001:db8:0:0:10:10:: is an END.DT4 SID initiated by node 10, which
is associated with the VRF10.
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Therefore, the SID 2001:db8:0:0:1:1::, 2001:db8:0:0:2:1::,
2001:db8:0:0:3:1::, 2001:db8:0:0:4:1::, 2001:db8:0:0:5:1::,
2001:db8:0:0:6:1::, 2001:db8:0:0:7:1::, 2001:db8:0:0:8:1:: are SRv6
End.X SIDs with COC Flavor, and 2001:db8:0:0:9:2:: is a Compressible
SRv6 End.X SID.
The SID list [2001:db8:0:0:1:1::, 2001:db8:0:0:2:1::,
2001:db8:0:0:3:1::, 2001:db8:0:0:4:1::, 2001:db8:0:0:5:1::,
2001:db8:0:0:6:1::, 2001:db8:0:0:7:1::, 2001:db8:0:0:8:1::,
2001:db8:0:0:9:2::, 2001:db8:0:0:10:10::] is calculated for a strict
TE path from Node 1 to Node 10 for the VPN traffic of tenant 10.
In G-SRv6, the SID list can be encoded as [2:1, 3:1, 4:1, 5:1, 6:1,
7:1, 8:1, 9:2, 2001:db8:0:0:10:10::] in reduced mode. The G-SID
Container encoding is shown below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| |
| 2001:db8:0:0:10:10:: | G-SID Container 0
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| 9:2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 8:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G-SID Container 1
| 7:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 6:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
| 5:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ G-SID Container 2
| 3:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 2:1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ----
Figure 6. G-SID Container Encoding for G-SRv6
The packets forwarding procedures:
* Node 0 sends the SRv6 packet with G-SRH to the node 1.The SL is 3.
The Active SID in IPv6 DA is 2001:db8:0:0:1:1::.
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* When node 1 receives the packet, the IPv6 DA is
2001:db8:0:0:1:1::, which is a Local End.X with COC Flavor SID.
The SRH.SL is 3, and DA.SI is 0. The node processes the packet:
SL = SL-1,DA.SI =3, pointing to the next G-SID 2:1, and updates
SRH[SL=2][DA.SI=3] to the IPv6 DA[CP:CP+31], where CP is the
length of the common prefix. The packet is forwarded with the new
IPv6 DA 2001:db8:0:0:2:1:C::, to the node 2.
* When node 2 receives the packet, the IPv6 DA is
2001:db8:0:0:2:1:C::, which is a Local End.X with COC Flavor SID.
The SRH.SL is 2, and DA.SI is 3. The node processes the packet:
DA.SI --, pointing to the next G-SID 3:1, and updates
SRH[SL=2][DA.SI=2] to the IPv6 DA[CP:CP+31]. The packet is
forwarded with the new IPv6 DA 2001:db8:0:0:3:1:8::, to the node
3.
* Similar to node 1 and 2, the node 3,4,5,6,7,8 process the packet
and forward with the new IPv6 DA.
* When node 9 receives the packet, the IPv6 DA is
2001:db8:0:0:9:2::, which is a Local End.X SID. The SRH.SL is 1.
The node updates the next SID 2001:db8:0:0:10:10:: to the IPv6 DA
and forwards the packet to the node 10.
* Node 10 receives the packet, and the IPv6 DA is an VPN SID
allocated by itself, the node processes the SRv6 VPN SID.
This illustration shows that 70 % overhead of SID list is removed in
G-SRv6(10 x 16 Bytes to 3 x 16 Bytes), also, it shows the
capabilities of encoding G-SIDs and SRv6 SIDs in a single G-SRH.
7. Benefits
* G-SRv6 is fully compatible with SRv6
- No SRH encapsulation modification.
- No new address consumption: Compressible SRv6 SIDs can be
allocated from the Locator allocated to the node.
- No new route advertisements: Compressible SRv6 SIDs can share
the same locator with the normal SRv6 SID.
- No security policy modification: when reusing the Locator with
SRv6 SIDs, no security policy need to be updated.
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- No control plane modification: Controller can install the SR
policy with 128-bits G-SID Containers, and the ingress treats
the G-SID Container as an opaque 128-bits SID without
understanding the structure of it. G-SRv6 capable nodes
understand the COC flavor behaviors, while Compression disable
SRv6 nodes are unaware of Compression.
* G-SRv6 reduces the SRv6 encapsulation size.
- 128 bits to 32 bits, up to 75 % overhead is reduced. More
overhead is reduced when the G-SID is a 16-bits value.
* G-SRv6 has efficient address consumption and easy to deploy
- Operators are free to allocate an SID space from their address
space.
- No affect of networking(i.e. routes and ACL security policies)
by using the existing Locator to allocate compressible SRv6
SIDs.
* G-SRv6 is hardware friendly
- Same SRv6 processing flow with a new IPv6 DA update method
- Leverages the mature hardware capabilities (DA update, DA
longest match)
- Avoids extra lookup in indexed mapping table
* G-SRv6 supports incremental deployments, which can be deployed on
demand.
8. Running Code
8.1. Interop-test Status
The G-SRv6 mechanism has been implemented on the following 10+
hardware devices, software implementations and SDN controllers.
They had also successfully participated in the series of joint
interoperability testing events hosted by China Mobile from June 2020
to November 2020.
The following hardware devices and software implementations had
successfully passed the series of G-SRv6 dataplane interoperability
testing (in alphabetical order).
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* Chipsets
- Broadcom Jericho 2 BCM88690
- Centec CTC7132
- Intel Barefoot Tofino BFN-T10
- Marvell Falcon 98CX8580
* Devices
- Cisco ASR 9000
- Cisco IOS XRv9000
- Huawei NE40E
- Huawei NE5000E
- H3C CR16010H-FA
- H3C CR19000-8
- Ruijie F9300 Switch
- ZTE M6000-8S Plus
- ZTE M6000-3S
* Test Equipment
- IXIA XGS12
- Spirent TestCenter N4U
The following hardware devices and software implementations had
successfully passed the series of G-SRv6 with control plane
interoperability test (in alphabetical order).
* China Unitechs Unified Controller
* Huawei NE40E and NE5000E
* H3C CR16010H-FA and CR19000-8
* Spirent TestCenter N4U
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* ZTE M6000-8S Plus and M6000-3S
Regarding open-source implementations, G-SRv6 has been implemented on
Linux Kernel.
8.2. Deployment Status
In addition, China Mobile had come up with China Unitechs, Huawei,
ZTE and H3C to successfully deploy trial of G-SRv6 (with control
plane) in their three province branch networks in November 2020,
respectively.
The details are listed below (in alphabetical order).
* Huawei devices with a China Unitechs Unified Controller, Guangdong
Province. L3VPN over G-SRv6 BGP TE policy.
* H3C devices with a China Unitechs Unified Controller, Zhejiang
Province. L3VPN over G-SRv6 BGP TE policy.
* ZTE devices with a China Unitechs Unified Controller, Henan
Province. L3VPN over G-SRv6 BGP TE policy.
More information of G-SRv6 interop-test and deployment status will be
updated as the work progresses.
9. Protocol Extensions Requirements
This section describes the protocol extension requirements.
9.1. Data Plane
REQ1-01: An SRv6 compression path can be represented as a G-SID
Container list consists of a compressible SRv6 SID and G-SID
Containers.
REQ1-02: A G-SID Container consists of at most 4 (32-bits) G-SIDs, if
the number of G-SID is less than 4, then padding is required to align
with 128 bits.
REQ1-03: If the first Compressible SRv6 SID is copied to the IPv6 DA,
then following G-SIDs should be updated to the IPv6 DA by the nodes
along the SRv6 compression sub-path accordingly.
REQ1-04: The last G-SID in the G-SID Container for the SRv6
compression sub-path is the a G-SID without COC flavor.
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REQ1-05: When process the G-SID with COC flavor in the IPv6 DA, the
next G-SID is updated to the IPv6 DA.
9.2. Control Plane
REQ1-11: ISIS/OSPF/BGP-LS/PCEP extensions for advertising the
capabilities of supporting G-SRv6 for SRv6 compression.
REQ1-12: ISIS/OSPF/BGP-LS/BGP extensions for advertising Compressible
SRv6 SIDs.
REQ1-13: ISIS/OSPF/BGP-LS/BGP extensions for advertising the
Continue-of-compression(COC) flavor SID.
REQ1-21: BGP SR Policy extensions for programming a G-SRv6 path
combining with Compressible SRv6 SIDs and SRv6 SIDs.
REQ1-31: PCEP SR Policy extensions for programming a G-SRv6 path
combining with G-SIDs and SRv6 SIDs.
REQ1-32: PCEP extensions for programming a G-SRv6 path combining with
G-SIDs and SRv6 SIDs.
10. IANA Considerations
This document requests IANA to allocate the following codepoints for
COC flavor behaviors within the "SRv6 Endpoint Behaviors" sub-
registry under the top-level "Segment Routing Parameters" registry.
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+-------+--------+----------------------------+-----------+
| Value | Hex | Endpoint behavior | Reference |
+-------+--------+----------------------------+-----------+
| 101 | 0x0065 | End with COC | [This.ID] |
| 102 | 0x0066 | End with PSP&COC | [This.ID] |
| 104 | 0x0068 | End with PSP&USP&COC | [This.ID] |
| 105 | 0x0069 | End.X with COC | [This.ID] |
| 106 | 0x006A | End.X with PSP&COC | [This.ID] |
| 108 | 0x006C | End.X with PSP&USP&COC | [This.ID] |
| 109 | 0x006D | End.T with COC | [This.ID] |
| 110 | 0x006E | End.T with PSP&COC | [This.ID] |
| 112 | 0x0070 | End.T with PSP&USP&COC | [This.ID] |
| 130 | 0x0082 | End with PSP&USD&COC | [This.ID] |
| 131 | 0x0083 | End with PSP&USP&USD&COC | [This.ID] |
| 133 | 0x0085 | End.X with PSP&USD&COC | [This.ID] |
| 135 | 0x0087 | End.X with PSP&USP&USD&COC | [This.ID] |
| 137 | 0x0089 | End.T with PSP&USD&COC | [This.ID] |
| 139 | 0x008B | End.T with PSP&USP&USD&COC | [This.ID] |
+-------+--------+----------------------------+-----------+
Table 1: IETF - SRv6 Endpoint Behaviors
11. Security Considerations
The security considerations described in [RFC8754], and [RFC8402] are
applicable to this specification. No additional security measure is
required.
12. Contributors
TBD
13. Acknowledgements
TBD
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[I-D.ietf-spring-srv6-srh-compression]
Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, "Compressed SRv6 Segment List Encoding in SRH", Work
in Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
compression-04, 31 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
srv6-srh-compression-04>.
14.2. Informative References
[I-D.filsfils-spring-net-pgm-extension-srv6-usid]
Filsfils, C., Camarillo, P., Cai, D., Voyer, D., Meilik,
I., Patel, K., Henderickx, W., Jonnalagadda, P., Melman,
D. T., Liu, Y., and J. Guichard, "Network Programming
extension: SRv6 uSID instruction", Work in Progress,
Internet-Draft, draft-filsfils-spring-net-pgm-extension-
srv6-usid-14, 12 December 2022,
<https://datatracker.ietf.org/doc/html/draft-filsfils-
spring-net-pgm-extension-srv6-usid-14>.
[I-D.ietf-spring-compression-requirement]
Cheng, W., Xie, C., Bonica, R., Dukes, D., Li, C., Peng,
S., and W. Henderickx, "Compressed SRv6 SID List
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Requirements", Work in Progress, Internet-Draft, draft-
ietf-spring-compression-requirement-03, 3 April 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-spring-
compression-requirement-03>.
[I-D.ietf-lsr-isis-srv6-extensions]
Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
Z. Hu, "IS-IS Extensions to Support Segment Routing over
IPv6 Dataplane", Work in Progress, Internet-Draft, draft-
ietf-lsr-isis-srv6-extensions-19, 14 November 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
isis-srv6-extensions-19>.
Authors' Addresses
Weiqiang Cheng (editor)
China Mobile
No.32 Xuanwumen west street
Beijing
100053
China
Email: chengweiqiang@chinamobile.com
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
Email: lizhenbin@huawei.com
Cheng Li (editor)
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
Email: c.l@huawei.com
Francois Clad
Cisco Systems, Inc
France
Email: fclad@cisco.com
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Aihua Liu
ZTE Corporation
Shenzhen
China
Email: liu.aihua@zte.com.cn
Chongfeng Xie
China Telecom
Technology Innovation park, Changping District
Beijing
China
Email: xiechf@chinatelecom.cn
Yisong Liu
China Mobile
No.32 Xuanwumen west street
Beijing
Email: liuyisong@chinamobile.com
Shay Zadok
Broadcom
Israel
Email: shay.zadok@broadcom.com
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