Networking Working Group L. Ginsberg, Ed.
Internet-Draft P. Psenak, Ed.
Intended status: Standards Track C. Filsfils
Expires: December 31, 2018 Cisco Systems
A. Bashandy
Individual
B. Decraene
Orange
Z. Hu
Huawei Technologies
June 29, 2018
IS-IS Extensions to Support Routing over IPv6 Dataplane
draft-bashandy-isis-srv6-extensions-03.txt
Abstract
Segment Routing (SR) allows for a flexible definition of end-to-end
paths by encoding paths as sequences of topological sub-paths, called
"segments". Segment routing architecture can be implemented over an
MPLS data plane as well as an IPv6 data plane. This draft describes
the IS-IS extensions required to support Segment Routing over an IPv6
data plane.
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.
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/.
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."
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This Internet-Draft will expire on December 31, 2018.
Copyright Notice
Copyright (c) 2018 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
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . . . 3
3. Advertising Maximum SRv6 SID Depths . . . . . . . . . . . . . 4
3.1. Maximum Segments Left MSD Type . . . . . . . . . . . . . 4
3.2. Maximum End Pop MSD Type . . . . . . . . . . . . . . . . 5
3.3. Maximum T.Insert MSD Type . . . . . . . . . . . . . . . . 5
3.4. Maximum T.Encaps MSD Type . . . . . . . . . . . . . . . . 5
3.5. Maximum End D MSD Type . . . . . . . . . . . . . . . . . 6
4. SRv6 SIDs and Reachability . . . . . . . . . . . . . . . . . 6
5. Advertising Locators and End SIDs . . . . . . . . . . . . . . 7
5.1. SRv6 Locator TLV Format . . . . . . . . . . . . . . . . . 7
5.2. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . . . 9
6. Advertising SRv6 End.X SIDs . . . . . . . . . . . . . . . . . 11
6.1. SRv6 End.X SID sub-TLV . . . . . . . . . . . . . . . . . 11
6.2. SRv6 LAN End.X SID sub-TLV . . . . . . . . . . . . . . . 13
7. Advertising Endpoint Function Types . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. SRv6 Locator TLV . . . . . . . . . . . . . . . . . . . . 15
8.1.1. SRv6 End SID sub-TLV . . . . . . . . . . . . . . . . 16
8.1.2. Revised sub-TLV table . . . . . . . . . . . . . . . . 16
8.2. SRv6 Capabilities sub-TLV . . . . . . . . . . . . . . . . 16
8.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs . . . . . 17
8.4. MSD Types . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Security Considerations . . . . . . . . . . . . . . . . . . . 18
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
With Segment Routing (SR) [I-D.ietf-spring-segment-routing], a node
steers a packet through an ordered list of instructions, called
segments.
Segments are identified through Segment Identifiers (SIDs).
Segment Routing can be directly instantiated on the IPv6 data plane
through the use of the Segment Routing Header defined in
[I-D.ietf-6man-segment-routing-header]. SRv6 refers to this SR
instantiation on the IPv6 dataplane.
The network programming paradigm
[I-D.filsfils-spring-srv6-network-programming] is central to SRv6.
It describes how any function can be bound to a SID and how any
network program can be expressed as a combination of SID's.
This document specifies IS-IS extensions that allow the IS-IS
protocol to encode some of these functions.
Familiarity with the network programming paradigm
[I-D.filsfils-spring-srv6-network-programming] is necessary to
understand the extensions specified in this document.
This document defines one new top level IS-IS TLV and several new IS-
IS sub-TLVs.
The SRv6 Capabilities sub-TLV announces the ability to support SRv6
and some Endpoint functions listed in Section 7 as well as
advertising limitations when applying such Endpoint functions.
The SRv6 Locator top level TLV announces SRv6 locators - a form of
summary address for the set of topology/algorithm specific SIDs
associated with a node.
The SRv6 End SID sub-TLV, the SRv6 End.X SID sub-TLV, and the SRv6
LAN End.X SID sub-TLV are used to advertise which SIDs are
instantiated at a node and what Endpoint function is bound to each
instantiated SID.
2. SRv6 Capabilities sub-TLV
A node indicates that it has support for SRv6 by advertising a new
SRv6- capabilities sub-TLV of the router capabilities TLV [RFC7981].
The SRv6 Capabilities sub-TLV may contain optional sub-sub-TLVs. No
sub-sub-TLVs are currently defined.
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The SRv6 Capabilities sub-TLV has the following format:
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 | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| optional sub-sub-TLVs...
Type: Suggested value 25, to be assigned by IANA
Length: 2 + length of sub-sub-TLVs
Flags: 2 octets The following flags are defined:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |O| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
O-flag: If set, the router supports use of the O-bit
in the Segment Routing Header(SRH) as defined in
[I-D.ali-spring-srv6-oam].
3. Advertising Maximum SRv6 SID Depths
[I-D.ietf-isis-segment-routing-msd] defines the means to advertise
node/link specific values for Maximum SID Depths (MSD) of various
types. Node MSDs are advertised in a sub-TLV of the Router
Capabilities TLV [RFC7981]. Link MSDs are advertised in a sub-TLV of
TLVs 22, 23, 141, 222, and 223.
This document defines the relevant SRv6 MSDs and requests MSD type
assignments in the MSD Types registry created by
[I-D.ietf-isis-segment-routing-msd].
3.1. Maximum Segments Left MSD Type
The Maximum Segments Left MSD Type specifies the maximum value of the
"SL" field [I-D.ietf-6man-segment-routing-header] in the SRH of a
received packet before applying the Endpoint function associated with
a SID.
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SRH Max SL Type: 41 (Suggested value - to be assigned by IANA)
If no value is advertised the supported value is assumed to be 0.
3.2. Maximum End Pop MSD Type
The Maximum End Pop MSD Type specifies the maximum number of SIDs in
the top SRH in an SRH stack to which the router can apply "PSP" or
USP" as defined in [I-D.filsfils-spring-srv6-network-programming]
flavors.
SRH Max End Pop Type: 42 (Suggested value - to be assigned by IANA)
If the advertised value is zero or no value is advertised
then it is assumed that the router cannot apply PSP or USP flavors.
3.3. Maximum T.Insert MSD Type
The Maximum T.Insert MSD Type specifies the maximum number of SIDs
that can be inserted as part of the "T.insert" behavior as defined in
[I-D.filsfils-spring-srv6-network-programming].
SRH Max T.insert Type: 43 (Suggested value - to be assigned by IANA)
If the advertised value is zero or no value is advertised
then the router is assumed not to support any variation
of the "T.insert" behavior.
3.4. Maximum T.Encaps MSD Type
The Maximum T.Encaps MSD Type specifies the maximum number of SIDs
that can be included as part of the "T.Encaps" behavior as defined in
[I-D.filsfils-spring-srv6-network-programming] .
SRH Max T.encaps Type: 44 (Suggested value - to be assigned by IANA)
If the advertised value is zero then the router can apply T.Encaps
only by encapsulating the incoming packet in another
IPv6 header without SRH the same way IPinIP encapsulation is
performed.
If the advertised value is non-zero then the router supports both
IPinIP and SRH encapsulation subject to the SID limitation
specified by the advertised value.
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3.5. Maximum End D MSD Type
The Maximum End D MSD Type specifies the maximum number of SIDs in an
SRH when performing decapsulation associated with "End.Dx" functions
(e.g., "End.DX6" and "End.DT6") as defined in
[I-D.filsfils-spring-srv6-network-programming].
SRH Max End D Type: 45 (Suggested value - to be assigned by IANA)
If the advertised value is zero or no value is advertised
then it is assumed that the router cannot apply
"End.DX6" or "End.DT6" functions if the extension
header right underneath the outer IPv6 header is an SRH.
4. SRv6 SIDs and Reachability
As discussed in [I-D.filsfils-spring-srv6-network-programming], an
SRv6 Segment Identifier (SID) is 128 bits and represented as
LOC:FUNCT
where LOC (the locator portion) is the L most significant bits and
FUNCT is the 128-L least significant bits. L is called the locator
length and is flexible. Each operator is free to use the locator
length it chooses.
A node is provisioned with topology/algorithm specific locators for
each of the topology/algorithm pairs supported by that node. Each
locator is a covering prefix for all SIDs provisioned on that node
which have the matching topology/algorithm.
Locators MUST be advertised in the SRv6 Locator TLV (see
Section 6.1). Forwarding entries for the locators advertised in the
SRv6 Locator TLV MUST be installed in the forwarding plane of
receiving SRv6 capable routers when the associated topology/algorithm
is supported by the receiving node.
Locators are routable and MAY also be advertised in Prefix
Reachability TLVs (236 or 237).
Locators associated with algorithm 0 (for all supported topologies)
SHOULD be advertised in a Prefix Reachability TLV (236 or 237) so
that legacy routers (i.e., routers which do NOT support SRv6) will
install a forwarding entry for algorithm 0 SRv6 traffic.
In cases where a locator advertisement is received in both in a
Prefix Reachability TLV and an SRv6 Locator TLV, the Prefix
Reachability advertisement MUST be preferred when installing entries
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in the forwarding plane. This is to prevent inconsistent forwarding
entries on SRv6 capable/SRv6 incapable routers.
SRv6 SIDs are advertised as sub-TLVs in the SRv6 Locator TLV except
for SRv6 End.X SIDs/LAN End.X SIDs which are associated with a
specific Neighbor/Link and are therefore advertised as sub-TLVs in
TLVs 22, 23, 222, 223, and 141.
SRv6 SIDs are not directly routable and MUST NOT be installed in the
forwarding plane. Reachability to SRv6 SIDs depends upon the
existence of a covering locator.
Adherence to the rules defined in this section will assure that SRv6
SIDs associated with a supported topology/algorithm pair will be
forwarded correctly, while SRv6 SIDs associated with an unsupported
topology/algorithm pair will be dropped. NOTE: The drop behavior
depends on the absence of a default/summary route covering a given
locator.
In order for forwarding to work correctly, the locator associated
with SRv6 SID advertisements MUST be the longest match prefix
installed in the forwarding plane for those SIDs. There are a number
of ways in which this requirement could be compromised
o Another locator associated with a different topology/algorithm is
the longest match
o A prefix advertisement (i.e., from TLV 236 or 237) is the longest
match
5. Advertising Locators and End SIDs
The SRv6 Locator TLV is introduced to advertise SRv6 Locators and End
SIDs associated with each locator.
This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236
and 237.
5.1. SRv6 Locator TLV Format
The SRv6 Locator TLV has the following format:
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 |R|R|R|R| MTID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Followed by one or more locator entries of the form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Loc Size | Locator (variable)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-tlv-len | Sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 27 (Suggested value to be assigned by IANA)
Length: variable.
MTID: Multitopology Identifier as defined in [RFC5120].
Note that the value 0 is legal.
Locator entry:
Metric: 4 octets. As described in [RFC5305].
Flags: 1 octet. The following flags are defined
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|D| Reserved |
+-+-+-+-+-+-+-+-+
where:
D bit: When the Locator is leaked from level-2 to level-1, the D
bit MUST be set. Otherwise, this bit MUST be clear. Locators
with the D bit set MUST NOT be leaked from level-1 to level-2.
This is to prevent looping.
The remaining bits are reserved for future use. They SHOULD be
set to zero on transmission and MUST be ignored on receipt.
Algorithm: 1 octet. Associated algorithm. Algorithm values
are defined in the IGP Algorithm Type registry.
Loc-Size: 1 octet. Number of bits in the Locator field.
(1 - 128)
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Locator: 1-16 octets. This field encodes the advertised SRv6
Locator. The Locator is encoded in the minimal number of
octets for the given number of bits.
Sub-TLV-length: 1 octet. Number of octets used by sub-TLVs
Optional sub-TLVs.
5.2. SRv6 End SID sub-TLV
The SRv6 End SID sub-TLV is introduced to advertise SRv6 Segment
Identifiers (SID) with Endpoint functions which do not require a
particular neighbor in order to be correctly applied
[I-D.filsfils-spring-srv6-network-programming]. SRv6 SIDs associated
with a neighbor are advertised using the sub-TLVs defined in
Section 6.
This new sub-TLV is advertised in the SRv6 Locator TLV defined in the
previous section. SRv6 End SIDs inherit the topology/algorithm from
the parent locator.
The SRv6 End SID sub-TLV has the following format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | SRv6 Endpoint Function |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 5 (Suggested value to be assigned by IANA)
Length: variable.
Flags: 1 octet. No flags are currently defined.
SRv6 Endpoint Function: 2 octets. As defined in
[I-D.filsfils-spring-srv6-network-programming]
Legal function values for this sub-TLV are defined in Section 7.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-TLVs
Optional sub-sub-TLVs
The SRv6 End SID MUST be a subnet of the associated Locator. SRv6
End SIDs which are NOT a subnet of the associated locator MUST be
ignored.
Multiple SRv6 End SIDs MAY be associated with the same locator. In
cases where the number of SRv6 End SID sub-TLVs exceeds the capacity
of a single TLV, multiple Locator TLVs for the same locator MAY be
advertised. For a given MTID/Locator the algorithm MUST be the same
in all TLVs. If this restriction is not met all TLVs for that MTID/
Locator MUST be ignored.
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6. Advertising SRv6 End.X SIDs
Certain SRv6 Endpoint functions
[I-D.filsfils-spring-srv6-network-programming] must be associated
with a particular neighbor, and in case of multiple layer 3 links to
the same neighbor, with a particular link in order to be correctly
applied.
This document defines two new sub-TLVs of TLV 22, 23, 222, 223, and
141 - namely "SRv6 End.X SID" and "SRv6 LAN End.X SID".
IS-IS Neighbor advertisements are topology specific - but not
algorithm specific. End.X SIDs therefore inherit the topology from
the associated neighbor advertisement, but the algorithm is specified
in the individual SID.
All End.X SIDs MUST be a subnet of a Locator with matching topology
and algorithm which is advertised by the same node in an SRv6 Locator
TLV. End.X SIDs which do not meet this requirement MUST be ignored.
6.1. SRv6 End.X SID sub-TLV
This sub-TLV is used to advertise an SRv6 SID associated with a point
to point adjacency. Multiple SRv6 End.X SID sub-TLVs MAY be
associated with the same adjacency.
The SRv6 End.X SID sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 Endpoint Function |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| Sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type: 43 (Suggested value to be assigned by IANA)
Length: variable.
Flags: 1 octet.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B|S|P|Reserved |
+-+-+-+-+-+-+-+-+
where:
B-Flag: Backup flag. If set, the End.X SID is eligible
for protection (e.g., using IPFRR) as described in [RFC8355].
S-Flag. Set flag. When set, the S-Flag indicates that the
End.X SID refers to a set of adjacencies (and therefore
MAY be assigned to other adjacencies as well).
P-Flag. Persistent flag. When set, the P-Flag indicates that
the End.X SID is persistently allocated, i.e., the
End.X SID value remains consistent across router restart
and/or interface flap.
Other bits: MUST be zero when originated and ignored when
received.
Algorithm: 1 octet. Associated algorithm. Algorithm values
are defined in the IGP Algorithm Type registry.
Weight: 1 octet. The value represents the weight of the
End.X SID for the purpose of load balancing. The use
of the weight is defined in [I-D.ietf-spring-segment-routing].
SRv6 Endpoint Function: 2 octets. As defined in
[I-D.filsfils-spring-srv6-network-programming]
Legal function values for this sub-TLV are defined in Section 7.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs
Note that multiple TLVs for the same neighbor may be required in
order to advertise all of the SRv6 End.X SIDs associated with that
neighbor.
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6.2. SRv6 LAN End.X SID sub-TLV
This sub-TLV is used to advertise an SRv6 SID associated with a LAN
adjacency. Since the parent TLV is advertising an adjacency to the
Designated Intermediate System(DIS) for the LAN, it is necessary to
include the System ID of the physical neighbor on the LAN with which
the SRv6 SID is associated. Given that a large number of neighbors
may exist on a given LAN a large number of SRv6 LAN END.X SID sub-
TLVs may be associated with the same LAN. Note that multiple TLVs
for the same DIS neighbor may be required in order to advertise all
of the SRv6 End.X SIDs associated with that neighbor.
The SRv6 LAN End.X SID sub-TLV has the following format:
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 | System ID (6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 Endpoint Function |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (128 bits) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (cont . . .) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sub-sub-tlv-len| sub-sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 44 (Suggested value to be assigned by IANA)
Length: variable.
System-ID: 6 octets of IS-IS System-ID of length "ID Length" as
defined in [ISO10589].
Flags: 1 octet.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B|S|P|Reserved |
+-+-+-+-+-+-+-+-+
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where B,S, and P flags are as described in Section 6.1.
Other bits: MUST be zero when originated and ignored when
received.
Algorithm: 1 octet. Associated algorithm. Algorithm values
are defined in the IGP Algorithm Type registry.
Weight: 1 octet. The value represents the weight of the
End.X SID for the purpose of load balancing. The use
of the weight is defined in [I-D.ietf-spring-segment-routing].
SRv6 Endpoint Function: 2 octets. As defined in
[I-D.filsfils-spring-srv6-network-programming]
Legal function values for this sub-TLV are defined in Section 7.
SID: 16 octets. This field encodes the advertised SRv6 SID.
Sub-sub-TLV-length: 1 octet. Number of octets used by sub-sub-
TLVs.
7. Advertising Endpoint Function Types
Endpoint function types are defined in
[I-D.filsfils-spring-srv6-network-programming]. The numerical values
are defined in the "SRv6 Endpoint Types" registry defined in
[I-D.filsfils-spring-srv6-network-programming]. This section lists
the Endpoint function types which MAY be advertised by IS-IS and the
SID sub-TLVs in which each type MAY appear.
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Endpoint | End | End.X | Lan End.X |
Function Type | SID | SID | SID |
----------------------|-------|-------|-----------|
End(no PSP, no USP) | Y | N | N |
----------------------|-------|-------|-----------|
End(with PSP) | Y | N | N |
----------------------|-------|-------|-----------|
End(with USP) | Y | N | N |
----------------------|-------|-------|-----------|
End(with PSP & USP) | Y | N | N |
----------------------|-------|-------|-----------|
End.T(no PSP, no USP) | Y | N | N |
----------------------|-------|-------|-----------|
End.T(with PSP) | Y | N | N |
----------------------|-------|-------|-----------|
End.T(with USP) | Y | N | N |
----------------------|-------|-------|-----------|
End.T(with PSP & USP) | Y | N | N |
----------------------|-------|-------|-----------|
End.X(no PSP, no USP) | N | Y | Y |
----------------------|-------|-------|-----------|
End.X(with PSP) | N | Y | Y |
----------------------|-------|-------|-----------|
End.X(with USP) | N | Y | Y |
----------------------|-------|-------|-----------|
End.X(with PSP & USP) | N | Y | Y |
----------------------|-------|-------|-----------|
End.DX6 | N | Y | Y |
----------------------|-------|-------|-----------|
End.DT6 | Y | N | N |
----------------------|-------|-------|-----------|
End.OTP | Y | N | N |
8. IANA Considerations
This document requests allocation for the following TLVs, sub- TLVs,
and sub-sub-TLVs as well updating the ISIS TLV registry and defining
a new registry.
8.1. SRv6 Locator TLV
This document adds one new TLV to the IS-IS TLV Codepoints registry.
Value: 27 (suggested - to be assigned by IANA)
Name: SRv6 Locator
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This TLV shares sub-TLV space with existing "Sub-TLVs for TLVs 135,
235, 236 and 237 registry". The name of this registry needs to be
changed to "Sub-TLVs for TLVs 27, 135, 235, 236 and 237 registry".
8.1.1. SRv6 End SID sub-TLV
This document adds the following new sub-TLV to the (renamed) "Sub-
TLVs for TLVs 27, 135, 235, 236 and 237 registry".
Value: 5 (suggested - to be assigned by IANA)
Name: SRv6 End SID
This document requests the creation of a new IANA managed registry
for sub-sub-TLVs of the SRv6 End SID sub-TLV. The registration
procedure is "Expert Review" as defined in [RFC7370]. Suggested
registry name is "sub-sub-TLVs for SRv6 End SID sub-TLV". No sub-
sub-TLVs are defined by this document except for the reserved value.
0: Reserved
1-255: Unassigned
8.1.2. Revised sub-TLV table
The revised table of sub-TLVs for the (renamed) "Sub-TLVs for TLVs
27, 135, 235, 236 and 237 registry" is shown below:
Type 27 135 235 236 237
1 n y y y y
2 n y y y y
3 n y y y y
4 y y y y y
5 y n n n n
11 y y y y y
12 y y y y y
8.2. SRv6 Capabilities sub-TLV
This document adds the definition of a new sub-TLV in the "Sub- TLVs
for TLV 242 registry".
Type: 25 (Suggested - to be assigned by IANA)
Description: SRv6 Capabilities
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This document requests the creation of a new IANA managed registry
for sub-sub-TLVs of the SRv6 Capability sub-TLV. The registration
procedure is "Expert Review" as defined in [RFC7370]. Suggested
registry name is "sub-sub-TLVs for SRv6 Capability sub-TLV". No sub-
sub-TLVs are defined by this document except for the reserved value.
0: Reserved
1-255: Unassigned
8.3. SRv6 End.X SID and SRv6 LAN End.X SID sub-TLVs
This document adds the definition of two new sub-TLVs in the "sub-
TLVs for TLV 22, 23, 25, 141, 222 and 223 registry".
Type: 43 (suggested - to be assigned by IANA)
Description: SRv6 End.X SID
Type: 44 (suggested - to be assigned by IANA)
Description: SRv6 LAN End.X SID
Type 22 23 25 141 222 223
43 y y y y y y
44 y y y y y y
8.4. MSD Types
This document defines the following new MSD types. These types are
to be defined in the IGP MSD Types registry defined in
[I-D.ietf-isis-segment-routing-msd] .
All values are suggested values to be assigned by IANA.
Type Description
------------------
41 SRH Max SL
42 SRH Max End Pop
43 SRH Max T.insert
44 SRH Max T.encaps
45 SRH Max End D
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9. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589], [RFC5304],
and [RFC5310].
10. Contributors
The following people gave a substantial contribution to the content
of this document and should be considered as co-authors:
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Stefano Previdi
Huawei Technologies
Email: stefano@previdi.net
Paul Wells
Cisco Systems
Saint Paul,
Minnesota
United States
Email: pauwells@cisco.com
Daniel Voyer
Email: daniel.voyer@bell.ca
Satoru Matsushima
Email: satoru.matsushima@g.softbank.co.jp
Bart Peirens
Email: bart.peirens@proximus.com
Hani Elmalky
Email: hani.elmalky@ericsson.com
Prem Jonnalagadda
Email: prem@barefootnetworks.com
Milad Sharif
Email: msharif@barefootnetworks.com>
Robert Hanzl
Cisco Systems
Millenium Plaza Building, V Celnici 10, Prague 1,
Prague, Czech Republic
Email rhanzl@cisco.com
Ketan Talaulikar
Cisco Systems, Inc.
Email: ketant@cisco.com
11. References
11.1. Normative References
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[I-D.ali-spring-srv6-oam]
Ali, Z., Filsfils, C., Kumar, N., Pignataro, C.,
faiqbal@cisco.com, f., Gandhi, R., Leddy, J., Matsushima,
S., Raszuk, R., Peirens, B., and G. Naik, "Operations,
Administration, and Maintenance (OAM) in Segment Routing
Networks with IPv6 Data plane (SRv6)", draft-ali-spring-
srv6-oam-00 (work in progress), February 2018.
[I-D.filsfils-spring-srv6-network-programming]
Filsfils, C., Li, Z., Leddy, J., daniel.voyer@bell.ca, d.,
daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P., and
M. Sharif, "SRv6 Network Programming", draft-filsfils-
spring-srv6-network-programming-04 (work in progress),
March 2018.
[]
Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-13 (work in
progress), May 2018.
[I-D.ietf-isis-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling MSD (Maximum SID Depth) using IS-IS", draft-
ietf-isis-segment-routing-msd-12 (work in progress), May
2018.
[ISO10589]
"Intermediate system to Intermediate system intra-domain
routeing information exchange protocol for use in
conjunction with the protocol for providing the
connectionless-mode Network Service (ISO 8473), ISO/IEC
10589:2002, Second Edition.", Nov 2002.
[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>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
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[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <https://www.rfc-editor.org/info/rfc5304>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <https://www.rfc-editor.org/info/rfc5310>.
[RFC7370] Ginsberg, L., "Updates to the IS-IS TLV Codepoints
Registry", RFC 7370, DOI 10.17487/RFC7370, September 2014,
<https://www.rfc-editor.org/info/rfc7370>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
[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>.
11.2. Informative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
[RFC8355] Filsfils, C., Ed., Previdi, S., Ed., Decraene, B., and R.
Shakir, "Resiliency Use Cases in Source Packet Routing in
Networking (SPRING) Networks", RFC 8355,
DOI 10.17487/RFC8355, March 2018,
<https://www.rfc-editor.org/info/rfc8355>.
Authors' Addresses
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Les Ginsberg (editor)
Cisco Systems
821 Alder Drive
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Peter Psenak (editor)
Cisco Systems
Pribinova Street 10
Bratislava 81109
Slovakia
Email: ppsenak@cisco.com
Clarence Filsfils
Cisco Systems
Brussels
Belgium
Email: cfilsfil@cisco.com
Ahmed Bashandy
Individual
Email: abashandy.ietf@gmail.com
Bruno Decraene
Orange
Issy-les-Moulineaux
France
Email: bruno.decraene@orange.com
Zhibo Hu
Huawei Technologies
Email: huzhibo@huawei.com
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