Internet Engineering Task Force J. Harrison
INTERNET-DRAFT J. Berger
Expires July 2005 M. Bartlett
Data Connection Ltd (DCL)
January 2005
IPv6 Traffic Engineering in IS-IS
<draft-ietf-isis-ipv6-te-00.txt>
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Copyright Notice
Copyright (C) The Internet Society 2005. All Rights Reserved.
Abstract
This document specifies a method for exchanging IPv6 Traffic
Engineering information using the IS-IS routing protocol. The
described method uses three new TLVs, together with two new sub-TLVs
of the Extended IS Reachability TLV. The information distributed
allows a CSPF algorithm to calculate traffic engineered routes using
IPv6 addresses.
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1. Terms
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.
2. Overview
[TE] and [GMPLS] define a number of TLVs and sub-TLVs that allow
Traffic Engineering information to be disseminated by the IS-IS
protocol [IS-IS]. The addressing information passed in these TLVs is
IPv4 specific.
[IPv6] describes how the IS-IS protocol can be used to carry out SPF
routing for IPv6. It does this by defining IPv6 specific TLVs that
are analogous to the TLVs used by IS-IS for carrying IPv4 addressing
information.
MPLS Traffic Engineering is very successful and, as the use of IPv6
grows, there is a need to be able to support Traffic Engineering in
IPv6 networks.
This document defines the TLVs that allow Traffic Engineering
(including GMPLS TE) information to be carried in IPv6 IS-IS
networks.
3. Summary of operation
3.1 Identifying IS-IS links using IPv6 addresses
Each IS-IS link has certain properties - bandwidth, shared risk
link groups (SRLGs), switching capabilities and so on. The IS-IS
extensions defined in [TE] and [GMPLS] describe how to associate
these traffic engineering parameters with IS-IS links. These TLVs
use IPv4 addresses to identify the link (or local/remote link
identifiers on unnumbered links).
When IPv6 is used, a numbered link may be identified by IPv4 and/or
IPv6 interface addresses. The type of identifier used does not
affect the properties of the link - it still has the same bandwidth,
SRLGs, switching capabilities.
This document describes an approach for supporting IPv6 traffic
engineering, by defining TLV extensions that allow TE links and nodes
to be identified by IPv6 addresses.
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3.1.1 IPv6 address types
An IPv6 address can have global, site-local or link-local scope.
- A link-local IPv6 address is valid only within the scope of a
single link, and may only be referenced on that link.
- A site-local IPv6 address is valid in the scope of a single
Autonomous System (AS).
- A global IPv6 address is valid within the scope of the Internet.
Because the IPv6 traffic engineering TLVs present in LSPs are
propagated across networks, they MUST NOT use link-local addresses.
As IS-IS only operates within the scope of a single AS, IS-IS does
not need to differentiate between global and site-local addresses.
3.2 IP addresses used in Traffic Engineering TLVs
This section lists the IP addresses used in the TLVs defined in
[TE] and [GMPLS], and gives an overview of the required IPv6
equivalents.
3.2.1 TE Router ID TLV
The TE Router ID TLV is a stable IPv4 address that is routable,
regardless of the state of each interface.
Similarly, for IPv6, it is useful to have a stable IPv6 address
identifying a TE node. The IPv6 TE Router ID TLV is defined in
section 4.1.
3.2.2 IPv4 Interface Address sub-TLV
This sub-TLV of the Extended IS Reachability TLV contains an
IPv4 address for the local end of a link. The equivalent IPv6
Interface Address sub-TLV is defined in section 4.2.
3.2.3 IPv4 Neighbor Address sub-TLV
This sub-TLV of the Extended IS Reachability TLV is used for
point-to-point links, and contains an IPv4 address for the neighbor's
end of a link. The equivalent IPv6 Neighbor Address sub-TLV is
defined in section 4.3.
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In order to build the IPv6 Neighbor Address sub-TLV, an IS needs to
be able to get hold of a global (or site-local) IPv6 address for the
interface from the peer. To achieve this, the IPv6 Global Interface
Address TLV is defined in section 4.5. This TLV is included in the
IIH PDU and contains global or site-local IPv6 interface address
information. The TLV is used in addition to the IPv6 Interface
Address TLV defined in [IPv6], which, when used in the IIH PDU,
carries only link-local addresses.
3.2.4 IPv6 SRLG TLV
The SRLG TLV (type 138) defined in [GMPLS] identifies the
corresponding link using either local/remote IPv4 addresses or link
local/remote identifiers, and includes a flags field to indicate
which type of identifier is used.
When only IPv6 is used, we may not have either of these means of
identifying the corresponding Extended IS Reachability TLV or link.
There is no back-compatible way to modify the SRLG TLV (type 138)
to identify the link by IPv6 addresses, and therefore we need a new
TLV.
The IPv6 SRLG TLV is defined in section 4.4.
4. IPv6 TE TLVs
4.1 IPv6 TE Router ID TLV
The IPv6 Traffic Engineering Router ID TLV is TLV type 140.
The IPv6 TE Router ID TLV contains a 16-octet IPv6 address. A
stable, global or site-local IPv6 address SHOULD be used, so that the
router ID provides a routable address, regardless of the state of
a node's interfaces.
If a router does not implement traffic engineering, it MAY include or
omit the IPv6 Traffic Engineering Router ID TLV. If a router
implements traffic engineering for IPv6, it MUST include this TLV in
its LSP. This TLV MUST NOT be included more than once in an LSP. If
the TLV occurs more than once in an LSP, all except the first
instance is ignored.
Implementations MUST NOT inject a /128 prefix for the IPv6 TE router
ID into their forwarding table because this can lead to forwarding
loops when interacting with systems that do not support this TLV.
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4.2 IPv6 Interface Address sub-TLV
The IPv6 Interface Address sub-TLV of the Extended IS Reachability
TLV has sub-TLV type 12. It contains a 16-octet IPv6 address for the
interface described by the (main) TLV. This sub-TLV can occur
multiple times.
Implementations MUST NOT inject a /128 prefix for the interface
address into their routing or forwarding table, because this can lead
to forwarding loops when interacting with systems that do not support
this sub-TLV.
If a router implements the basic TLV extensions described in [TE], it
MAY include or omit this sub-TLV. If a router implements IPv6
traffic engineering, it MUST include this sub-TLV (except on an
unnumbered point-to-point link, in which case the Link Local
Interface Identifiers sub-TLV is used instead).
This sub-TLV MUST NOT contain an IPv6 link-local address.
4.3 IPv6 Neighbor Address sub-TLV
The IPv6 Neighbor Address sub-TLV of the Extended IS Reachability TLV
has sub-TLV type 13. It contains a 16-octet IPv6 address for a
neighboring router on the link described by the (main) TLV. This
sub-TLV can occur multiple times.
Implementations MUST NOT inject a /128 prefix for the interface
address into their routing or forwarding table, because this can lead
to forwarding loops when interacting with systems that do not support
this sub-TLV.
If a router implements the basic TLV extensions described in [TE], it
MAY include or omit this sub-TLV. If a router implements IPv6
traffic engineering, it MUST include this sub-TLV for point-to-point
links (except on an unnumbered point-to-point link, in which case the
Link Local Interface Identifiers sub-TLV is used instead).
This sub-TLV MUST NOT contain an IPv6 link-local address.
4.4 IPv6 SRLG TLV
The IPv6 SRLG TLV has type 139. The TLV carries the Shared Risk Link
Group information (see Section "Shared Risk Link Group Information"
of [GMPLS-ROUTING]).
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It contains a data structure consisting of:
- 6 octets of System ID
- 1 octet of Pseudonode Number
- 1 octet flags
- 16 octets of IPv6 interface address
- (optional) 16 octets of IPv6 neighbor address
- (variable) list of SRLG values, where each element in the list
has 4 octets.
The following illustrates encoding of the Value field of the
IPv6 SRLG TLV.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| System ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| System ID (cont.) | Pseudonode num| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 interface address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 interface address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 interface address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 interface address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (optional) IPv6 neighbor address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 neighbor address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 neighbor address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 neighbor address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ............ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The neighbor is identified by its System Id (6-octets), plus one
octet to indicate the pseudonode number if the neighbor is on a
LAN interface.
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The flag octet indicates whether the IPv6 neighbor address is
included (set to 1), or not included (set to 0). Other values for
the flags field are reserved - an implementation receiving a value
for the flags field other than 0 or 1 SHOULD discard the TLV.
Note that this rule for processing the flags octet allows for future
extensibility of the IPv6 SRLG TLV. In particular, it allows
alternative means of identifying the corresponding link to be added
in the future. An implementation that does not understand such an
extension will simply discard the TLV, rather than attempting to
interpret the TLV incorrectly.
The length of this TLV is 24 + 4 * (number of SRLG values) + 16 (if
the IPv6 neighbor address is included).
To prevent an SRLG TLV and an IPv6 SRLG TLV in the same logical LSP
from contradicting each other, the following rules are applied.
- The IPv6 SRLG TLV MAY occur more than once within the IS-IS
logical LSP.
- There MUST NOT be more than one IPv6 SRLG TLV for a given link.
- The IPv6 SRLG TLV (type 139) MUST NOT be used to describe the
SRLGs for a given link if it is possible to use the SRLG TLV
(type 138).
In other words, if SRLGs are to be advertised for a link, and if
the Extended IS Reachability TLV describing a link contains IPv4
interface/neighbor address sub-TLVs or the link local identifiers
sub-TLV, then the SRLGs MUST be advertised in the SRLG TLV
(type 138).
4.5 IPv6 Global Interface Address TLV
The IPv6 Global Interface Address TLV is TLV type 233. The TLV
structure is identical to that of the IPv6 Interface Address TLV
defined in [IPv6], but the semantics are different. In particular,
the TLV is included in IIH PDUs for those interfaces using IPv6 TE
extensions. The TLV contains global or site-local IPv6 addresses
assigned to the interface that is sending the Hello.
The IPv6 Global Interface Address TLV is not used in LSPs.
5. Security Considerations
This document raises no new security considerations.
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6. IANA Considerations
This document defines the following new IS-IS TLV types that need to
be reflected in the IS-IS TLV code-point registry:
Type Description IIH LSP SNP
---- ---------------------- --- --- ---
139 IPv6 SRLG TLV n y n
140 IPv6 TE Router ID n y n
233 IPv6 Global Interface y n n
Address TLV
This document also defines the following new sub-TLV types of
top-level TLV 22 that need to be reflected in the IS-IS sub-TLV
registry for TLV 22:
Type Description Length
---- ------------------------------ --------
12 IPv6 Interface Address 16
13 IPv6 Neighbor Address 16
7. References
7.1 Normative References
[IS-IS] "Intermediate System to Intermediate System Intra-Domain
Routeing Exchange Protocol for use in Conjunction with the
Protocol for Providing the Connectionless-mode Network
Service (ISO 8473)", ISO 10589, 2002.
[IPv6] C. Hopps, "Routing IPv6 with IS-IS",
draft-ietf-isis-ipv6-05.txt, January 2003
(work in progress).
[TE] H. Smit and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
[GMPLS] K.Kompella and Y.Rekhter, "IS-IS Extensions in Support of
Generalized Multi-Protocol Label Switching",
draft-ietf-isis-gmpls-extensions-19.txt, October 2003
(work in progress).
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7.2 Informative References
[GMPLS-ROUTING]
K.Kompella and Y.Rekhter, "Routing Extensions in Support of
Generalized MPLS", draft-ietf-ccamp-gmpls-routing-09.txt,
October 2003 (work in progress).
8. Authors' Addresses
Jon Harrison
Data Connection Ltd
100 Church Street
Enfield
EN2 6BQ
U.K.
Phone: +44 20 8366 1177
Email: jon.harrison@dataconnection.com
Jon Berger
Data Connection Ltd
100 Church Street
Enfield
EN2 6BQ
U.K.
Phone: +44 20 8366 1177
Email: jon.berger@dataconnection.com
Mike Bartlett
Data Connection Ltd
100 Church Street
Enfield
EN2 6BQ
U.K.
Phone: +44 20 8366 1177
Email: mike.bartlett@dataconnection.com
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9. Full Copyright Statement
Copyright (C) The Internet Society 2004. This document is subject
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