Internet Engineering Task Force Q. Zhao
Internet-Draft Huawei Technology
Intended status: Standards Track L. Fang
Updates: 4379 C. Zhou
Expires: November 13, 2013 Cisco Systems
L. Li
China Mobile
K. Raza
Cisco Systems
May 13, 2013
LDP Extensions for Multi Topology Routing
draft-ietf-mpls-ldp-multi-topology-08.txt
Abstract
Multi-Topology (MT) routing is supported in IP networks with the use
of MT aware IGP protocols. In order to provide MT routing within
Multiprotocol Label Switching (MPLS) Label Distribution Protocol
(LDP) networks new extensions are required. This document updates
RFC4379.
This document describes the LDP protocol extensions required to
support MT routing in an MPLS environment.
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 http://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."
This Internet-Draft will expire on November 13, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 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.
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Signaling Extensions . . . . . . . . . . . . . . . . . . . . . 5
3.1. Topology-Scoped Forwarding Equivalence Class (FEC) . . . . 5
3.2. New Address Families: MT IP . . . . . . . . . . . . . . . 5
3.3. LDP FEC Elements with MT IP AF . . . . . . . . . . . . . . 6
3.4. IGP MT-ID Mapping and Translation . . . . . . . . . . . . 7
3.5. LDP MT Capability Advertisement . . . . . . . . . . . . . 8
3.6. Procedures . . . . . . . . . . . . . . . . . . . . . . . . 9
3.7. LDP Sessions . . . . . . . . . . . . . . . . . . . . . . . 10
3.8. Reserved MT ID Values . . . . . . . . . . . . . . . . . . 10
4. MT Applicability on FEC-based features . . . . . . . . . . . . 10
4.1. Typed Wildcard FEC Element . . . . . . . . . . . . . . . . 10
4.2. End-of-LIB . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3. LSP Ping . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3.1. New FEC Sub-Types . . . . . . . . . . . . . . . . . . 11
4.3.2. MT LDP IPv4 FEC Sub-TLV . . . . . . . . . . . . . . . 12
4.3.3. MT LDP IPv6 FEC Sub-TLV . . . . . . . . . . . . . . . 12
4.3.4. Operation Considerations . . . . . . . . . . . . . . . 13
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. MT Error Notification for Invalid Topology ID . . . . . . 13
6. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 14
7. MPLS Forwarding in MT . . . . . . . . . . . . . . . . . . . . 14
8. Security Consideration . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16
11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 17
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . 18
A.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 18
A.2. Application Scenarios . . . . . . . . . . . . . . . . . . 18
A.2.1. Simplified Data-plane . . . . . . . . . . . . . . . . 18
A.2.2. Using MT for P2P Protection . . . . . . . . . . . . . 19
A.2.3. Using MT for mLDP Protection . . . . . . . . . . . . . 19
A.2.4. Service Separation . . . . . . . . . . . . . . . . . . 19
A.2.5. An Alternative Inter-AS VPN Solution . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Terminology
This document uses MPLS terminology defined in [RFC5036]. Additional
terms are defined below:
o MT-ID: A 16 bit value used to represent the Multi-Topology ID.
o Default MT Topology: A topology that is built using the MT-ID
default value of 0.
o MT Topology: A topology that is built using the corresponding
MT-ID.
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 [RFC2119].
2. Introduction
Multi-Topology (MT) routing is supported in IP networks with the use
of MT aware IGP protocols. It would be advantageous for
communications Service Providers (CSP) to support Multiple Topologies
(MT) within MPLS environments (MPLS-MT). The benefits of MPLS-MT
enabled networks include:
o A CSP may want to assign varying QoS profiles to traffic, based on
a specific MT.
o Separate routing and MPLS domains may be used to isolated
multicast and IPv6 islands within the backbone network.
o Specific IP address space could be routed across an MT based on
security or operational isolation requirements.
o Low latency links could be assigned to an MT for delay sensitive
traffic.
o Management traffic could be separated from customer traffic using
multiple MTs, where the management traffic MT does not use links
that carries customer traffic.
This document describes the Label Distribution Protocol (LDP)
procedures and protocol extensions required to support MT routing in
an MPLS environment.
This document also updates RFC4379 by defining two new FEC types for
LSP ping.
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3. Signaling Extensions
3.1. Topology-Scoped Forwarding Equivalence Class (FEC)
LDP assigns and binds a label to a Forwarding Equivalence Class
(FEC), where a FEC is a list of one of more FEC elements. To setup
LSPs for unicast IP routing paths, LDP assigns local labels for IP
prefixes, and advertises these labels to its peers so that an LSP is
setup along the routing path. To setup MT LSPs for IP prefixes under
a given topology scope, the LDP "prefix-related" FEC element must be
extended to include topology information. This infers that MT-ID
becomes an attribute of Prefix-related FEC element, and all FEC-Label
binding operations are performed under the context of given topology
(MT-ID).
The following Subsection 3.2(New Address Families (AF): MT IP)
defines the extension required to bind "prefix-related" FEC to a
topology.
3.2. New Address Families: MT IP
The LDP base specification [RFC5036] (Section 4.1) defines the
"Prefix" FEC Element 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix (2) | Address Family | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Prefix FEC Element Format [RFC5036]
Where "Prefix" encoding is as defined for given "Address Family"
(AF), and whose length (in bits) is specified by the "PreLen" field.
To extend IP address families for MT, two new Address Families named
"MT IP" and "MT IPv6" are used to specify IPv4 and IPv6 prefixes
within a topology scope.
The format of data associated with these new Address Families are
described below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MT IP Address Family Format
Where "IP Address" is an IPv4 and IPv6 address/prefix for "MT IP" and
"MT IPv6" AF respectively, and the field "MT-ID" corresponds to 16-
bit Topology ID for given address.
Where 16-bit "MT-ID" field defines the Topology ID, and the
definition and usage of the rest fields in the FEC Elements are same
as defined for IP/IPv6 AF. The value of MT-ID 0 corresponds to
default topology and MUST be ignored on receipt so as to not cause
any conflict/confusion with existing non-MT procedures.
The proposed FEC Elements with "MT IP" Address Family can be used in
any LDP message and procedures that currently specify and allow the
use of FEC Elements with IP/IPv6 Address Family.
[RFC5036] does not specify the handling of "Unknown" Address
Families. Therefore, [RFC5036] will need to be updated to include
the handling procedure for unknown address families.
3.3. LDP FEC Elements with MT IP AF
The following section specifies the format extensions of the existing
LDP FEC Elements. The "Address Family" of these FEC elements will be
set to "MT IP" or "MT IPv6".
The MT Prefix FEC element encoding is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix (2) | Address Family (MT IP/MT IPv6)| PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 3: MT Prefix FEC Element Format
Similarly, the MT mLDP FEC elements encoding is as follows, where the
mLDP FEC Type can be P2MP(6), MP2MP-up(7), and MP2MP-down(8):
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| mLDP FEC Type | Address Family (MT IP/MT IPv6)| Address Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Root Node Address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Length | Opaque Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: MT mLDP FEC Element Format
The MT Typed Wildcard FEC element encoding is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Typed Wcard (5)| FEC Type | Len = 6 | AF = MT IP ..|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|... or MT IPv6 | MT ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: MT Typed Wildcard FEC Element
3.4. IGP MT-ID Mapping and Translation
The non-reserved non-special IGP MT-ID values can be used and carried
in LDP without the need for translation. However, there is a need
for translating reserved or special IGP MT-ID values to corresponding
LDP MT-IDs. The corresponding special and reserved LDP MT-ID
values are requested In Section 9. (IANA Considerations).
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3.5. LDP MT Capability Advertisement
We specify a new LDP capability, named "Multi-Topology (MT)", which
is defined in accordance with LDP Capability definition guidelines
[RFC5561]. The LDP "MT" capability can be advertised by an LDP
speaker to its peers either during the LDP session initialization or
after the LDP session is setup to announce LSR capability to support
MT for the given IP address family.
The MT capability is specified using "Multi-Topology Capability"
TLV. The "Multi-Topology Capability" TLV format is in accordance
with LDP capability guidelines as defined in [RFC5561]. To be able
to specify IP address family, the capability specific data (i.e.
"Capability Data" field of Capability TLV) is populated using "Typed
Wildcard FEC Element" as defined in [RFC5918].
The format of "Multi-Topology Capability" TLV is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Multi-Topology Cap.(IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | |
+-+-+-+-+-+-+-+-+ |
~ Typed Wildcard FEC element(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Multi-Topology Capability TLV Format
Where:
o U- and F-bits: MUST be 1 and 0, respectively, as per Section 3.
(Signaling Extensions) of LDP Capabilities [RFC5561].
o Multi-Topology Capability: Capability TLV type (IANA assigned)
o S-bit: MUST be 1 if used in LDP "Initialization" message. MAY be
set to 0 or 1 in dynamic "Capability" message to advertise or
withdraw the capability respectively.
o Typed Wildcard FEC element(s): One or more elements specified as
the "Capability data".
o Length: The length (in octets) of TLV.
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o The encoding of Typed Wildcard FEC element, as defined in
[RFC5918], is defined in the section 3.3 (Typed Wildcard FEC
Element) of this document.
3.6. Procedures
To announce its MT capability for an IP address family, LDP FEC type,
and Multi Topology, an LDP speaker MAY send an "MT Capability"
including the exact Typed Wildcard FEC element with corresponding
"AddressFamily" field (i.e., set to "MT IP" for IPv4 and set to "MT
IPv6" for IPv6 address family), corresponding "FEC Type" field (i.e.,
set to "P2P", "P2MP", "MP2MP"), and corresponding "MT-ID". To
announce its MT capability for both IPv4 and IPv6 address family, or
for multiple FEC types, or for multiple Multi Topologies, an LDP
speaker MAY send "MT Capability" with one or more MT Typed FEC
elements in it.
o The capability for supporting multi-topology in LDP can be
advertised during LDP session initialization stage by including
the LDP MT capability TLV in LDP Initialization message. After an
LDP session is established, the MT capability can also be
advertised or withdrawn using Capability message (only if "Dynamic
Announcement" capability [RFC5561] has already been successfully
negotiated).
o If an LSR has not advertised MT capability, its peer must not send
messages that include MT identifier to this LSR.
o If an LSR receives a Label Mapping message with an MT parameter
from downstream LSR-D and its upstream LSR-U has not advertised MT
capability, an LSP for the MT will not be established.
o This document proposes to add a new notification event to signal
the upstream that the downstream is not capable.
o If an LSR is changed from non-MT capable to MT capable, it sets
the S bit in MT capability TLV and advertises via the Capability
message. The existing LSP is treated as LSP for default MT (ID
0).
o If an LSR is changed from LDP-MT capable to non-MT capable, it may
initiate withdraw of all label mapping for existing LSPs of all
non-default MTs. Then it clears the S bit in MT capability TLV
and advertises via the Capability message.
o If an LSR is changed from IGP-MT capable to non-MT capable, it may
wait until the routes update to withdraw FEC and release the label
mapping for existing LSPs of specific MT.
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3.7. LDP Sessions
Since using different label spaces for different topologies would
imply significant changes to the data plane, a single global label
space is supported in this solution. There will be one session
supported for each pair of peer, even there are multiple topologies
supported between these two peers.
3.8. Reserved MT ID Values
Certain MT topologies are assigned to serve predetermined purposes:
Default-MT: Default topology. This corresponds to OSPF default IPv4
and IPv6, as well as ISIS default IPv4. A value of 0 is proposed.
ISIS IPv6 MT: ISIS default MT-ID for IPv6.
Wildcard-MT: This corresponds to All-Topologies. A value of 65535
(0xffff) is proposed.
In Section 9. (IANA Considerations) this document proposes a new
IANA registry "LDP Multi-Topology ID Name Space" under IANA "LDP
Parameter" namespace to keep an LDP MT-ID reserved value.
If an LSR receives a FEC element with an "MT-ID" value that is
"Reserved" for future use (and not IANA allocated yet), the LSR must
abort the processing of the FEC element, and SHOULD send a
notification message with status code "Invalid MT-ID" to the sender.
4. MT Applicability on FEC-based features
4.1. Typed Wildcard FEC Element
[RFC5918] extends base LDP and defines Typed Wildcard FEC Element
framework. Typed Wildcard FEC element can be used in any LDP message
to specify a wildcard operation/action for given type of FEC.
The MT extensions proposed in document do not require any extension
to procedures for Typed Wildcard FEC element, and these procedures
apply as-is to MT wildcarding. The MT extensions, though, allow use
of "MT IP" or "MT IPv6" in the Address Family field of the Typed
Wildcard FEC element in order to use wildcard operations in the
context of a given topology. The use of MT-scoped address family
also allows us to specify MT-ID in these operations.
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The proposed format in Section 3.3 (Typed Wildcard FEC Element)
allows an LSR to perform wildcard FEC operations under the scope of a
topology. If an LSR wishes to perform wildcard operation that
applies to all topologies, it can use a "Wildcard Topology" MT-ID.
For example, upon local configuration of topology "x", an LSR may
send a wildcard label withdraw request with MT-ID "x" to withdraw all
its labels from the peer that advertized under the scope of topology
"x". Additionally, upon a global configuration change, an LSR may
send a wildcard label withdraw with the MT-ID set to "Wildcard
Topology" to withdraw all its labels under all topologies from the
peer.
4.2. End-of-LIB
[RFC5919] specifies extensions and procedures for an LDP speaker to
signal its convergence for a given FEC type towards a peer. The
procedures defined in [RFC5919] applies as-is to an MT FEC element.
This MAY allow an LDP speaker to signal its IP convergence using
Typed Wildcard FEC element, and its MT IP convergence per topology
using a MT Typed Wildcard FEC element.
4.3. LSP Ping
[RFC4379] defines procedures to detect data-plane failures in MPLS
LSPs via LSP ping. The specification defines a "Target FEC Stack"
TLV that describes the FEC stack being tested. This TLV is sent in
an MPLS echo request message towards LSPs egress LSR, and is
forwarded along the same data path as other packets belonging to the
FEC.
"Target FEC Stack" TLV contains one or more sub-TLVs pertaining to
different FEC types. Section 3.2 of [RFC4379] defines Sub-Types and
format for the FEC. To support LSP ping for MT LDP LSPs, this
document proposes following extensions to [RFC4379].
4.3.1. New FEC Sub-Types
We define two new FEC types for LSP ping:
o MT LDP IPv4 FEC
o MT LDP IPv6 FEC
We also define following new sub-types for sub-TLVs to specify these
FECs in the "Target FEC Stack" TLV of [RFC4379]:
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Sub-Type Length Value Field
-------- ------ -----------------
TBA5 5 MT LDP IPv4 prefix
TBA6 17 MT LDP IPv6 prefix
Figure 7: new sub-types for sub-TLVs
The rules and procedures of using these sub-TLVs in an MPLS echo
request message are same as defined for LDP IPv4/IPv6 FEC sub-TLV
types in [RFC4379].
4.3.2. MT LDP IPv4 FEC Sub-TLV
The format of "MT LDP IPv4 FEC" sub-TLV to be used in a "Target FEC
Stack" [RFC4379] is:
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 = TBA5(MT LDP IPv4 FEC) | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | MBZ | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: MT LDP IPv4 FEC sub-TLV
The format of this sub-TLV is similar to LDP IPv4 FEC sub-TLV as
defined in [RFC4379]. In addition to "IPv4 prefix" and "Prefix
Length" fields, this new sub-TLV also specifies MT-ID (Multi-Topology
ID). The Length for this sub-TLV is 5.
4.3.3. MT LDP IPv6 FEC Sub-TLV
The format of "MT LDP IPv6 FEC" sub-TLV to be used in a "Target FEC
Stack" [RFC4379] is:
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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 = TBA6(MT LDP IPv6 FEC) | Length = 20 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 prefix |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | MBZ | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: MT LDP IPv6 FEC sub-TLV
The format of this sub-TLV is similar to LDP IPv6 FEC sub-TLV as
defined in [RFC4379]. In addition to "IPv6 prefix" and "Prefix
Length" fields, this new sub-TLV also specifies MT-ID (Multi-Topology
ID). The Length for this sub-TLV is 17.
4.3.4. Operation Considerations
When detect data plane failures using LSP Ping for a specific topoly,
the router will intiate an LSP Ping request with the targer FEC stack
TLV containing LDP MT IP Prefix Sub-TLV in the Echo Request packet.
The Echo Request packet is sent with the label binded to the IP
Prefix in the topolgy. Once the echo request packet reaches the
target router, it will process the packet and perform checs for the
LDP MT IP Prefix sub-TLV present in the Target FEC Stack as described
in [RFC4379] and respond according to [RFC4379] processing rules.
For the case that the LSP ping with return path not specified , the
reply packet may go through the default topology instead of the
topology where the Echo Request goes through.
5. Error Handling
The extensions defined in this document utilise the existing LDP
error handling defined in [RFC5036]. If an LSR receives an error
notification from a peer for an MPLS-MT session, it terminates the
LDP session by closing the TCP transport connection for the session
and discarding all MT-ID label mappings learned via the session.
5.1. MT Error Notification for Invalid Topology ID
If an LSR has advertized an MT Capability TLV using the
Initialization message or Capability message, which includes Typed
Wildcard FEC elements with specific MT-IDs, and it receives an MT
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message with a MT-ID which is not included in the supported list, it
should response this "Invalid Topology ID" status code.
6. Backwards Compatibility
The MPLS-MT solution is backwards compatible with existing LDP
enhancements defined in [RFC5036], including message authenticity,
integrity of message, and topology loop detection.
7. MPLS Forwarding in MT
Although forwarding is out of the scope of this draft, we include
some forwarding consideration for informational purpose here.
The specified signaling mechanisms allow all the topologies to share
the platform-specific label space; this is the feature that allows
the existing data plane techniques to be used; and the specified
signaling mechanisms do not provide any way for the data plane to
associate a given packet with a context-specific label space.
8. Security Consideration
No specific security issues with the proposed solutions are known.
The proposed extensions in this document do not introduce any new
security considerations beyond that already apply to the base LDP
specification [RFC5036] and [RFC5920].
9. IANA Considerations
The document introduces following new protocol elements that require
IANA consideration and assignments:
o New LDP Capability TLV: "Multi-Topology Capability" TLV (requested
code point: TBA1 from LDP registry "TLV Type Name Space").
o New Status Code: "Multi-Topology Capability not supported"
(requested code point: TBA2 from LDP registry "Status Code Name
Space").
o New Status Code: "Invalid Topology ID" (requested code point: TBA3
from LDP registry "Status Code Name Space").
o New Status Code: "Unknown Address Family" (requested code point:
TBA4 from LDP registry "Status Code Name Space").
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Registry:
Range/Value E Description
-------------- --- ------------------------------
0x00000051 1 Invalid Topology ID
Figure 10: New Status Codes for LDP Multi Topology Extensions
o New address families under IANA registry "Address Family Numbers":
- MT IP: Multi-Topology IP version 4 (requested codepoint: 26)
- MT IPv6: Multi-Topology IP version 6 (requested codepoint: 27)
Figure 11: Address Family Numbers
o New registry "LDP Multi-Topology (MT) ID Name Space" under "LDP
Parameter" namespace. The registry is defined as:
Range/Value Name
----------- ------------------------
0 Default Topology (ISIS and OSPF)
1-4095 Unassigned
4096 ISIS IPv6 routing topology
(i.e. ISIS MT ID #2)
4097-65534 Reserved (for future allocation)
65535 Wildcard Topology (ISIS or OSPF)
Figure 12: LDP Multi-Topology (MT) ID Name Space
o New Sub-TLV Types for LSP ping: Following new sub-type values
under TLV type 1 (Target FEC Stack) from "Multi-Protocol Label
Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
registry, and "TLVs and sub-TLVs" sub-registry.
Sub-Type Value Field
-------- -----------
TBA5 MT LDP IPv4 prefix
TBA6 MT LDP IPv6 prefix
Figure 13: New Sub-TLV Types for LSP ping
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10. Contributors
Ning So
Tata Communications
2613 Fairbourne Cir.
Plano, TX 75082
USA
Email: ning.so@tatacommunications.com
Raveendra Torvi
Juniper Networks
10, Technoogy Park Drive
Westford, MA 01886-3140
US
Email: rtorvi@juniper.net
Huaimo Chen
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
US
Email: huaimochen@huawei.com
Emily Chen
2717 Seville Blvd, Apt 1205,
Clearwater, FL 33764
US
Email: emily.chen220@gmail.com
Chen Li
China Mobile
53A, Xibianmennei Ave.
Xunwu District, Beijing 01719
China
Email: lichenyj@chinamobile.com
Lu Huang
China Mobile
53A, Xibianmennei Ave.
Xunwu District, Beijing 01719
China
Email: huanglu@chinamobile.com
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Daniel King
Old Dog Consulting
Email: E-mail: daniel@olddog.co.uk
Zhenbin Li
Huawei Technology
2330 Central Expressway
Santa Clara, CA 95050
US
Email: zhenbin.li@huawei.com
11. Acknowledgement
The authors would like to thank Dan Tappan, Nabil Bitar, Huang Xin,
Eric Rosen, IJsbrand Wijnands, Dimitri Papadimitriou, Yiqun Chai and
pranjal Dutta, George Swallow and Curtis Villamizar for their
valuable comments on this draft.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL.
Le Roux, "LDP Capabilities", RFC 5561, July 2009
[RFC5918] Asati, R., Minei, I., and B. Thomas, "Label Distribution
Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class
(FEC)", RFC 5918, August 2010.
[RFC5919] Asati, R., Mohapatra, P., Chen, E., and B. Thomas,
"Signaling LDP Label Advertisement Completion", RFC 5919,
August 2010.
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12.2. Informative References
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
Authors' Addresses
Quintin Zhao
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
US
Email: quintin.zhao@huawei.com
Luyuan Fang
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
US
Email: lufang@cisco.com
Chao Zhou
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
US
Email: czhou@cisco.com
Lianyuan Li
China Mobile
53A, Xibianmennei Ave.
Xunwu District, Beijing 01719
China
Email: lilianyuan@chinamobile.com
Kamran Raza
Cisco Systems
2000 Innovation Drive
Kanata, ON K2K-3E8, MA
Canada
Email: E-mail: skraza@cisco.com
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