Internet DRAFT - draft-ietf-mpls-ldp-multi-topology
draft-ietf-mpls-ldp-multi-topology
Internet Engineering Task Force Q. Zhao
Internet-Draft Huawei Technology
Intended status: Standards Track K. Raza
Expires: October 31, 2014 C. Zhou
Cisco Systems
L. Fang
Microsoft
L. Li
China Mobile
D. King
Old Dog Consulting
April 23, 2014
LDP Extensions for Multi Topology
draft-ietf-mpls-ldp-multi-topology-12.txt
Abstract
Multi-Topology (MT) routing is supported in IP networks with the use
of MT aware IGPs. In order to provide MT routing within
Multiprotocol Label Switching (MPLS) Label Distribution Protocol
(LDP) networks new extensions are required.
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 October 31, 2014.
Copyright Notice
Copyright (c) 2014 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . 7
3.5.1. Protocol Extension . . . . . . . . . . . . . . . . . . 7
3.5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . 8
3.6. Label Spaces . . . . . . . . . . . . . . . . . . . . . . . 10
3.7. 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 . . . . . . . . . . . . . . . . . . . 13
7. MPLS Forwarding in MT . . . . . . . . . . . . . . . . . . . . 14
8. Security Consideration . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. Manageability Considerations . . . . . . . . . . . . . . . . . 16
10.1. Control of Function and Policy . . . . . . . . . . . . . . 16
10.2. Information and Data Models . . . . . . . . . . . . . . . 16
10.3. Liveness Detection and Monitoring . . . . . . . . . . . . 16
10.4. Verify Correct Operations . . . . . . . . . . . . . . . . 16
10.5. Requirements On Other Protocols . . . . . . . . . . . . . 16
10.6. Impact On Network Operations . . . . . . . . . . . . . . . 17
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 17
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 18
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
13.1. Normative References . . . . . . . . . . . . . . . . . . . 18
13.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
Multi-Topology (MT) routing is supported in IP networks with the use
of MT aware IGPs. It would be advantageous for Communications
Service Providers (CSP) to support Multiple Topologies (MT) within
MPLS environments (MPLS-MT). The benefits of MPLS-MT
technology provide features for various network scenarios, including:
o A CSP may want to assign varying Quality of Service (QoS) profiles
to different traffic classes. based on a specific topology in an
MT routing network;
o Separate routing and MPLS domains may be used to isolate 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 may be divided from customer traffic using
different MTs utilizing separate links, thus ensuring that
management traffic is separated from 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 Forwarding
Equivalence Class (FEC) types for Label Switched Path (LSP) ping.
2. 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
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document are to be interpreted as described in RFC 2119 [RFC2119].
3. Signaling Extensions
3.1. Topology-Scoped Forwarding Equivalence Class (FEC)
LDP assigns and binds a label to a FEC, where a FEC is a list of one
or 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 implies 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 2.1) defines the
"Prefix" FEC Element. The "Prefix" encoding is defined for a given
"Address Family" (AF), and has length (in bits) 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 is
described 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: MT IP Address Family 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Address |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MT IPv6 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.
The definition and usage for the remaining fields in the FEC Elements
are 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 defined 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.
3.3. LDP FEC Elements with MT IP AF
The following section specifies the format extensions of the existing
LDP FEC Elements to support MT. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: MT Prefix FEC Element Format
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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 4: MT Typed Wildcard FEC Element
The above format can be used for any LDP FEC Element that allows use
of IP/IPv6 address family. In the scope of this document, the
allowed "FEC Type" in a MT Typed Wildcard FEC Element is "Prefix" 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 assigned, unassigned and special LDP MT-ID values
are requested In Section 9. (IANA Considerations).
How future LDP MT-ID values are allocated are out of of scope of this
document. Instead a new Internet-Draft will be created to document
the allocation policy and process for requesting new MT-ID values.
3.5. LDP MT Capability Advertisement
3.5.1. Protocol Extension
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. An LDP speaker MUST NOT send
messages containing MT FEC elements unless the peer has said it can
handle it.
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
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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 5: Multi-Topology Capability TLV Format
Where:
o U-bit: MUST be 1 so that the TLV will be silently ignored by a
recipient if it is unkown according to the rules of [RFC5036].
o F-bit: MUST be 0 as per Section 3 (Specifying Capabilities in LDP
Messages) 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: length of Value field, starting from S bit, in octets.
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. The MT-ID field of MT Typed Wildcard
FEC Element MUST be set to "Wildcard Topology" when it is
specified in MT Capability TLV.
3.5.2. Procedures
To announce its MT capability for an IP address family, LDP FEC type,
and Multi Topology, an LDP speaker sends 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
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IPv6" for IPv6 address family), corresponding "FEC Type" field (i.e.,
set to "Prefix"), 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 sends "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
any LDP messages with FEC elements that include MT identifier to
this LSR.
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 (if it supports Dynamic Announcement Capability). 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
initiates withdraw of all label mapping for existing LSPs of all
non-default MTs. It also cleans up all the LSPs of all non-
default MTs locally. Then it clears the S bit in MT capability
TLV and advertises via the Capability message (if it supports
Dynamic Announcement Capability). When an LSR knows the peer node
is changed from LDP-MT capable to non-MT capable, it cleanup all
the LSPs of all non-default MTs locally and initiate withdraw of
all label mapping for existing LSPs of all non-default MTs. Both
sides of the nodes send label release to its peer once they
receive the label release messages even both sides have already
cleaned up all the LSPs locally.
o If an LSR does not support "Dynamic Announcement Capability", it
MUST reset session with its peer whenever LSR changes its local
capability with regards to supporting LDP MT.
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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3.6. Label Spaces
The use of multiple topologies for LDP does not require different
label spaces for each topology. An LSR can use the same label space
for all MT FECs as for the default topology.
Similarly, signaling for different topologies can and should be done
within a single LDP session.
3.7. Reserved MT ID Values
Certain MT topologies are assigned to serve predetermined purposes.
In Section 9. (IANA Considerations), this document defines 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 Topology 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 defined 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.
The defined 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 de-configuration of a topology "x", an LSR
may send a typed wildcard label withdraw message with MT-ID "x" to
withdraw all its labels from the peer that advertised under the scope
of topology "x". Additionally, upon a global configuration change,
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an LSR may send a typed wildcard label withdraw message 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 allows 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. That 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 defines 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]:
Sub-Type Length Value Field
-------- ------ -----------------
TBA1 8 MT LDP IPv4 prefix
TBA2 20 MT LDP IPv6 prefix
Figure 6: 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
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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 7: 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:
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 8: 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
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ID). The Length for this sub-TLV is 17.
4.3.4. Operation Considerations
To detect data plane failures using LSP Ping for a specific topology,
the router will initiate an LSP Ping request with the target FEC
stack TLV containing LDP MT IP Prefix Sub-TLV in the Echo Request
packet. The Echo Request packet is sent with the label bound to the
IP Prefix in the topology. Once the echo request packet reaches the
target router, it will process the packet and perform checks 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 is not specified, the
reply packet must go through the default topology instead of the
topology where the Echo Request goes through.
It should be noted that existing MIB module for an MPLS LSR [RFC3813]
and MPLS LDP managed objects[RFC3815] do not provide the necessary
information to support the extensions in this document. For
example, the absence of the MT-ID as an index into the MIB modules
means that there is no way to disambiguate different topology
instances.
5. Error Handling
The extensions defined in this document utilize the existing LDP
error handling defined in [RFC5036]. If an LSR receives an error
notification from a peer for a session, it terminates the LDP session
by closing the TCP transport connection for the session and
discarding all multi-topology label mappings learned via the session.
5.1. MT Error Notification for Invalid Topology ID
An LSR should respond with an "Invalid Topology ID" status code in
LDP Notification message when it receives an LDP message with a FEC
element specifying an MT-ID which is not locally known or not
supported. The LSR MUST also discard the entire message before
sending the Notification.
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.
The legacy node which does not support MT should not receive any MT
related LDP messages. In case the bad things happen, according to
[RFC5036], processing of such messages should be aborted.
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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 feature allows the existing
data plane techniques to be used. Also, there is no way for the data
plane to associate a received packet with any one topology, meaning
that topology-specific label spaces cannot be used.
8. Security Consideration
The use of MT over existing MPLS solutions does not offer any
specific security benefit.
General LDP Communication security threats and how these may be
mitigated are described in [RFC5036], these threats include:
o Spoofing
o Privacy
o Denial of Service
For further discussion regarding possible LDP communication threats
and mitigation techniques see [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". We
suggest to have a value in the range 0x050C-0x05FF).
o New Status Code: "Invalid Topology ID" (requested code point: TBA2
from LDP registry "Status Code Name Space").
Registry:
Range/Value Description
-------------- ------------------------------
TBA2 Invalid Topology ID
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This new Status Code should be added to
the range 0x00000000-0x1FFFFFFF (IETF Consensus).
Figure 9: New Code Points 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 10: Address Family Numbers
o New registry "MPLS Multi-Topology Identifiers".
This registry should be a sub-registry of "Multiprotocol Label
Switching Architecture (MPLS)"
The allocation policies for this registry are:
Range/Value Purpose Reference
----------- ------------------------------------- ----------
0 Default/standard topology [This.I-D]
1 IPv4 in-band management [This.I-D]
2 IPv6 routing topology [This.I-D]
3 IPv4 multicast topology [This.I-D]
4 IPv6 multicast topology [This.I-D]
5 IPv6 in-band management [This.I-D]
6-3995 Unassigned for future IGP topologies [This.I-D]
Assigned by Standards Action [This.I-D]
3996-4095 Experimental [This.I-D]
4096-65534 Unassigned for MPLS topologies [This.I-D]
Assigned by Standards Action
65535 Wildcard Topology [This.I-D]
Figure 11: MPLS Multi-Topology Identifier registry
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
-------- -----------
TBA3 MT LDP IPv4 prefix
TBA4 MT LDP IPv6 prefix
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Figure 12: New Sub-TLV Types for LSP ping
IANA should allocate the next available numbers for these TBAs.
As highlighted at the end of Section 3.4 (IGP MT-ID Mapping and
Translation), a new Internet-Draft will be created to document the
policy and process for allocating new MT-ID values.
10. Manageability Considerations
10.1. Control of Function and Policy
There are capabilities that should be configurable to enable good
manageability. One such example is to allow enable or disable LDP
Multi-Topology capability. It is assumed that the mapping of the LDP
MT ID and IGP MT ID is manually configured on every router by
default. If an automatic mapping between IGP MT IDs and LDP MT IDs
is needed, there must be explicit configuration to do so.
10.2. Information and Data Models
Any extensions that may be required for existing MIBs are beyond the
scope of this document.
10.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements.
10.4. Verify Correct Operations
In order to debug an LDP MT enabled network it may be necessary to
associate between the LDP label advertisement and the IGP routing
advertisement, in this case the user MUST understand the mapping
mechanism to convert the IGP MT ID to the LDP MT ID. The method and
type of mapping mechanism is out of the scope of this document.
10.5. Requirements On Other Protocols
If the LDP MT ID has an implicit dependency on IGP MT ID, then the
corresponding IGP MT features will need to be supported.
10.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations.
11. Contributors
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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
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
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12. Acknowledgement
The authors would like to thank Dan Tappan, Nabil Bitar, Huang Xin,
Eric Rosen, IJsbrand Wijnands, Dimitri Papadimitriou, Yiqun Chai,
Pranjal Dutta, George Swallow, Curtis Villamizar, Adrian Farrel, Alia
Atlas and Loa Anderson for their valuable comments on this draft.
13. References
13.1. 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.
13.2. Informative References
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC3813] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Label Switching
Router (LSR) Management Information Base (MIB)", RFC 3813,
June 2004.
[RFC3815] Cucchiara, J., Sjostrand, H., and J. Luciani, "Definitions
of Managed Objects for the Multiprotocol Label Switching
(MPLS), Label Distribution Protocol (LDP)", RFC 3815,
June 2004.
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Authors' Addresses
Quintin Zhao
Huawei Technology
125 Nagog Technology Park
Acton, MA 01719
US
Email: quintin.zhao@huawei.com
Kamran Raza
Cisco Systems
2000 Innovation Drive
Kanata, ON K2K-3E8, MA
Canada
Email: E-mail: skraza@cisco.com
Chao Zhou
Cisco Systems
300 Beaver Brook Road
Boxborough, MA 01719
US
Email: czhou@cisco.com
Luyuan Fang
Microsoft
Email: lufang@microsoft.com
Lianyuan Li
China Mobile
53A, Xibianmennei Ave.
Xunwu District, Beijing 01719
China
Email: lilianyuan@chinamobile.com
Daniel King
Old Dog Consulting
Email: daniel@olddog.co.uk
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