Network Working Group Seisho Yasukawa (Editor)
Internet-Draft NTT
Intended Status: Standards Track Adrian Farrel (Editor)
Created: June 1, 2008 Old Dog Consulting
Expires: December 1, 2008
Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol
Label Switching (MPLS) - Extensions to LSP Ping
draft-ietf-mpls-p2mp-lsp-ping-06.txt
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Abstract
Recent proposals have extended the scope of Multiprotocol Label
Switching (MPLS) Label Switched Paths (LSPs) to encompass
point-to-multipoint (P2MP) LSPs.
The requirement for a simple and efficient mechanism that can be
used to detect data plane failures in point-to-point (P2P) MPLS LSPs
has been recognised and has led to the development of techniques
for fault detection and isolation commonly referred to as "LSP Ping".
The scope of this document is fault detection and isolation for P2MP
MPLS LSPs. This documents does not replace any of the mechanisms of
LSP Ping, but clarifies their applicability to MPLS P2MP LSPs, and
extends the techniques and mechanisms of LSP Ping to the MPLS P2MP
environment.
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Conventions used in this document
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].
Contents
1. Introduction ................................................... 4
1.1 Design Considerations ......................................... 4
2. Notes on Motivation ............................................ 5
2.1. Basic Motivations for LSP Ping ............................... 5
2.2. Motivations for LSP Ping for P2MP LSPs ....................... 6
2.3 Bootstrapping Other OAM Procedures Using LSP Ping ............. 7
3. Operation of LSP Ping for a P2MP LSP ........................... 8
3.1. Identifying the LSP Under Test ............................... 8
3.1.1. Identifying a P2MP MPLS TE LSP ............................. 8
3.1.1.1. RSVP P2MP IPv4 Session Sub-TLV ........................... 9
3.1.1.2. RSVP P2MP IPv6 Session Sub-TLV ........................... 9
3.1.2. Identifying a Multicast LDP LSP ........................... 10
3.1.2.1. Multicast LDP FEC Stack Sub-TLV ......................... 10
3.2. Ping Mode Operation ......................................... 11
3.2.1. Controlling Responses to LSP Pings ........................ 11
3.2.2. Ping Mode Egress Procedures ............................... 12
3.2.3. Jittered Responses ........................................ 12
3.2.4. P2MP Egress Identifier TLV and Sub-TLVs ................... 13
3.2.5. Echo Jitter TLV ........................................... 14
3.3. Traceroute Mode Operation ................................... 14
3.3.1. Traceroute Responses at Non-Branch Nodes .................. 15
3.3.1.1. Correlating Traceroute Responses ........................ 15
3.3.2. Traceroute Responses at Branch Nodes ..................... 16
3.3.2.1. Correlating Traceroute Responses ........................ 17
3.3.3. Traceroute Responses at Bud Nodes ......................... 17
3.3.4. Non-Response to Traceroute Echo Requests .................. 17
3.3.5. Modifications to the Downstream Mapping TLV ............... 18
3.3.6. Additions to Downstream Mapping Multipath Information ..... 19
4. Operation of LSP Ping for Bootstrapping Other OAM Mechanisms .. 20
5. Non-compliant Routers ......................................... 20
6. OAM Considerations ............................................ 20
7. IANA Considerations ........................................... 21
7.1. New Sub-TLV Types ........................................... 21
7.2. New Multipath Type .......................................... 21
7.3. New TLVs .................................................... 22
8. Security Considerations ....................................... 22
9. Acknowledgements .............................................. 22
10. Intellectual Property Considerations ......................... 23
11. Normative References ......................................... 23
12. Informative References ....................................... 23
13. Authors' Addresses ........................................... 24
14. Full Copyright Statement ..................................... 25
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0. Change Log
This section to be removed before publication as an RFC.
0.1 Changes from 00 to 01
- Update references.
- Fix boilerplate.
0.2 Changes from 01 to 02
- Update entire document so that it is not specific to MPLS-TE, but
also includes multicast LDP LSPs.
- Move the egress identifier sub-TLVs from the FEC Stack TLV to a new
egress identifier TLV.
- Include Multicast LDP FEC Stack sub-TLV definition from [MCAST-CV].
- Add brief section on use of LSP Ping for bootstrapping.
- Add new references to References section.
- Add details of two new authors.
0.3 Changes from 02 to 03
- Update references.
- Update boilerplate.
- Fix typos.
- Clarify in 3.2.2 that a recipient of an echo request must reply
only once it has applied incoming rate limiting.
- Tidy references to bootstrapping for [MCAST-CV] in 1.1.
- Allow multiple sub-TLVs in the P2MP Egress Identifier TLV in
sections 3.2.1, 3.2.2, 3.2.4, 3.3.1, and 3.3.4.
- Clarify how to handle a P2MP Egress Identifier TLV with no sub-TLVs
in sections 3.2.1 and 3.2.2.
0.4 Changes from 03 to 04
- Revert to previous text in sections 3.2.1, 3.2.2, 3.2.4, 3.3.1, and
3.3.4 with respect to multiple sub-TLVs in the P2MP Egress
Identifier TLV.
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0.5 Changes from 04 to 05
- Change coordinates for Tom Nadeau. Section 13.
- Fix typos.
- Update references.
- Resolve all acronym expansions.
1. Introduction
Simple and efficient mechanisms that can be used to detect data plane
failures in point-to-point (P2P) Multiprotocol Label Switching (MPLS)
Label Switched Paths (LSP) are described in [RFC4379]. The techniques
involve information carried in an MPLS "echo request" and "echo
reply", and mechanisms for transporting the echo reply. The echo
request and reply messages provide sufficient information to check
correct operation of the data plane, as well as a mechanism to verify
the data plane against the control plane, and thereby localize
faults. The use of reliable channels for echo reply messages as
described in [RFC4379] enables more robust fault isolation. This
collection of mechanisms is commonly referred to as "LSP Ping".
The requirements for point-to-multipoint (P2MP) MPLS traffic
engineered (TE) LSPs are stated in [RFC4461]. [RFC4875] specifies a
signaling solution for establishing P2MP MPLS TE LSPs.
The requirements for point-to-multipoint extensions to the Label
Distribution Protocol (LDP) are stated in [P2MP-LDP-REQ]. [P2MP-LDP]
specifies extensions to LDP for P2MP MPLS.
P2MP MPLS LSPs are at least as vulnerable to data plane faults or to
discrepancies between the control and data planes as their P2P
counterparts. Mechanisms are, therefore, desirable to detect such
data plane faults in P2MP MPLS LSPs as described in [RFC4687].
This document extends the techniques described in [RFC4379] such
that they may be applied to P2MP MPLS LSPs and so that they can be
used to bootstrap other Operations and Management (OAM) procedures
such as [MCAST-CV]. This document stresses the reuse of existing LSP
Ping mechanisms used for P2P LSPs, and applies them to P2MP MPLS LSPs
in order to simplify implementation and network operation.
1.1 Design Considerations
An important consideration for designing LSP Ping for P2MP MPLS LSPs
is that every attempt is made to use or extend existing mechanisms
rather than invent new mechanisms.
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As for P2P LSPs, a critical requirement is that the echo request
messages follow the same data path that normal MPLS packets traverse.
However, it can be seen this notion needs to be extended for P2MP
MPLS LSPs, as in this case an MPLS packet is replicated so that it
arrives at each egress (or leaf) of the P2MP tree.
MPLS echo requests are meant primarily to validate the data plane,
and they can then be used to validate data plane state against the
control plane. They may also be used to bootstrap other OAM
procedures such as [MPLS-BFD] and [MCAST-CV]. As pointed out in
[RFC4379], mechanisms to check the liveness, function, and
consistency of the control plane are valuable, but such mechanisms
are not a feature of LSP Ping and are not covered in this document.
As is described in [RFC4379], to avoid potential Denial of Service
attacks, it is RECOMMENDED to regulate the LSP Ping traffic passed to
the control plane. A rate limiter should be applied to the well-known
UDP port defined for use by LSP Ping traffic.
2. Notes on Motivation
2.1. Basic Motivations for LSP Ping
The motivations listed in [RFC4379] are reproduced here for
completeness.
When an LSP fails to deliver user traffic, the failure cannot always
be detected by the MPLS control plane. There is a need to provide a
tool that enables users to detect such traffic "black holes" or
misrouting within a reasonable period of time. A mechanism to isolate
faults is also required.
[RFC4379] describes a mechanism that accomplishes these goals. This
mechanism is modeled after the ping/traceroute paradigm: ping (ICMP
echo request [RFC792]) is used for connectivity checks, and
traceroute is used for hop-by-hop fault localization as well as path
tracing. [RFC4379] specifies a "ping mode" and a "traceroute" mode
for testing MPLS LSPs.
The basic idea as expressed in [RFC4379] is to test that the packets
that belong to a particular Forwarding Equivalence Class (FEC)
actually end their MPLS path on an LSR that is an egress for that
FEC. [RFC4379] achieves this test by sending a packet (called an
"MPLS echo request") along the same data path as other packets
belonging to this FEC. An MPLS echo request also carries information
about the FEC whose MPLS path is being verified. This echo request is
forwarded just like any other packet belonging to that FEC. In "ping"
mode (basic connectivity check), the packet should reach the end of
the path, at which point it is sent to the control plane of the
egress LSR, which then verifies that it is indeed an egress for the
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FEC. In "traceroute" mode (fault isolation), the packet is sent to
the control plane of each transit LSR, which performs various checks
that it is indeed a transit LSR for this path; this LSR also returns
further information that helps to check the control plane against the
data plane, i.e., that forwarding matches what the routing protocols
determined as the path.
One way these tools can be used is to periodically ping a FEC to
ensure connectivity. If the ping fails, one can then initiate a
traceroute to determine where the fault lies. One can also
periodically traceroute FECs to verify that forwarding matches the
control plane; however, this places a greater burden on transit LSRs
and should be used with caution.
2.2. Motivations for LSP Ping for P2MP LSPs
As stated in [RFC4687], MPLS has been extended to encompass P2MP
LSPs. As with P2P MPLS LSPs, the requirement to detect, handle, and
diagnose control and data plane defects is critical. For operators
deploying services based on P2MP MPLS LSPs, the detection and
specification of how to handle those defects is important because
such defects may affect the fundamentals of an MPLS network, but also
because they may impact service level specification commitments for
customers of their network.
P2MP LDP [P2MP-LDP] uses the Label Distribution Protocol to establish
multicast LSPs. These LSPs distribute data from a single source to
one or more destinations across the network according to the next
hops indicated by the routing protocols. Each LSP is identified by an
MPLS multicast FEC.
P2MP MPLS TE LSPs [RFC4875] may be viewed as MPLS tunnels with a
single ingress and multiple egresses. The tunnels, built on P2MP
LSPs, are explicitly routed through the network. There is no concept
or applicability of a FEC in the context of a P2MP MPLS TE LSP.
MPLS packets inserted at the ingress of a P2MP LSP are delivered
equally (barring faults) to all egresses. In consequence, the basic
idea of LSP Ping for P2MP MPLS TE LSPs may be expressed as an
intention to test that packets that enter (at the ingress) a
particular P2MP LSP actually end their MPLS path on the LSRs that are
the (intended) egresses for that LSP. The idea may be extended to
check selectively that such packets reach specific egresses.
The technique in this document makes this test by sending an LSP Ping
echo request message along the same data path as the MPLS packets. An
echo request also carries the identification of the P2MP MPLS LSP
(multicast LSP or P2MP TE LSP) that it is testing. The echo request
is forwarded just as any other packet using that LSP, and so is
replicated at branch points of the LSP and should be delivered to all
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egresses. In "ping" mode (basic connectivity check), the echo request
should reach the end of the path, at which point it is sent to the
control plane of the egress LSRs, which verify that they are indeed
an egress (leaf) of the P2MP LSP. An echo response message is sent by
an egress to the ingress to confirm the successful receipt (or
announce the erroneous arrival) of the echo request.
In "traceroute" mode (fault isolation), the echo request is sent to
the control plane at each transit LSR, and the control plane checks
that it is indeed a transit LSR for this P2MP MPLS LSP. The transit
LSR also returns information on an echo response that helps verify
the control plane against the data plane. That is, the information
is used by the ingress to check that the data plane forwarding
matches what is signaled by the control plane.
P2MP MPLS LSPs may have many egresses, and it is not necessarily the
intention of the initiator of the ping or traceroute operation to
collect information about the connectivity or path to all egresses.
Indeed, in the event of pinging all egresses of a large P2MP MPLS
LSP, it might be expected that a large number of echo responses would
arrive at the ingress independently but at approximately the same
time. Under some circumstances this might cause congestion at or
around the ingress LSR. Therefore, the procedures described in this
document provide a mechanism that allows the responders to randomly
delay (or jitter) their responses so that the chances of swamping the
ingress are reduced.
Further, the procedures in this document allow the initiator to limit
the scope of an LSP Ping echo request (ping or traceroute mode) to
one specific intended egress.
The scalability issues surrounding LSP Ping for P2MP MPLS LSPs may be
addressed by other mechanisms such as [MCAST-CV] that utilise the LSP
Ping procedures in this document to provide bootstrapping mechanisms
as described in Section 2.3.
LSP Ping can be used to periodically ping a P2MP MPLS LSP to ensure
connectivity to any or all of the egresses. If the ping fails,
the operator or an automated process can then initiate a traceroute
to determine where the fault is located within the network. A
traceroute may also be used periodically to verify that data plane
forwarding matches the control plane state; however, this places an
increased burden on transit LSRs and should be used infrequently and
with caution.
2.3 Bootstrapping Other OAM Procedures Using LSP Ping
[MPLS-BFD] describes a process where LSP Ping [RFC4379] is used to
bootstrap the Bidirectional Forwarding Detection (BFD) mechanism
[BFD] for use to track the liveliness of an MPLS LSP. In particular
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BFD can be used to detect a data plane failure in the forwarding
path of an MPLS LSP.
Requirements for MPLS P2MP LSPs extend to hundreds or even thousands
of endpoints. If a protocol required explicit acknowledgments to
each probe for connectivity verification, the response load at the
root would be overwhelming.
A more scalable approach to monitoring P2MP LSP connectivity is
desribed in [MCAST-CV]. It relies on using the MPLS echo request and
echo response messages of LSP Ping [RFC4379] to bootstrap the
monitoring mechanism in a manner similar to [MPLS-BFD]. The actual
monitoring is done using a separate process defined in [MCAST-CV].
Note that while the approach described in [MCAST-CV] was developed in
response to the multicast scalability problem, it can be applied to
P2P LSPs as well.
3. Operation of LSP Ping for a P2MP LSP
This section describes how LSP Ping is applied to P2MP MPLS LSPs.
It covers the mechanisms and protocol fields applicable to both ping
mode and traceroute mode. It explains the responsibilities of the
initiator (ingress), transit LSRs, and receivers (egresses).
3.1. Identifying the LSP Under Test
3.1.1. Identifying a P2MP MPLS TE LSP
[RFC4379] defines how an MPLS TE LSP under test may be identified in
an echo request. A Target FEC Stack TLV is used to carry either an
RSVP IPv4 Session or an RSVP IPv6 Session sub-TLV.
In order to identify the P2MP MPLS TE LSP under test, the echo
request message MUST carry a Target FEC Stack TLV, and this MUST
carry exactly one of two new sub-TLVs: either an RSVP P2MP IPv4
Session sub-TLV or an RSVP P2MP IPv6 Session sub-TLV. These sub-TLVs
carry fields from the RSVP-TE P2MP Session and Sender-Template
objects [RFC4875] and so provide sufficient information to uniquely
identify the LSP.
The new sub-TLVs are assigned sub-type identifiers as follows, and
are described in the following sections.
Sub-Type # Length Value Field
---------- ------ -----------
TBD 20 RSVP P2MP IPv4 Session
TBD 56 RSVP P2MP IPv6 Session
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3.1.1.1. RSVP P2MP IPv4 Session Sub-TLV
The format of the RSVP P2MP IPv4 Session sub-TLV value field is
specified in the following figure. The value fields are taken from
the definitions of the P2MP IPv4 LSP Session Object and the P2MP
IPv4 Sender-Template Object in [RFC4875]. Note that the Sub-Group
ID of the Sender-Template is not required.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel sender address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.1.1.2. RSVP P2MP IPv6 Session Sub-TLV
The format of the RSVP P2MP IPv6 Session sub-TLV value field is
specified in the following figure. The value fields are taken from
the definitions of the P2MP IPv6 LSP Session Object, and the
P2MP IPv6 Sender-Template Object in [RFC4875]. Note that the
Sub-Group ID of the Sender-Template is not required.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| P2MP ID |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Extended Tunnel ID |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 tunnel sender address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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3.1.2. Identifying a Multicast LDP LSP
[RFC4379] defines how a P2P LDP LSP under test may be identified in
an echo request. A Target FEC Stack TLV is used to carry one or more
sub-TLVs (for example, an IPv4 Prefix FEC sub-TLV) that identify the
LSP.
In order to identify a multicast LDP LSP under test, the echo request
message MUST carry a Target FEC Stack TLV, and this MUST carry
exactly one new sub-TLV: the Multicast LDP FEC Stack sub-TLV. This
sub-TLV uses fields from the multicast LDP messages [P2MP-LDP] and so
provides sufficient information to uniquely identify the LSP.
The new sub-TLV is assigned a sub-type identifier as follows, and
is described in the following section.
Sub-Type # Length Value Field
---------- ------ -----------
TBD Variable Multicast LDP FEC Stack
3.1.2.1. Multicast LDP FEC Stack Sub-TLV
The format of the Multicast LDP FEC Stack sub-TLV is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | Address Length| Root LSR Addr |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Root LSR Address (Cont.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Length | Opaque Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Family
A two octet quantity containing a value from ADDRESS FAMILY
NUMBERS in [IANA-PORT] that encodes the address family for the
Root LSR Address.
Address Length
The length of the Root LSR Address in octets.
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Root LSR Address
An address of the LSR at the root of the P2MP LSP encoded
according to the Address Family field.
Opaque Length
The length of the Opaque Value, in octets.
Opaque Value
An opaque value elements of which uniquely identifies the P2MP LSP
in the context of the Root LSR.
If the Address Family is IPv4, the Address Length MUST be 4. If the
Address Family is IPv6, the Address Length MUST be 16. No other
Address Family values are defined at present.
3.2. Ping Mode Operation
3.2.1. Controlling Responses to LSP Pings
As described in Section 2.2, it may be desirable to restrict the
operation of LSP Ping to a single egress. Since echo requests are
forwarded through the data plane without interception by the control
plane (compare with traceroute mode), there is no facility to limit
the propagation of echo requests, and they will automatically be
forwarded to all (reachable) egresses.
However, the intended egress under test can be identified by the
inclusion of a P2MP Egress Identifier TLV containing an IPv4 P2MP
Egress Identifier sub-TLV or an IPv6 P2MP Egress Identifier sub-TLV.
The P2MP Egress Identifier TLV SHOULD contain precisely one sub-TLV.
If the TLV contains no sub-TLVs it SHOULD be processed as if the
whole TLV were absent (causing all egresses to respond as described
below). If the TLV contains more than one sub-TLV, the first MUST be
precessed as described in this document, and subsequent sub-TLVs
SHOULD be ignored.
An initiator may indicate that it wishes all egresses to respond to
an echo request by omitting the P2MP Egress Identifier TLV.
Note that the ingress of a multicast LDP LSP will not know the
identities of the egresses of the LSP except by some external means
such as running P2MP LSP Ping to all egresses.
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3.2.2. Ping Mode Egress Procedures
An egress LSR is RECOMMENDED to rate limit its receipt of echo
request messages as described in [RFC4379]. After rate limiting, an
egress LSR that receives an echo request carrying an RSVP P2MP IPv4
Session sub-TLV, an RSVP P2MP IPv6 Session sub-TLV, or a Multicast
LDP FEC Stack sub-TLV MUST determine whether it is an intended egress
of the P2MP LSP in question by checking with the control plane. If it
is not supposed to be an egress, it MUST respond according to the
setting of the Response Type field in the echo message following the
rules defined in [RFC4379].
If the egress LSR that receives an echo request and allows it through
its rate limiting is an intended egress of the P2MP LSP, the LSR MUST
check to see whether it is an intended Ping recipient. If a P2MP
Egress Identifier TLV is present and contains an address that
indicates any address that is local to the LSR, the LSR MUST respond
according to the setting of the Response Type field in the echo
message following the rules defined in [RFC4379]. If the P2MP Egress
Identifier TLV is present, but does not identify the egress LSR, it
MUST NOT respond to the echo request. If the P2MP Egress Identifier
TLV is not present (or, in the error case, is present but does not
contain any sub-TLVs), but the egress LSR that received the echo
request is an intended egress of the LSP, the LSR MUST respond
according to the setting of the Response Type field in the echo
message following the rules defined in [RFC4379].
3.2.3. Jittered Responses
The initiator (ingress) of a ping request MAY request the responding
egress to introduce a random delay (or jitter) before sending the
response. The randomness of the delay allows the responses from
multiple egresses to be spread over a time period. Thus this
technique is particularly relevant when the entire LSP tree is being
pinged since it helps prevent the ingress (or nearby routers) from
being swamped by responses, or from discarding responses due to rate
limits that have been applied.
It is desirable for the ingress to be able to control the bounds
within which the egress delays the response. If the tree size is
small, only a small amount of jitter is required, but if the tree is
large, greater jitter is needed. The ingress informs the egresses of
the jitter bound by supplying a value in a new TLV (the Echo Jitter
TLV) carried on the echo request message. If this TLV is present,
the responding egress MUST delay sending a response for a random
amount of time between zero seconds and the value indicated in the
TLV. If the TLV is absent, the responding egress SHOULD NOT introduce
any additional delay in responding to the echo request.
LSP ping SHOULD NOT be used to attempt to measure the round-trip
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time for data delivery. This is because the LSPs are unidirectional,
and the echo response is often sent back through the control plane.
The timestamp fields in the echo request/response MAY be used to
deduce some information about delivery times and particularly the
variance in delivery times.
The use of echo jittering does not change the processes for gaining
information, but note that the responding egress MUST set the value
in the Timestamp Received fields before applying any delay.
It is RECOMMENDED that echo response jittering is not used except in
the case of P2MP LSPs. If the Echo Jitter TLV is present in an echo
request for any other type of TLV, the responding egress MAY apply
the jitter behavior described here.
3.2.4. P2MP Egress Identifier TLV and Sub-TLVs
A new TLV is defined for inclusion in the Echo request message.
The P2MP Egress Identifier TLV is assigned the TLV type value TBD and
is encoded 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = TBD (P2MP Egress ID TLV)| Length = Variable |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub-TLVs ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-TLVs:
Zero, one or more sub-TLVs as defined below.
If no sub-TLVs are present, the TLV MUST be processed as if it
were absent. If more than one sub-TLV is present the first MUST
be processed as described in this document, and subsequent
sub-TLVs SHOULD be ignored.
The P2MP Egress Identifier TLV only has meaning on an echo request
message. If present on an echo response message, it SHOULD be
ignored.
Two sub-TLVs are defined for inclusion in the P2MP Egress Identifier
TLV carried on the echo request message. These are:
Sub-Type # Length Value Field
---------- ------ -----------
1 4 IPv4 P2MP Egress Identifier
2 16 IPv6 P2MP Egress Identifier
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The value of an IPv4 P2MP Egress Identifier consists of four octets
of an IPv4 address. The IPv4 address is in network byte order.
The value of an IPv6 P2MP Egress Identifier consists of sixteen
octets of an IPv6 address. The IPv6 address is in network byte order.
3.2.5. Echo Jitter TLV
A new TLV is defined for inclusion in the Echo request message.
The Echo Jitter TLV is assigned the TLV type value TBD and is encoded
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD (Jitter TLV) | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Jitter time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jitter time:
This field specifies the upper bound of the jitter period that
should be applied by a responding egress to determine how long
to wait before sending an echo response. An egress SHOULD wait
a random amount of time between zero seconds and the value
specified in this field.
Jitter time is specified in milliseconds.
The Echo Jitter TLV only has meaning on an echo request message. If
present on an echo response message, it SHOULD be ignored.
3.3. Traceroute Mode Operation
The traceroute mode of operation is described in [RFC4379]. Like
other traceroute operations, it relies on the expiration of the TTL
of the packet that carries the echo request. Echo requests may
include a Downstream Mapping TLV, and when the TTL expires the echo
request is passed to the control plane on the transit LSR which
responds according to the Response Type in the message. A responding
LSR fills in the fields of the Downstream Mapping TLV to indicate the
downstream interfaces and labels used by the reported LSP from the
responding LSR. In this way, by successively sending out echo
requests with increasing TTLs, the ingress may gain a picture of the
path and resources used by an LSP up to the point of failure when no
response is received, or an error response is generated by an LSR
where the control plane does not expect to be handling the LSP.
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This mode of operation is equally applicable to P2MP MPLS TE LSPs
as described in the following sections.
The traceroute mode can be applied to all destinations of the P2MP
tree just as in the ping mode. In the case of P2MP MPLS TE LSPs, the
traceroute mode can also be applied to individual destinations
identified by the presence of a P2MP Egress Identifier TLV. However,
since a transit LSR of a multicast LDP LSP is unable to determine
whether it lies on the path to any one destination, the traceroute
mode limited to specific egresses of such an LSP MUST NOT be used.
In the absence of a P2MP Egress Identifier TLV, the echo request is
asking for traceroute information applicable to all egresses.
The echo response jitter technique described for the ping mode is
equally applicable to the traceroute mode and is not additionally
described in the procedures below.
3.3.1. Traceroute Responses at Non-Branch Nodes
When the TTL for the MPLS packet carrying an echo request expires the
packet MUST be passed to the control plane as specified in [RFC4379].
If the LSP under test is a multicast LDP LSP and if the echo request
carries a P2MP Egress Identifier TLV the LSR MUST treat the echo
request as malformed and MUST process it according to the rules
specified in [RFC4379].
Otherwise, the LSR MUST NOT return an echo response unless the
responding LSR lies on the path of the P2MP LSP to the egress
identified by the P2MP Egress Identifier TLV carried on the request,
or if no such sub-TLV is present.
If sent, the echo response MUST identifiy the next hop of the path of
the LSP in the data plane by including a Downstream Mapping TLV as
described in [RFC4379].
3.3.1.1. Correlating Traceroute Responses
When traceroute is being simultaneously applied to multiple egresses,
it is important that the ingress should be able to correlate the echo
responses with the branches in the P2MP tree. Without this
information the ingress will be unable to determine the correct
ordering of transit nodes. One possibility is for the ingress to poll
the path to each egress in turn, but this may be inefficient,
undesirable, or (in the case of multicast LDP LSPs) illegal.
The Downstream Mapping TLV that MUST be included in the echo response
indicates the next hop from each responding LSR, and this information
supplied by a non-branch LSR can be pieced together by the ingress to
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reconstruct the P2MP tree although it may be necessary to refer to
the routing information distributed by the IGP to correlate next hop
addresses and LSR reporting addresses in subsequent echo responses.
In order to facilitate more easy correlation of echo responses, the
Downstream Mapping TLV can also contain Multipath Information as
described in [RFC4379] to identify to which egress/egresses the echo
response applies, and indicates. This information:
- MUST NOT be present for multicast LDP LSPs
- SHOULD be present for P2MP MPLS TE LSPs when the echo request
applies to all egresses
- is RECCOMMENDED to be present for P2MP MPLS TE LSPs when the echo
request is limited to a single egress.
The format of the information in the Downstream Mapping TLV for
P2MP MPLS LSPs is described in section 3.3.5 and 3.3.6.
3.3.2. Traceroute Responses at Branch Nodes
A branch node may need to identify more than one downstream interface
in a traceroute echo response if some of the egresses that are being
traced lie on different branches. This will always be the case for
any branch node if all egresses are being traced.
[RFC4379] describes how multiple Downstream Mapping TLVs should be
included in an echo response, each identifying exactly one downstream
interface that is applicable to the LSP.
A branch node MUST follow the procedures described in Section 3.3.1
to determine whether it should respond to an echo request. The branch
node MUST add a Downstream Mapping TLV to the echo response for each
outgoing branch that it reports, but it MUST NOT report branches that
do not lie on the path to one of the destinations being traced. Thus
a branch node may sometimes only need to respond with a single
Downstream Mapping TLV, for example, consider the case where the
traceroute is directed to only a single egress node. Therefore,
the presence of only one Downstream Mapping TLV in an echo response
does not guarantee that the reporting LSR is not a branch node.
To report on the fact that an LSR is a branch node for the P2MP MPLS
LSP a new B-flag is added to the Downstream Mapping TLV. The flag is
set to zero to indicate that the reporting LSR is not a branch for
this LSP, and is set to one to indicate that it is a branch. The flag
is placed in the fourth byte of the TLV that was previously reserved.
The format of the information in the Downstream Mapping TLV for
P2MP MPLS LSPs is described in section 3.3.5 and 3.3.6.
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3.3.2.1. Correlating Traceroute Responses
Just as with non-branches, it is important that the echo responses
from branch nodes provide correlation information that will allow the
ingress to work out to which branch of the LSP the response applies.
The P2MP tree can be determined by the ingress using the identity of
the reporting node and the next hop information from the previous
echo response, just as with echo responses from non-branch nodes.
As with non-branch nodes, in order to facilitate more easy
correlation of echo responses, the Downstream Mapping TLV can also
contain Multipath Information as described in [RFC4379] to identify
to which egress/egresses the echo response applies, and indicates.
This information:
- MUST NOT be present for multicast LDP LSPs
- SHOULD be present for P2MP MPLS TE LSPs when the echo request
applies to all egresses
- is RECCOMMENDED to be present for P2MP MPLS TE LSPs when the echo
request is limited to a single egress.
The format of the information in the Downstream Mapping TLV for
P2MP MPLS LSPs is described in section 3.3.5 and 3.3.6.
3.3.3. Traceroute Responses at Bud Nodes
Some nodes on a P2MP MPLS LSP may be egresses, but also have
downstream LSRs. Such LSRs are known as bud nodes [RFC4461].
A bud node MUST respond to a traceroute echo request just as a branch
node would, but it MUST also indicates to the ingress that it is an
egress in its own right. This is achieved through the use of a new
E-flag in the Downstream Mapping TLV that indicates that the
reporting LSR is not a bud for this LSP (cleared to zero) or is a bud
(set to one). A normal egress MUST NOT set this flag.
The flag is placed in the fourth byte of the TLV that was previously
reserved.
3.3.4. Non-Response to Traceroute Echo Requests
The nature of P2MP MPLS TE LSPs in the data plane means that
traceroute echo requests may be delivered to the control plane of
LSRs that must not reply to the request because, although they lie
on the P2MP tree, they do not lie on the path to the egress that is
being traced.
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Thus, an LSR on a P2MP MPLS LSP MUST NOT respond to an echo request
when the TTL has expired if any of the following applies:
- The Reply Type indicates that no reply is required
- There is a P2MP Egress Identifier TLV present on the echo request
(which means that the LSP is a P2MP MPLS TE LSP), but the address
does not identify an egress that is reached through this LSR for
this particular P2MP MPLS LSP.
3.3.5. Modifications to the Downstream Mapping TLV
A new B-flag is added to the Downstream Mapping TLV to indicate that
the reporting LSR is not a branch for this LSP (cleared to zero) or
is a branch (set to one).
A new E-flag is added to the Downstream Mapping TLV to indicate that
the reporting LSR is not a bud node for this LSP (cleared to zero) or
is a bud node (set to one).
The flags are placed in the fourth byte of the TLV that was
previously reserved as shown below. All other fields are unchanged
from their definitions in [RFC4379] except for the additional
information that can be carried in the Multipath Information (see
Section 3.3.6).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MTU | Address Type | Reserved |E|B|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Interface Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hash Key Type | Depth Limit | Multipath Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. (Multipath Information) .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Label | Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Downstream Label | Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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3.3.6. Additions to Downstream Mapping Multipath Information
A new value for the Multipath Type is defined to indicate that the
reported Multipath Information applies to a P2MP MPLS TE LSP and
may contain a list of egress identifiers that indicate the egress
nodes that can be reached through the reported interface. This
Multipath Type MUST NOT be used for a multicast LDP LSP.
Type # Address Type Multipath Information
--- ---------------- ---------------------
TBD P2MP egresses List of P2MP egresses
Note that a list of egresses may include IPv4 and IPv6 identifiers
since these may be mixed in the P2MP MPLS TE LSP.
The Multipath Length field continues to identify the length of the
Multipath Information just as in [RFC4379] (that is, not including
the downstream labels), and the downstream label (or potential
stack thereof) is also handled just as in [RFC4379]. The format
of the Multipath Information for a Multipath Type of P2MP Egresses
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | Egress Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (continued) | :
+-+-+-+-+-+-+-+-+ :
: Further Address Types and Egress Addresses :
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
This field indicates whether the egress address that follows is
an IPv4 or IPv6 address, and so implicitly encodes the length of
the address.
Two values are defined and mirror the values used in the Address
Type field of the Downstream Mapping TLV itself.
Type # Address Type
------ ------------
1 IPv4
3 IPv6
Egress Address
An egress of this P2MP MPLS TE LSP that is reached through the
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interface indicated by the Downstream Mapping TLV and for which
the traceroute echo request was enquiring.
4. Operation of LSP Ping for Bootstrapping Other OAM Mechanisms
Bootstrapping of other OAM procedures can be achieved using the
MPLS Echo Request/Response messages. The LSP(s) under test are
identified using the RSVP P2MP IPv4 or IPv6 Session sub-TLVs
(see Section 3.1.1) or the Multicast LDP FEC Stack sub-TLV
(see Section 3.1.2).
Other sub-TLVs may be defined in other specifications to indicate
the OAM procedures being bootstrapped, and to describe the bootstrap
parameters. Further details of the bootstrapping processes and the
bootstrapped OAM processes are described in other documents. For
example, see [MPLS-BFD] and [MCAST-CV].
5. Non-compliant Routers
If an egress for a P2MP LSP does not support MPLS LSP ping, then no
reply will be sent, resulting in a "false negative" result. There is
no protection for this situation, and operators may wish to ensure
that end points for P2MP LSPs are all equally capable of supporting
this function. Alternatively, the traceroute option can be used to
verify the LSP nearly all the way to the egress, leaving the final
hop to be verified manually.
If, in "traceroute" mode, a transit LSR does not support LSP ping,
then no reply will be forthcoming from that LSR for some TTL, say n.
The LSR originating the echo request SHOULD continue to send echo
requests with TTL=n+1, n+2, ..., n+k in the hope that some transit
LSR further downstream may support MPLS echo requests and reply. In
such a case, the echo request for TTL > n MUST NOT have Downstream
Mapping TLVs, until a reply is received with a Downstream Mapping.
Note that the settings of the new bit flags in the Downstream Mapping
TLV are such that a legacy LSR would return them with value zero
which most closely matches the likely default behavior of a legacy
LSR.
6. OAM Considerations
The procedures in this document provide OAM functions for P2MP MPLS
LSPs and may be used to enable bootstrapping of other OAM procedures.
In order to be fully operational several considerations must be made.
- Scaling concerns dictate that only cautious use of LSP Ping should
be made. In particular, sending an LSP Ping to all egresses of a
P2MP MPLS LSP could result in congestion at or near the ingress
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when the responses arrive.
Further, incautious use of timers to generate LSP Ping echo
requests either in ping mode or especially in traceroute may lead
to significant degradation of network performance.
- Management interfaces should allow an operator full control over
the operation of LSP Ping. In particular, it SHOULD provide the
ability to limit the scope of an LSP Ping echo request for a P2MP
MPLS LSP to a single egress.
Such an interface SHOULD also provide the ability to disable all
active LSP Ping operations to provide a quick escape if the network
becomes congested.
- A MIB module is required for the control and management of LSP Ping
operations, and to enable the reported information to be inspected.
There is no reason to believe this should not be a simple extension
of the LSP Ping MIB module used for P2P LSPs.
7. IANA Considerations
7.1. New Sub-TLV Types
Three new sub-TLV types are defined for inclusion within the LSP Ping
[RFC4379] Target FEC Stack TLV (TLV type 1).
IANA is requested to assign sub-type values to the following
sub-TLVs from the Multiprotocol Label Switching Architecture (MPLS)
Label Switched Paths (LSPs) Parameters - TLVs registry.
RSVP P2MP IPv4 Session (see Section 3.1.1)
RSVP P2MP IPv6 Session (see Section 3.1.1)
Multicast LDP FEC Stack (see Section 3.1.2)
7.2. New Multipath Type
Section 3.3 of [RFC4379] defines a set of values for the LSP Ping
Multipath Type. These values are currently not tracked by IANA.
A new value for the LSP Ping Multipath Type is defined in Section
3.3.6 of this document to indicate that the reported Multipath
Information applies to a P2MP MPLS TE LSP.
IANA is requested to create a new registry as follows:
Multiprotocol Label Switching Architecture (MPLS) Label Switched
Paths (LSPs) - Multipath Types
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Key Type Multipath Information
--- ---------------- ---------------------
0 no multipath Empty (Multipath Length = 0) [RFC4379]
2 IP address IP addresses [RFC4379]
4 IP address range low/high address pairs [RFC4379]
8 Bit-masked IP IP address prefix and bit mask [RFC4379]
address set
9 Bit-masked label set Label prefix and bit mask [RFC4379]
xx P2MP egress IP List of P2MP egresses [thisDoc]
addresses
A suggested value of xx is TBD by the MPLS Working Group.
New values from this registry are to be assigned only by Standards
Action.
7.3. New TLVs
Two new LSP Ping TLV types are defined for inclusion in LSP Ping
messages.
IANA is reuqested to assign a new value from the Multiprotocol Label
Switching Architecture (MPLS) Label Switched Paths (LSPs) Parameters
- TLVs registry as follows using a Standards Action value.
P2MP Egress Identifier TLV (see Section 3.2.4)
Two sub-TLVs are defined
- Type 1: IPv4 P2MP Egress Identifier (see Section 3.2.4)
- Type 2: IPv6 P2MP Egress Identifier (see Section 3.2.4)
Echo Jitter TLV (see Section 3.2.5)
8. Security Considerations
This document does not introduce security concerns over and above
those described in [RFC4379]. Note that because of the scalability
implications of many egresses to P2MP MPLS LSPs, there is a
stronger concern to regulate the LSP Ping traffic passed to the
control plane by the use of a rate limiter applied to the LSP Ping
well-known UDP port. Note that this rate limiting might lead to
false positives.
9. Acknowledgements
The authors would like to acknowledge the authors of [RFC4379] for
their work which is substantially re-used in this document. Also
thanks to the members of the MBONED working group for their review
of this material, to Daniel King for his review, and to Yakov Rekhter
for useful discussions.
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The authors would like to thank Vanson Lim, Danny Prairie, Reshad
Rahman, and Ben Niven-Jenkins for their comments and suggestions.
10. Intellectual Property Considerations
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
11. 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 Swallow, G., "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
12. Informative References
[RFC792] Postel, J., "Internet Control Message Protocol", RFC 792.
[RFC4461] Yasukawa, S., "Signaling Requirements for Point to
Multipoint Traffic Engineered Multiprotocol Label
Switching (MPLS) Label Switched Paths (LSPs)",
RFC 4461, April 2006.
[RFC4687] Yasukawa, S., Farrel, A., King, D., and Nadeau, T.,
"Operations and Management (OAM) Requirements for
Point-to-Multipoint MPLS Networks", RFC 4687, September
2006.
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[RFC4875] Aggarwal, R., Papadimitriou, D., and Yasukawa, S.,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[P2MP-LDP-REQ] J.-L. Le Roux, et al., "Requirements for
point-to-multipoint extensions to the Label Distribution
Protocol", draft-ietf-mpls-mp-ldp-reqs, work in progress.
[P2MP-LDP] Minei, I., and Wijnands, I., "Label Distribution Protocol
Extensions for Point-to-Multipoint and
Multipoint-to-Multipoint Label Switched Paths",
draft-ietf-mpls-ldp-p2mp, work in progress.
[MCAST-CV] Swallow, G., and Nadeau, T., "Connectivity Verification
for Multicast Label Switched Paths",
draft-swallow-mpls-mcast-cv, work in progress.
[BFD] Katz, D., and Ward, D., "Bidirectional Forwarding
Detection", draft-ietf-bfd-base, work in progress.
[MPLS-BFD] Aggarwal, R., Kompella, K., Nadeau, T., and Swallow, G.,
"BFD For MPLS LSPs", draft-ietf-bfd-mpls, work in
progress.
[IANA-PORT] IANA Assigned Port Numbers, http://www.iana.org
13. Authors' Addresses
Seisho Yasukawa
NTT Corporation
(R&D Strategy Department)
3-1, Otemachi 2-Chome Chiyodaku, Tokyo 100-8116 Japan
Phone: +81 3 5205 5341
Email: s.yasukawa@hco.ntt.co.jp
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Zafar Ali
Cisco Systems Inc.
2000 Innovation Drive
Kanata, ON, K2K 3E8, Canada.
Phone: 613-889-6158
Email: zali@cisco.com
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Bill Fenner
AT&T Labs -- Research
75 Willow Rd.
Menlo Park, CA 94025
United States
Email: fenner@research.att.com
George Swallow
Cisco Systems, Inc.
1414 Massachusetts Ave
Boxborough, MA 01719
Email: swallow@cisco.com
Thomas D. Nadeau
British Telecom
BT Centre
81 Newgate Street
EC1A 7AJ
London
Email: tom.nadeau@bt.com
14. Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Yasukawa and Farrel [Page 25]
