Network Working Group Seisho Yasukawa
IETF Internet Draft NTT
Proposed Status: Informational
Expires: April 2005
Adrian Farrel
Olddog Consulting
Zafar Ali
Cisco Systems
October 2004
Detecting Data Plane Failures in Point-to-Multipoint MPLS Traffic
Engineering - Extensions to LSP Ping
draft-yasukawa-mpls-p2mp-lsp-ping-00.txt
Status of this Memo
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Yasukawa, Farrel and Ali. [Page 1]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
Abstract
Recent proposals have extended the scope of Multi-Protocol Label
Switching (MPLS) traffic engineered Label Switched Paths (TE LSPs)
to encompass point-to-multipoint (P2MP) TE 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 recognized and has led to the development of techniques
for fault detection and isolation commonly referred to as "LSP Ping"
[LSP-PING].
This documents does not replace any of the mechanism of LSP Ping, but
clarifies their applicability to P2MP MPLS TE LSPs, and extends the
techniques and mechanisms of LSP Ping to the P2MP TE
environment.
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].
Yasukawa, Farrel and Ali. [Page 2]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
Contents
1. Introduction .................................................. 04
1.1 Design Considerations ..................................... 04
2. Notes on Motivation ........................................... 05
2.1. Basic Motivations for LSP Ping ........................... 05
2.2. Motivations for LSP Ping for P2MP TE LSPs ................ 05
3. Operation of LSP Ping for a P2MP TE LSP ....................... 07
3.1. Identifying the LSP Under Test ........................... 07
3.1.1. RSVP P2MP IPv4 Session Sub-TLV ......................... 07
3.1.2. RSVP P2MP IPv6 Session Sub-TLV ......................... 08
3.2. Ping Mode Operation ...................................... 09
3.2.1. Controlling Responses to LSP Pings ..................... 09
3.2.2. P2MP Egress Identifier sub-TLVs ........................ 10
3.3. Traceroute Mode Operation ................................ 10
3.3.1. Traceroute Responses at Non-Branch Nodes ............... 11
3.3.2. Traceroute Responses at Branch Nodes .................. 11
3.3.3. Traceroute Responses at Bud Nodes ...................... 12
3.3.4. Non-Response to Traceroute Echo Requests ............... 12
3.3.5. Modifications to the Downstream Mapping TLV ............ 13
3.3.6. Additions to Downstream Mapping Multipath Information .. 14
4. OAM Considerations ............................................ 15
5. IANA Considerations ........................................... 16
5.1. New Sub TLV Types ........................................ 16
6. Security Considerations ....................................... 16
7. Acknowledgements .............................................. 16
8. Intellectual Property Considerations .......................... 16
9. Normative References .......................................... 17
10. Informational References ..................................... 17
11. Authors' Addresses ........................................... 18
12. Full Copyright Statement ..................................... 18
Yasukawa, Farrel and Ali. [Page 3]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
1. Introduction
Simple and efficient mechanisms that can be used to detect data plane
failures in point-to-point MPLS LSP are described in [LSP-PING]. 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 reply channels for echo request messages
as described in [LSP-PING] enables more robust fault isolation. This
collection of mechanisms is commonly referred to as "LSP Ping".
The requirement for Point-to-multipoint traffic engineered MPLS LSPs
is introduced in [P2MP-REQ]. [P2MP-RSVP] specifies a signaling
solution for establishing P2MP MPLS TE LSPs. P2MP MPLS TE LSPs are at
least as vulnerable to data plane faults or to discrepancies between
the control and data planes as their P2P counterparts. LSP Ping
Mechanisms are, therefore, also desirable to detect such data plane
faults in P2MP MPLS TE LSPs.
This document extends the techniques described in [LSP-PING] in order
that they may be applied to P2MP MPLS TE LSPs. This document stresses
the reuse of existing LSP Ping mechanisms as such reuse simplifies
operations of the network.
1.1 Design Considerations
As mentioned earlier, an important consideration for designing LSP
Ping for P2MP MPLS TE LSPs is that every attempt is made to use or
extend existing mechanisms rather than invent new mechanisms.
As for P2P LSPs, a critical requirement is that the echo request
messages follow the same data path that normal MPLS packets would
traverse. However, it can be seen this notion needs to be extended
for P2MP MPLS TE 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 secondarily to verify the data plane against the control plane.
As pointed out in [LSP-PING], mechanisms to check the liveness,
function and consistency of the control plane are valuable, but such
mechanisms are not covered in this document.
As is described in [LSP-PING], 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.
Yasukawa, Farrel and Ali. [Page 4]
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2. Notes on Motivation
2.1. Basic Motivations for LSP Ping
The motivations listed in [LSP-PING] 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 would enable users to detect such traffic "black holes" or
misrouting within a reasonable period of time; and a mechanism to
isolate faults.
[LSP-PING] 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. [LSP-PING] specifies a "ping mode" and a "traceroute" mode
for testing MPLS LSPs.
The basic idea as expressed in [LSP-PING] 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. [LSP-PING] 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
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 thus should be used with caution.
Yasukawa, Farrel and Ali. [Page 5]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
2.2. Motivations for LSP Ping for P2MP TE LSPs
P2MP MPLS TE LSPs may be viewed as MPLS tunnels with a single ingress
and multiple egresses. MPLS packets inserted at the ingress are
delivered equally (barring faults) to all egresses. There is no
concept or applicability of an FEC in the context of a P2MP MPLS TE
LSP, just as there is no similar concept for point-to-point TE LSPs.
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 MPLS TE LSP actually end their MPLS path
on LSRs that are (intended) egresses for that LSP. The idea may be
extended to check selectively that such packets reach a specific
egress, or a particular group of egresses of the LSP.
This document proposes that this test is carried out 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 TE LSP that it is testing. The echo request is forwarded just as
any other packet using that LSP. 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 LSR, which then
verifies that it is indeed an egress (leaf) of the P2MP MPLS TE LSP.
An echo response message is sent by the 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 TE 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 TE 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 TE
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 the ability for the initiator to limit the scope of
an LSP Ping (ping or traceroute mode) to one or a limited list of the
intended egresses of the P2MP MPLS TE LSP.
Yasukawa, Farrel and Ali. [Page 6]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
LSP Ping can be used to periodically ping a P2MP MPLS TE 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.
3. Operation of LSP Ping for a P2MP TE LSP
This section describes how LSP Ping is applied to P2MP MPLS TE 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
[LSP-PING] 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 or an RSVP P2MP IPv6 Session sub-TLV. These sub-TLVs carry
the various fields from the RSVP-TE P2MP Session and Sender-Template
objects [P2MP-RSVP] 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
3.1.1. 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 [P2MP-RSVP]. Note that the Sub-Group
ID of the Sender-Template is not required.
Yasukawa, Farrel and Ali. [Page 7]
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel sender address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Must Be Zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.1.2. 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 [P2MP-RSVP]. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Yasukawa, Farrel and Ali. [Page 8]
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3.2. Ping Mode Operation
3.2.1. Controlling Responses to LSP Pings
As described above, 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 is identified in the FEC
Stack TLV by the inclusion of an IPv4 P2MP Egress Identifier sub-TLV
or an IPv6 P2MP Egress Identifier sub-TLV. Such TLVs MUST be placed
after the RSVP P2MP IPv4/6 Session sub-TLV.
An egress LSR that receives an echo request carrying an RSVP P2MP
IPv4/6 Session 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 [LSP-PING].
If the egress that receives an echo request is an intended egress,
the LSR can check to see whether it is an intended Ping recipient.
If the address included in the P2MP Egress Identifier sub-TLV
indicates any address that is local to the egress LSR it, MUST
respond according to the setting of the Response Type field in the
echo message following the rules defined in [LSP-PING]. If the
address in the P2MP Egress Identifier sub-TLV does not identify the
egress LSR, it MUST NOT respond to the echo request.
Multiple P2MP Egress Identifier sub-TLVs may appear in a list after
the RSVP P2MP IPv4/6 Session sub-TLV. In this case, each identifies a
single egress that is intended to reply to the echo request according
to the setting in the Reply Type field. An egress SHOULD consider
itself a target of the echo request if any of its local addresses
matches any of the specified egress identifiers.
An initiator may indicate that it wishes all egresses to respond to
an echo request by omitting all P2MP Egress Identifier sub-TLVs.
Yasukawa, Farrel and Ali. [Page 9]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
3.2.2. P2MP Egress Identifier sub-TLVs
Two new sub-TLVs are defined for inclusion in the Target FEC Stack
TLV (type 1) carried on the echo request message. These are:
Sub-Type # Length Value Field
---------- ------ -----------
(TBD) 4 IPv4 P2MP Egress Identifier
(TBD) 16 IPv6 P2MP Egress Identifier
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.
3.3. Traceroute Mode Operation
The traceroute mode of operation is described in [LSP-PING]. 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.
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 a single destination, a set of
destinations, or to all destinations of the P2MP tree just as in the
ping mode. That is, the IPv4/6 P2MP Egress Identifier sub-TLVs may
be used to identify one or more egresses for which traceroute
information is requested. In the absence of an IPv4/6 P2MP Egress
Identifier sub-TLV, the echo request is asking for traceroute
information applicable to all egresses.
Yasukawa, Farrel and Ali. [Page 10]
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3.3.1. Traceroute Responses at Non-Branch Nodes
When the TTL for the MPLS packet carrying an echo request expires and
the message is passed to the control plane, an echo response MUST
only be returned if the responding LSR lies on the path to one or
more of the egresses identified by the IPv4/6 P2MP Egress Identifiers
carried on the request, or if not such sub-TLV is present.
The echo response identifies the next hop of the path in the data
plane by including a Downstream Mapping TLV as described in
[LSP-PING].
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 or
undesirable. Therefore, the echo response contains additional
information in the Multipath Information field of the Downstream
Mapping TLV that identifies to which egress/egresses the echo
response applies. This information MUST be present when the echo
request applies to more than one egress, and is RECOMMENDED to be
present even when the echo request is limited to a single egress.
The format of the information in the Downstream Mapping TLV for
MPLS P2MP TE 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 would always be the case for
any branch node if all egresses are being traced.
[LSP-PING] 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.
Just as with non-branches, it is important that the echo responses
provide correlation information that will allow the ingress to work
out to which branch of the LSP the response applies. Further, when
multiple downstream interfaces are identified, it is necessary to
indicate which egresses are reached through which branches. This is
achieved exactly as for non-branch nodes: that is, by including a
list of egresses as part of the Multipath Information field of the
appropriate Downstream Mapping TLV.
Yasukawa, Farrel and Ali. [Page 11]
Internet Draft draft-yasukawa-mpls-p2mp-lsp-ping-00.txt October 2004
Note also that a branch node may sometimes only need to respond with
a single Downstream Mapping TLV. Consider the case where the
traceroute is directed to only a single egress node, or where a
subset of the egresses are being traced, but where all of them are
reached through the same branch. 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 MPLS P2MP
TE LSP, a new B-flag is added to the Downstream Mapping TLV to
indicate that the reporting LSR is not a branch for this LSP (set to
zero) or is a branch (set to one). The flag is placed in the fourth
byte of the TLV that was previous reserved.
The format of the information in the Downstream Mapping TLV for
MPLS P2MP TE LSPs is described in section 3.3.5 and 3.3.6.
3.3.3. Traceroute Responses at Bud Nodes
Some nodes on an MPLS P2MP TE LSP may be egresses, but also have
downstream LSRs. Such LSRs are known as bud nodes.
A bud node will respond to a traceroute echo request just as a branch
node would, but it is also important that it 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 (set to zero) or is a bud
(set to one). A normal egress is not required to set this flag.
The flag is placed in the fourth byte of the TLV that was previous
reserved.
3.3.4. Non-Response to Traceroute Echo Requests
The nature of MPLS P2MP TE LSPs in the data plane mean 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 paths to the egresses that
are being traced.
Thus, an LSR on a P2MP MPLS TE LSP MUST NOT respond to an echo
request for which the TTL has expired if any of the following
applies:
- The Reply Type indicates that no reply is required
- There is one or more IPv4/6 P2MP Egress Identifiers present on the
echo request and none of the addresses identifies an egress that is
reached, for this particular MPLS P2MP TE LSP, through this LSR.
Yasukawa, Farrel and Ali. [Page 12]
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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 (set 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 (set 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 [LSP-PING] except for the additional
information that can be carried in the Multipath Information.
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 | Resvd |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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Yasukawa, Farrel and Ali. [Page 13]
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3.3.6. Additions to Downstream Mapping Multipath Information
A new value for the Hash Key Type is defined to indicate that the
reported Multipath Information applies to an MPLS P2MP TE LSP and
may contain a list of egress identifiers that indicate the egress
nodes that can be reached through the reported interface.
Key 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 MPLS P2MP TE LSP.
The Multipath Length field continues to identify the length of the
Multipath Information just as in [LSP-PING] (that is not including
the downstream labels), and the downstream label (or potential
stack thereof) is also handled just as in [LSP-PING]. The format
of the Multipath Information for a Hash Key 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
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Egress Address
An egress of this MPLS P2MP TE LSP that is reached through the
interface indicated by the Downstream Mapping TLV and for which
the traceroute echo request was enquiring.
4. OAM Considerations
This draft clearly facilitates OAM procedures for P2MP MPLS TE LSPs.
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 TE LSP could result in congestion at or near the ingress
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 TE 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.
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5. IANA Considerations
5.1. New Sub TLV Types
Four new sub-TLV types are defined for inclusion within the Target
FEC Stack TLV (TLV type 1).
IANA is requested to assign sub-type values to the following
sub-TLVs.
RSVP P2MP IPv4 Session (see section 3.1)
RSVP P2MP IPv6 Session (see section 3.1)
IPv4 P2MP Egress Identifier (see section 3.2.2)
IPv6 P2MP Egress Identifier (see section 3.2.2)
6. Security Considerations
This document does not introduce security concerns over and above
those described in [LSP-PING]. Note that because of the scalability
implications of many egresses to P2MP MPLS TE 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.
7. Acknowledgements
The authors would like to acknowledge the authors of [LSP-PING] for
their work which is substantially re-used in this document.
8. 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.
Yasukawa, Farrel and Ali. [Page 16]
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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.
9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3667] Bradner, S., "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004.
[RFC3668] Bradner, S., Ed., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3668, February 2004.
[LSP-PING] Kompella, K., and Swallow, G., (Editors), "Detecting
MPLS Data Plane Failures", draft-ietf-mpls-lsp-ping,
work in progress.
10. Informational References
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP: 26, RFC 2434,
October 1998.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3552] Rescorla E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP: 72, RFC 3552,
July 2003.
[RFC792] Postel, J., "Internet Control Message Protocol", RFC 792.
[P2MP-REQ] S. Yasukawa, et. al., "Requirements for Point to
Multipoint Traffic Engineered MPLS LSPs",
draft-ietf-mpls-p2mp-requirement, work in progress.
[P2MP-RSVP] R. Aggarwal, et. al., "Extensions to RSVP-TE for Point to
Multipoint TE LSPs", draft-raggarwa-mpls-rsvp-te-p2mp,
work in progress.
Yasukawa, Farrel and Ali. [Page 17]
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11. Authors' Addresses
Seisho Yasukawa
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585,
Japan
Phone: +81 422 59 4769
Email: yasukawa.seisho@lab.ntt.co.jp
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Zafar Ali
Cisco Systems Inc.
100 South Main St. #200
Ann Arbor, MI 48104, USA.
Phone: (734) 276-2459
Email: zali@cisco.com
12. Full Copyright Statement
Copyright (C) The Internet Society (2004). 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 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, Farrel and Ali. [Page 18]