Network Working Group George Swallow
Internet Draft Cisco Systems, Inc.
Category: Standards Track
Expiration Date: May 2008
Vanson Lim
Cisco Systems, Inc.
November 2007
Proxy LSP Ping
draft-ietf-mpls-remote-lsp-ping-01.txt
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Abstract
This document defines a means of remotely initiating Multiprocal
Label Switched Protocol Pings on Label Switched Paths. A proxy
ping request is sent to any Label Switching Routers along a Label
Switched Path. The primary motivations for this facility are
first to limit the number of messages and related processing when
using LSP Ping in large Point-to-Multipoint LSPs, and second to
enable leaf to root tracing.
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Contents
1 Introduction .............................................. 3
1.1 Conventions ............................................... 3
2 Proxy Ping Overview ....................................... 4
3 Remote Echo / Reply Pprocedures ........................... 5
3.1 Procedures for the initiator .............................. 5
3.2 Procedures for the proxy LSR .............................. 6
3.2.1 Sending an MPLS proxy ping reply .......................... 7
3.2.2 Sending the MPLS echo requests ............................ 7
4 Proxy Ping Request / Reply Messages ....................... 8
4.1 Proxy Ping Request / Reply Message formats ................ 9
4.2 Proxy Ping Request Message contents ....................... 10
4.3 Proxy Ping Reply Message Contents ......................... 10
5 Object formats ............................................ 11
5.1 Proxy Echo Parameters Object .............................. 11
5.2 Reply-to Address Object ................................... 12
5.3 Previous Hop Address Object ............................... 13
6 Security Considerations ................................... 13
7 IANA Considerations ....................................... 13
7.1 Message and Object Type Assignments ....................... 14
7.2 Return Code Assignments ................................... 14
8 Acknowledgments ........................................... 14
9 References ................................................ 14
9.1 Normative References ...................................... 14
9.2 Informative References .................................... 15
10 Authors' Addresses ........................................ 15
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1. Introduction
It is anticipated that very large Point-to-Multipoint (P2MP) Label
Switched Paths (LSPs) will exist. Further it is anticipated that
many of the applications for P2MP tunnels will require OAM that is
both rigorous and scalable.
Suppose one wishes to trace a P2MP LSP to localize a fault which is
affecting one egress or a set of egresses. Suppose one follows the
normal procedure for tracing - namely repeatedly pinging from the
root, incrementing the TTL by one after each three or so pings. Such
a procedure has the potential for producing a large amount of pro-
cessing at the P2MP-LSP midpoints and egresses. It also could pro-
duce an unwieldy number of replies back to the root.
One alternative would be to begin sending pings from points at or
near the affected egress(es) and working backwards toward the root.
The TTL could be held constant as say two, limiting the the number of
responses to the number of next-next-hops of the point where the ping
was initiated.
The above procedure does require that the root know the previous-hop
node to the one which was pinged on the prior iteration. This infor-
mation is readily available in [P2MP-TE]. This document provides a
means for obtaining this information for [mLDP] as well as defining a
means for remotely causing an MPLS echo request message to be sent
down a Label Switched Path (LSP) or part of an LSP.
While the motivaton for this document came from multicast scaling
concerns, its applicability may be wider. However other uses of this
facility are beyond the scope of this document. Further the discus-
sion is cauched in terms of multipoint LSPs.
1.1. Conventions
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 [KeyWords].
The term "Must Be Zero" (MBZ) is used in object descriptions for
reserved fields. These fields MUST be set to zero when sent and
ignored on receipt.
Based on context the terms leaf and egress are used interchangeably.
Egress is used where consistency with [RFC4379] was deemed appropri-
ate. Receiver is used in the context of receiving protocol messages.
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[Note (to be removed after assignments occur): <tba> = to be assigned
by IANA]
2. Proxy Ping Overview
Two new LSP Ping messages are defined for remote pinging, the MPLS
proxy ping request and the MPLS proxy ping reply.
A remote ping operation on a P2MP LSP involves at least three LSRs;
in some scenarios none of these are the ingress (root) or an egress
(leaf) of the LSP.
We refer to these nodes with the following terms:
Initiator - the node which initiates the ping operation by sending
an MPLS proxy ping request message
Proxy LSR - the node which is the destination of the MPLS proxy
request message and potential initiator of the MPLS
echo request
Receiver(s) - the receivers of the MPLS echo request messages
The initiator formats an MPLS proxy ping request message and sends it
to the proxy LSR, a node it believes to be on the path of the LSP.
This message specifies the MPLS echo request to be sent inband of the
LSP. It may also request the proxy LSR to acknowledge the receipt of
the proxy ping request message and/or respond with the address of the
previous hop, i.e. the LSR upstream of it on this LSP.
The proxy LSR validates that it has a label mapping for the specified
FEC and that it is authorized to send the specified MPLS echo request
on behalf of the initiator. Depending on the Reply Mode carried in
the header of the proxy ping request message and the above results an
MPLS remote echo reply message might be sent back to the initiator.
This message may also communicate the address of the previous hop.
If the proxy LSR has a label mapping for the FEC and and all autho-
rization check have passed, the proxy LSR formats an MPLS echo
request. If the source address of the IP packet is not the initia-
tor, it includes a Reply-to Address object containing the initiator's
address. It then sends it inband of the LSP.
The receivers process the MPLS echo request as normal, sending their
MPLS echo replies back to the initiator.
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3. Remote Echo / Reply Pprocedures
3.1. Procedures for the initiator
The initiator creates an MPLS proxy ping request message.
The message MUST contain a Target FEC Stack that describes the FEC
being tested.
[Note for the current version of the ID, the FEC stack is limited to
a single FEC as we have not yet fully considered the operational and
security impacts of permitting more FECs]
The message MUST contain a Proxy Echo Parameters object. The address
type is set to either IPv4 or IPv6. The Destination IP Address is
set to the value to be used in the MPLS echo request packet. If the
Address Type is IPv4, an address from the range 127/8. If the
Address Type is IPv6, an address from the range
0:0:0:0:0:FFFF:127/104. By default the source address will be set to
an address of the proxy LSR.
The Reply mode and Global Flags of the Proxy Echo Parameters object
are set to the values to be used in the MPLS echo request message
header. The Source UDP Port is set to the value to be used in the
MPLS echo request packet. The TTL is set to the value to be used in
the outgoing MPLS label stack. See section 5.2.2.2 for further
details.
Flags MAY be set to request the previous hop address and/or a down-
stream mapping object from the proxy LSR.
A list of Next Hop IP Addresses MAY be included to limit the next
hops towards which the MPLS echo request message will be sent.
Any of following objects MAY be included; these objects will be
copied into the MPLS echo request messages:
Pad
Vendor Enterprise Number
Reply TOS Byte
P2MP Egress Identifier [McstPing]
Echo Jitter TLV [McstPing]
Vendor Private TLVs
Downstream Mapping objects MAY be included. These objects will be
matched to the next hop address for inclusion in those particular
MPLS echo request messages.
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The message is then encapsulated in a UDP packet. The source UDP
port is chosen by the sender; the destination UDP port is set to
3503. The IP header is set as follows: the source IP address is a
routable address of the sender; the destination IP address is a
routable address of the midpoint. The packet is then sent with the
IP TTL is set to 255.
3.2. Procedures for the proxy LSR
A proxy LSR that receives an MPLS proxy ping request message, parses
the packet to ensure that it is a well-formed packet. It checks that
the TLVs that are not marked "Ignore" are understood. If not, it
sets the Return Code set to "Malformed echo request received" or "TLV
not understood" (as appropriate), and the Subcode set to zero. If
the Reply Mode of the message header is not 0, an MPLS proxy ping
reply message SHOULD be sent as described below. In the latter case,
the misunderstood TLVs (only) are included in an Errored TLVs object.
The header fields Sender's Handle and Sequence Number are not exam-
ined, but are saved to be included in the MPLS proxy ping reply and
MPLS echo request messages.
The proxy LSR validates that it has a label mapping for the specified
FEC, it then determines if it is an egress, transit or bud node and
sets the Return Code as appropriate.
The proxy LSR then determines if it is authorized to send the speci-
fied MPLS echo request on behalf of the initiator. An LSR MUST be
capable of filtering addresses to validate initiators. Other filters
on FECs or MPLS echo request contents MAY be applied. If a filter
has been invoked (i.e. configured) and an address does not pass the
filter, then an MPLS echo request message MUST NOT be sent, and the
event SHOULD be logged. An MPLS proxy ping reply message may be sent
with a Return Code of <tba>, "Remote Ping not authorized".
If the "Request for Previous Hop" flag is set, a Previous Hop Address
Object is formatted for inclusion in the MPLS proxy ping reply. If
the previous HOP is unknown or ambiguous the Address Type is set to
"No Address Supplied".
If there is a list of Next Hop addresses in the Proxy Echo Parameters
object, each address is examined to determine if it is a next hop for
this FEC. If any are not, those addresses are deleted from the list.
The updated Proxy Echo Parameters object is included in the MPLS
proxy ping reply.
If the "Request for Downstream Mapping" flag is set the LSR formats a
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Downstream Mapping object for each interface that the MPLS echo
request will be sent out.
If the Reply Mode of the message header is not 0 or 5, an MPLS remote
echo reply message SHOULD be sent as described below.
3.2.1. Sending an MPLS proxy ping reply
The Reply mode, Sender's Handle and Sequence Number fields are copied
from the proxy ping request message. Various objects are included as
specified above. The message is encapsulated in a UDP packet. The
source IP address is a routable address of the proxy LSR; the source
port is the well-known UDP port for LSP ping. The destination IP
address and UDP port are copied from the source IP address and UDP
port of the echo request. The IP TTL is set to 255.
3.2.2. Sending the MPLS echo requests
A base MPLS echo request is formed as decribed in the next section.
The section below that describes how the base MPLS echo request is
sent on each interface.
3.2.2.1. Forming the base MPLS echo request
A Next_Hop_List is created as follows. If Next Hop addresses were
included in the received Proxy Parameters object, the Next_Hop_List
is copied from the Proxy Echo Parameters object as adjusted above.
Otherwise, the list is set to all the next hops to which the FEC
would be forwarded.
The proxy LSR then formats an MPLS echo request message. The Global
Flags and Reply Mode are copied from the Proxy Echo Parameters
object. The Return Code and Return Subcode are set to zero.
The Sender's Handle and Sequence Number are copied from the remote
echo request message.
The TimeStamp Sent is set to the time-of-day (in seconds and
microseconds) that the echo request is sent. The TimeStamp Received
is set to zero.
A Reply-to Address object containing the initiator's address is
included.
The following objects are copied from the MPLS proxy ping request
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Internet Draft draft-ietf-mpls-remote-lsp-ping-01.txt November 2007
message. Note that of these, only the Target FEC Stack is REQUIRED
to appear in the MPLS proxy ping request message.
Target FEC Stack
Pad
Vendor Enterprise Number
Reply TOS Byte
P2MP Egress Identifier [McstPing]
Echo Jitter TLV [McstPing]
Vendor Private TLVs
The message is then encapsulated in a UDP packet. The source UDP
port is copied from the Proxy Echo Parameters object. destination
ports are copied from the proxy ping request message.
The source IP address is set to a routable address of the proxy LSR.
Per usual the TTL of the IP packet is set to 1.
3.2.2.2. Per interface sending procedures
The proxy LSR now iterates through the Next_Hop_List modifying the
base MPLS echo request to form the MPLS echo request packet which is
then sent on that particular interface.
For each next hop address, the outgoing label stack is determained.
The TTL for the label corresponding to the FEC in the FEC stack is
set such that the TTL on the wire will be one less than the TTL spec-
ified in the proxy ping request message. If any additional labels
are pushed onto the stack, their TTLs are set to 255.
If the MPLS proxy ping request message contained Downstream Mapping
objects, they are examined. If the Downstream IP Address matches the
next hop address that Downstream Mapping object is included in the
MPLS echo request.
The packet is then transmitted on this interface.
4. Proxy Ping Request / Reply Messages
Two new LSP Ping messages are defined for remote pinging, the MPLS
proxy ping request message and the MPLS proxy ping reply.
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4.1. Proxy Ping Request / Reply Message formats
Except where noted, the definitions of all fields in the messages are
identical to those found in [LSP-PING]. The messages have the fol-
lowing format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Number | MUST Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Reply mode | Return Code | Return Subcode|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs ... |
. .
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version Number
The Version Number is currently 1. (Note: the Version Number is
to be incremented whenever a change is made that affects the
ability of an implementation to correctly parse or process an
MPLS echo request/reply. These changes include any syntactic or
semantic changes made to any of the fixed fields, or to any TLV
or sub-TLV assignment or format that is defined at a certain
version number. The Version Number may not need to be changed
if an optional TLV or sub-TLV is added.)
Message Type
Type Message
---- -------
5 MPLS proxy ping request
6 MPLS proxy ping reply
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Reply mode
The reply modes are the same as [LSP-PING] with the addtion of
value 5. For completeness, the full list of reply modes
follows:
Value Meaning
----- -------
1 Do not reply
2 Reply via an IPv4/IPv6 UDP packet
3 Reply via an IPv4/IPv6 UDP packet with Router Alert
4 Reply via application level control channel
5 Reply via an IPv4/IPv6 UDP packet only if the proxy
request is not fulfilled
4.2. Proxy Ping Request Message contents
The MPLS proxy ping request message MAY contain the following
objects:
Type Object
---- -----------
1 Target FEC Stack
2 Downstream Mapping
3 Pad
5 Vendor Enterprise Number
10 Reply TOS Byte
tba Proxy Echo Parameters
tba P2MP Egress Identifier [McstPing]
tba Echo Jitter TLV [McstPing]
Vendor Private TLVs
4.3. Proxy Ping Reply Message Contents
The MPLS proxy ping reply message MAY contain the following objects:
Type Object
---- -----------
1 Target FEC Stack
2 Downstream Mapping
5 Vendor Enterprise Number
9 Errored TLVs
tba Proxy Echo Parameters
tba Previous Hop Address
Vendor Private objects
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5. Object formats
5.1. Proxy Echo Parameters Object
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 | Flags | Reply mode | TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source UDP Port | Global Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Destination IP Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: :
: Next Hop IP Addresses :
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
The type of address found in the in the Destination IP Address
and Next Hop IP Addresses fields. The type codes appear in the
table below:
Address Family Type
IPv4 Numbered 1
IPv6 Numbered 3
Flags
Request for Previous Hop 0x01
When set this requests that the proxy LSR supply the previous hop
address in the MPLS proxy ping reply message
Request for Downstream Mapping 0x02
When set this requests that the proxy LSR supply a
Downstream Mapping object in the MPLS proxy ping reply
message
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Reply mode
The reply mode to be sent in the MPLS Echo Request message; the
values are as specified in [RFC4379]
TTL
The TTL to be used in the label corresponding to the FEC in the
MPLS Echo Request packet
Source UDP Port
The source UDP port to be sent in the MPLS Echo Request packet
Global Flags
The Global Flags to be sent in the MPLS Echo Request messge
Destination IP Address
If the Address Type is IPv4, an address from the range 127/8;
If the Address Type is IPv6, an address from the range
0:0:0:0:0:FFFF:127/104
Next Hop IP Addresses
A list of next hop address that the echo request message is to
be sent towards
5.2. Reply-to Address Object
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Reply-to Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Address Type
A type code as specified in the table below:
Type Type of Address
1 IPv4
3 IPv6
5.3. Previous Hop Address Object
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Type | MUST be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: Previous Hop Address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Address Type
A type code as specified in the table below:
Type Type of Address
0 No Address Supplied
1 IPv4
3 IPv6
6. Security Considerations
[To be written]
7. IANA Considerations
[Not complete]
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Internet Draft draft-ietf-mpls-remote-lsp-ping-01.txt November 2007
7.1. Message and Object Type Assignments
This document makes the following codepoint assigments (pending IANA
action):
Registry Codepoint Purpose
LSP Ping Message Type tba MPLS proxy ping request message
tba MPLS proxy ping reply
LSP Ping Object Type tba Proxy Echo Parameters
tba Reply-to Address
tba Previous Hop Address
7.2. Return Code Assignments
Value Meaning
tba Remote Ping not authorized
8. Acknowledgments
9. References
9.1. Normative References
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[KeyWords] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[McstPing] Farrel, A. et al, "Detecting Data Plane Failures in
Point-to-Multipoint MPLS Traffic Engineering -
Extensions to LSP Ping",
draft-ietf-mpls-p2mp-lsp-ping-02.txt, September 2006.
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Internet Draft draft-ietf-mpls-remote-lsp-ping-01.txt November 2007
9.2. Informative References
[P2MP-TE] Aggarwal, R., et al., "Extensions to RSVP-TE for
Point-to-Multipoint TE LSPs",
draft-ietf-mpls-rsvp-te-p2mp-07.txt, January 2007.
[mLDP] Minei, I., et. al., "Label Distribution Protocol
Extensions for Point-to-Multipoint and
Multipoint-to-Multipoint Label Switched Paths"
draft-ietf-mpls-ldp-p2mp-02.txt, October 2006.
10. Authors' Addresses
George Swallow
Cisco Systems, Inc.
1414 Massachusetts Ave
Boxborough, MA 01719
Email: swallow@cisco.com
Vanson Lim
Cisco Systems, Inc.
1414 Massachusetts Ave
Boxborough, MA 01719
Email: vlim@cisco.com
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