The MPLS WG Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] MPLS+ICMP
Shahram,
A copy of the draft is attached.
Note that that there is a small problem on the figure in Section 6.4. The
text in the figure does not match the text in the section. The text in the
figure should read "Additional Bytes of Message Body".
George, Vijay,
Is there anything that I need to do to progress this draft or at least
unexpire it. It has already passed WG last call.
Ron
> -----Original Message-----
> From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of Shahram
> Davari
> Sent: Tuesday, July 25, 2000 9:43 AM
> To: 'mpls@UU.net'
> Subject: MPLS+ICMP
>
>
> Hi,
>
> Does anybody have the following draft, which is expired:
>
> draft-ietf-mpls-icmp-02.txt
>
> Thanks,
>
> Shahram Davari
> Systems Engineer
> Product Research
> PMC-Sierra, Inc. (Ottawa)
> 555 Legget drive,
> Suit 834, Tower B,
> Ottawa, ON K2K 2X3, Canada
> Phone: +1 (613) 271-4018
> Fax : +1 (613) 271-7007
>
>
>
>
MPLS Working Group R.Bonica
Internet Draft MCIWorldCom
Document: draft-ietf-mpls-icmp-01.txt D.Tappan
Cisco Systems
D.Gan
Juniper Networks
December 1999
ICMP Extensions for MultiProtocol Label Switching
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC-2026].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
1. Abstract
The current memo proposes extensions to ICMP that permit Label
Switching Routers to append MPLS information to ICMP messages.
2. 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].
3. Introduction
Routers and destination hosts use the Internet Control Message
Protocol (ICMP) [RFC-792] to convey control information to source
hosts. Network operators use this information to diagnose routing
problems.
Bonica, Tappan, Hwa Draft-Expires May 2000 1
ICMP Extensions for MPLS December 1999
When a router receives an undeliverable IP datagram, it can send an
ICMP message to the host that originated the datagram. The ICMP
message indicates why the datagram could not be delivered. It also
contains the IP header and leading payload octets of the "original
datagram".
In this document, the term "original datagram" refers to the
datagram to which the ICMP message is a response.
MPLS Label Switching Routers (LSR) also use ICMP to convey control
information to source hosts. Sections 2.3 and 2.4 of [ENCODE]
describe the interaction between MPLS and ICMP.
When an LSR receives an undeliverable MPLS encapsulated datagram, it
removes the entire MPLS label stack, exposing the previously
encapsulated IP datagram. The LSR then submits the IP datagram to a
network-forwarding module for error processing. Error processing can
include ICMP message generation.
The ICMP message indicates why the original datagram could not be
delivered. It also contains the IP header and leading octets of the
original datagram.
The ICMP message, however, includes no information regarding the
MPLS label stack that encapsulated the original datagram when it
arrived at the LSR. This omission is significant because the LSR
would have routed the original datagram based upon information
contained by the MPLS label stack.
The current memo proposes extensions to ICMP that permit an LSR to
append MPLS label stack information to ICMP messages. ICMP messages
regarding MPLS encapsulated datagrams SHOULD include the MPLS label
stack, as it arrived at the router that is sending the ICMP message.
The ICMP message MUST also include the IP header and leading payload
octets of the original datagram.
Network operators will use this information to diagnose routing
problems.
4. Motivation
ICMP extensions defined in the current memo support enhancements to
TRACEROUTE. The enhanced TRACEROUTE, like older implementations,
indicates which nodes the original datagram visited en route to its
ultimate destination. It differs from older implementations in that
it also indicates the original datagrams MPLS encapsulation status
as it arrived at each node.
Figure 1 contains sample output from an enhanced TRACEROUTE
implementation.
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ICMP Extensions for MPLS December 1999
>Traceroute 166.45.2.74
traceroute to 166.45.2.74, 30 hops max, 40 byte packets
1 166.45.5.1 1.281 ms 1.103 ms 1.096 ms
2 166.45.4.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2001
mplsExpBits1=0
3 166.45.3.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2002
mplsExpBits1=0
4 166.45.6.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2003
mplsExpBits1=0
5 166.45.2.1 1.281 ms 1.103 ms 1.096 ms
6 166.45.2.74 1.281 ms 1.103 ms 1.096 ms
Figure 1. Enhanced TRACEROUTE sample output
5. Disclaimer
The current memo does not define the general relationship between
ICMP and MPLS. Sections 2.3 and 2.4 of [ENCODE] define this
relationship.
Specifically, this document defers to [ENCODE] with respect to the
following issues:
-
conditions upon which an LSR emits ICMP messages
-
handling of ICMP messages bound for hosts that are identified
by private addresses
The current memo does not define encapsulation specific TTL
manipulation procedures. It defers to Section 10 of [MPLSATM] and
Section 5.4 of [MPLSFRAME] in this matter.
When encapsulation specific TTL manipulation procedures defeat the
basic TRACEROUTE mechanism, they will also defeat enhanced
TRACEROUTE implementations.
The current memo does not address extensions to ICMPv6. These should
be addressed in a separate draft.
6. Formal Syntax
This section defines a data structure that an LSR can append to
selected ICMP messages. The data structure contains the MPLS label
stack that encapsulated the original datagram when it arrived at the
LSR.
The data structure defined herein can be appended to the following
ICMP message types:
Bonica,Tappan,Gan Draft-Expires May 2000 3
ICMP Extensions for MPLS December 1999
1) Destination Unreachable
2) Time Exceeded
3) Parameter Problem
4) Source Quench
5) Redirect
According to RFC-792, the final field contained by each of these
ICMP message types reflects the IP header and leading 64 bits of the
original datagram. [RFC-1812] recommends that this final field be
extended to include as much of the original datagram as possible.
When an LSR appends the data structure defined herein to an ICMP
message, the final field of the ICMP message body MUST contain the
first 128 octets of the original datagram. At least 20 of these 128
octets represent the IP header of the original datagram.
If the original datagram was shorter than 128 octets, the final
field MUST be padded with 0's.
When an LSR appends the data structure defined herein to an ICMP
message, the ICMP "total length" MUST be equal to the data structure
length plus 156. The first octet of the data structure must be
displaced 156 octets from the beginning of the ICMP message.
The data structure defined in this section consists of a common
header followed by object instances. Each object instance consists
of an object header plus contents.
Currently, two object classes are defined. One object class contains
an entire MPLS label stack, formatted exactly as it was when it
arrived at the LSR that sends the ICMP message. The other contains
some portion of the original datagram that could not be included in
the final field of the ICMP message body (i.e., the octet 129 and
beyond).
Both object classes are optional.
In the future, additional object classes may be defined.
6.1 Common Header
0 1 2 3
+-------------+-------------+-------------+-------------+
| Vers | (Reserved) | Checksum |
+-------------+-------------+-------------+-------------+
The fields in the common header are as follows:
Bonica,Tappan,Gan Draft-Expires May 2000 4
ICMP Extensions for MPLS December 1999
Vers: 4 bits
ICMP extension version number.
This is version 2.
Checksum: 16 bits
The one's complement of the one's complement sum of the data
structure, with the checksum field replaced by zero for the purpose
of computing the checksum. An all-zero value means that no checksum
was transmitted.
If the checksum field contains a value other than described above,
the ICMP message does not include the extensions described in this
memo. This, however, does not imply that the ICMP message is
malformed. It may be in strict compliance with RFC-1812.
Reserved: Must be set to 0.
6.2 Object Header
Every object consists of one or more 32-bit words with a one-word
header, with the following format:
+-------------+-------------+-------------+-------------+
| Length | Class-Num | C-Type |
+-------------+-------------+-------------+-------------+
| |
| // (Object contents) // |
| |
+-------------+-------------+-------------+-------------+
An object header has the following fields:
Length: 16 bits
Length of the object, measured in octets, including the object
header and object contents.
Class-Num: 8 bits
Identifies object class.
C-Type: 8 bits
Identifies object sub-type.
Bonica,Tappan,Gan Draft-Expires May 2000 5
ICMP Extensions for MPLS December 1999
6.3 MPLS Stack Entry Object Class
A single instance of the MPLS Entry Object class represents the
entire MPLS label stack, formatted exactly as it was when it arrived
at the LSR that sends the ICMP message
In the illustration below, octets 0-3 depict the first member of the
MPLS label stack. Each remaining member of the MPLS label stack is
represented by another 4 octets that share the same format.
Syntax follows:
MPLS Stack Entry Class = 1, C-Type = 1.
0 1 2 3
+-------------+-------------+-------------+-------------+
| Label |EXP |S| TTL |
+-------------+-------------+-------------+-------------+
| |
| // Remaining MPLS Stack Entries // |
| |
+-------------+-------------+-------------+-------------+
Label: 20 bits
Exp: Experimental Use, 3 bits
S: Bottom of Stack, 1 bit
TTL: Time to Live, 8 bits
6.4 Extended Payload Object Class
An instance of the Extended Payload Object class represents some
portion of the original datagram that could not be fit in the final
field of the ICMP message body (i.e., octets beyond 128).
Syntax follows:
MPLS Stack Entry Class = 2, C-Type = 1.
0 1 2 3
+-------------+-------------+-------------+-------------+
| |
| // Remaining MPLS Stack Entries // |
| |
+-------------+-------------+-------------+-------------+
Bonica,Tappan,Gan Draft-Expires May 2000 6
ICMP Extensions for MPLS December 1999
7. Backward Compatibility
ICMP extensions proposed in this document MUST be backward
compatible with the syntax described in RFC-792. Extensions proposed
in this memo MUST NOT change or deprecate any field defined in RFC-
792.
The extensions defined herein are in keeping with the spirit, if not
the letter of RFC-1812. In order to support IP-in-IP tunneling, RFC-
1812 extends the final field of selected ICMP messages to include a
greater portion of the original datagram. Unfortunately, it extends
this field to a variable length without adding a length attribute.
This memo binds the length of that final field to an arbitrarily
large value (128 octets). Fixing the length of that field
facilitates extension of the ICMP message. An additional object is
provided through which octets 129 and beyond can be appended to the
ICMP message.
As few datagrams contain L3 or L4 header information beyond octet
128, it is unlikely that the extensions described herein will
disable any applications that rely upon RFC-1812 style ICMP
messages.
8. Security Considerations
This memo presents no security considerations beyond those already
presented by current ICMP applications (e.g., traceroute).
9. References
[ARCH], Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", Internet Draft <draft-ietf-mpls-arch-
06.txt>, August, 1999
[ENCODE], Rosen, E., Rekhter, Y., Tappan, D, Farinacci, D.,
Fedorkow, G., Li, T., Conta, A., "MPLS Stack Encoding", Internet
Draft, <draft-ietf- -
mpls label-encapse-07.txt>, September 1999.
[FRAME], Callon, R., Doolan, P., Feldman, N., Fredette, A., Swallow,
G., and A. Viswanathan, "A Framework for Multiprotocol Label
Switching", Internet Draft <draft-ietf-mpls-framework-05.txt>,
September 1999.
[MPLSATM], Davie, B., Lawrence, J., McCloghrie, K., Rekhter, Y.,
Rosen, E., Swallow, G, "MPLS using ATM VC Switching", <draft-ietf-
mpls-atm-01.txt>, November, 1998.
Bonica,Tappan,Gan Draft-Expires May 2000 7
ICMP Extensions for MPLS December 1999
[MPLSFRAME], Conta, A., Doolan, P., Malis, A., "Use of Label
Switching on Frame Relay Networks", <draft-ietf-mpls-fr-03.txt>,
November, 1998.
[RFC-792], Postel, J., "Internet Control Message Protocol", RFC 792,
ISI, September 1981.
[RFC-1812], Baker, F., "Requirements for IP Version 4 Routers", RFC
1812, June 1995.
[RFC-2026], Bradner, S., "Internet Standards Process Revision 3",
RFC 2026, Harvard University, October 1996.
[RFC-2119], Bradner, S,, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997
10. Acknowledgments
Thanks to Yakov Rekhter and Mike Heard for their contributions to
this memo.
11. Author's Addresses
Ronald P. Bonica
MCI WorldCom
22001 Loudoun County Pkwy
Ashburn, Virginia, 20147
Phone: 703 886 1681
Email: rbonica@mci.net
Daniel C. Tappan
Cisco Systems
250 Apollo Drive
Chelmsford, Massachusetts, 01824
Email: tappan@cisco.com
Der-Hwa Gan
Juniper Networks
385 Ravendale Drive
Mountain View, California 94043
Email: dhg@juniper.net
Bonica,Tappan,Gan Draft-Expires May 2000 8
ICMP Extensions for MPLS December 1999
Full Copyright Statement
"Copyright (C) The Internet Society (date). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into
Bonica,Tappan,Gan Draft-Expires May 2000 9
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