Internet A. Atlas, Ed.
Internet-Draft Google, Inc.
Expires: January 7, 2008 R. Bonica
Juniper Networks
JR. Rivers
Nuova Systems
N. Shen
E. Chen
Cisco Systems
July 6, 2007
Extending ICMP to Identify the Receiving Interface
draft-atlas-icmp-unnumbered-03
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
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.
This Internet-Draft will expire on January 7, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This memo defines ICMP extensions through which an router or host can
explicitly identify the interface upon which an undeliverable
Atlas, et al. Expires January 7, 2008 [Page 1]
Internet-Draft ICMP Unnumbered July 2007
datagram arrived. The incoming interface can be identified by
ifIndex, name, and/or address. The extensions defined herein are
particularly useful when troubleshooting networks with unnumbered
interfaces, parallel interfaces and/or asymmetric routing.
Table of Contents
1. Conventions Used In This Document . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Application to TRACEROUTE . . . . . . . . . . . . . . . . . . 4
4. Interface Information Object . . . . . . . . . . . . . . . . . 4
4.1. C-type meaning in an Interface Information Object . . . . 4
4.2. Interface Name Sub-Object . . . . . . . . . . . . . . . . 5
4.3. Interface Information Object Description . . . . . . . . . 6
4.4. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
Atlas, et al. Expires January 7, 2008 [Page 2]
Internet-Draft ICMP Unnumbered July 2007
1. 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 RFC2119 [RFC2119].
2. Introduction
IP devices use the Internet Control Message Protocol (ICMP) [RFC0792]
(ICMPv6) [RFC4443] to convey control information. In particular,
when an IP device receives a datagram that it cannot forward, it
sends an ICMP message to the datagram's originator. Network
operators and higher level protocols use these ICMP messages to
detect and diagnose network issues.
In the nominal case, the source address of the ICMP message
identifies the interface upon which the non-forwardable datagram
arrived. However, in many cases, the incoming interface is not
identified by the ICMP message at all. Details follow:
According to RFC1812 [RFC1812], when a router generates an ICMP
message, the source address of that ICMP message MUST be one of the
following:
o one of the IP addresses associated with the physical interface
over which the ICMP message is transmitted
o if that interface has no IP addresses associated with it, the
device's router-id or host-id is used instead.
If the following conditions are true, the source address of the ICMP
message identifies the interface upon which the non-forwardable
datagram arrived:
o the device originates an ICMP message through the same interface
upon which the non-forwardable datagram was received.
o that interface is numbered.
However, the transmitting and incoming interfaces may be different
due to an asymmetric return path, which can occur due to asymmetric
link costs, parallel links or ECMP. When a network uses unnumbered
interfaces, it is also not possible to identify the incoming
interface. The extensions defined in this memo permits an ICMP
originator to identify the interface through which the datagram that
elicited the ICMP messages arrived.
Using the extension defined herein, IP device can explicitly identify
the incoming interface by any or all of the following:
Atlas, et al. Expires January 7, 2008 [Page 3]
Internet-Draft ICMP Unnumbered July 2007
o IPv4 address
o IPv6 address
o name
o ifIndex
3. Application to TRACEROUTE
ICMP extensions defined in this memo support enhancements to
TRACEROUTE (the reasons are discussed in [RFC4884]). The enhanced
TRACEROUTE application, like older implementations, indicates which
nodes the original datagram visited en route to its destination. It
differs from older implementations in that it also reflects the
incoming interface on which the original triggering packet arrived,
even when that interface is unnumbered.
4. Interface Information Object
This section defines an ICMP extension object that can be appended to
the ICMPv4 Time Exceeded, ICMPv4 Destination Unreachable, ICMPv4
Parameter Problem, ICMPv6 Time Exceeded, and ICMPv6 Destination
Unreachable messages, as described in [RFC4884]. For the description
of the Interface Information Object, the incoming interface is the
one upon which the packet which triggered the ICMP message was
received. To minimize the use of extra bytes required for this
extension, there are four different pieces of information that can
appear in an Interface Information Object.
1. If the interface of interest has at least one IPv4 address and
the triggering packet was IPv4, then one of the interface's IPv4
addresses MAY be included.
2. If the interface of interest has at least one IPv6 address and
the triggering packet was IPv6, then one of the interface's IPv6
addresses MAY be included.
3. The ifIndex of the interface of interest MAY be included. This
is the ifIndex assigned to the interface by the router in as
specified by the Interfaces Group MIB [RFC2863].
4. An interface name string of no more than 31 bytes MAY be
included.
4.1. C-type meaning in an Interface Information Object
For this object, the c-type is split into two fields, a 2-bit
interface-role field and a 6-bit included-information field. This is
illustrated below.
Atlas, et al. Expires January 7, 2008 [Page 4]
Internet-Draft ICMP Unnumbered July 2007
Bit 7 6 | 5 4 3 2 1 0
+-------+-------+-------+-------+-------+-------+-------+-------+
| Interface Role| Rsvd | Rsvd | index | IPv4 | IPv6 | descr |
+-------+-------+-------+-------+-------+-------+-------+-------+
Interface Role: This 2-bit field [6:7] indicates the role of the
interface being identified. The enumerated values
are given below.
0 : This object describes the incoming interface.
1 : This object describes the outgoing interface.
2-3 : Undefined by this memo and to be assigned by IANA
Included Information: This 6-bit field [0:5] indicates what
information is included in the object. The
information must be included in the same order
as the bits (from highest to lowest).
bit
5 : This bit is reserved for future use and MUST be set to 0.
4 : This bit is reserved for future use and MUST be set to 0.
3 : When set, this bit indicates the ifIndex of the interface
is included. When clear, the ifIndex is not included.
2 : When set, this indicates an IPv4 address of the interface
is included. When clear, no IPv4 address is included.
1 : When set, this indicates an IPv6 address of the interface
is included. When clear, no IPv6 address is included.
0 : When set, this indicates an Interface Name Sub-object for
the interface is included. When clear, it is not included.
C-Type for the Interface Information Object
4.2. Interface Name Sub-Object
The Interface Name Sub-Object MUST have a length that is a multiple
of 4 bytes and MUST NOT exceed 32 bytes; the string should be padded
with zeroes as necessary. The interface name SHOULD be the MIB-II
ifName [RFC2863] but MAY be some other human-meaningful name of the
interface.
The Interface Name Sub-Object consists of two fields. The first
1-byte field indicates the character set type used by the second
field. The second field contains the human-readable name.
Atlas, et al. Expires January 7, 2008 [Page 5]
Internet-Draft ICMP Unnumbered July 2007
byte 0 1 31
+--------------+----..............-------+
| charset type | interface name |
+--------------+----..............-------+
Interface Name Sub-Object
charset type 0 : This indicates that the human-readable interface
name MUST be provided in the US-ASCII charset [US-ASCII] using the
Default Language [RFC2277].
charset type 1 : This indicates that the human-readable interface
name MUST be provided in the UTF-8 charset [RFC3629] using the
Default Language [RFC2277].
4.3. Interface Information Object Description
Figure 3 depicts the Interface Information Object, with some valid
permutations. It must be preceded by an ICMP Extension Structure
Header and an ICMP Object Header. Both are defined in [RFC4884].
Although all examples show an Interface Name Sub-object of length 32,
this is only for illustration and depicts the maximum allowable
length.
Class-Num = 2
Example 1: Interface with only interface name
C-Type = 00000001b // Indicates incoming interface
Length = 36 (4 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name, word 8 |
+--------------+--------------+--------------+--------------+
Example 2: Interface with only ifIndex
C-Type = 00001000b // Indicates incoming interface
Length = 8 (4 + 4)
0 1 2 3
Atlas, et al. Expires January 7, 2008 [Page 6]
Internet-Draft ICMP Unnumbered July 2007
+--------------+--------------+--------------+--------------+
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
Example 3: Unnumbered Interface with ifIndex and interface name
C-Type = 00001001b // Indicates incoming interface
Length = 40 (4 + 4 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name , word 8 |
+--------------+--------------+--------------+--------------+
Example 4: IPv4 interface with ifIndex and interface name
C-Type = 00001101b // Indicates incoming interface
Length = 44 (4 + 4 + 4 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
| IPv4 address |
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name, word 8 |
+--------------+--------------+--------------+--------------+
Example 5: IPv4 interface with ifIndex
C-Type = 00001100b // Indicates incoming interface
Length = 12 (4 + 4 + 4)
0 1 2 3
+--------------+--------------+--------------+--------------+
Atlas, et al. Expires January 7, 2008 [Page 7]
Internet-Draft ICMP Unnumbered July 2007
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
| IPv4 address |
+--------------+--------------+--------------+--------------+
Example 6: IPv4 interface with interface name
C-Type = 00000101b // Indicates incoming interface
Length = 40 (4 + 4 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| IPv4 address |
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name , word 8 |
+--------------+--------------+--------------+--------------+
Example 7: IPv6 interface with ifIndex and interface name
C-Type = 00001011b // Indicates incoming interface
Length = 56 (4 + 4 + 16 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 1 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 2 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 3 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 4 |
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name, word 8 |
+--------------+--------------+--------------+--------------+
Atlas, et al. Expires January 7, 2008 [Page 8]
Internet-Draft ICMP Unnumbered July 2007
Example 8: IPv6 interface with ifIndex
C-Type = 00001010b // Indicates incoming interface
Length = 24 (4 + 4 + 16)
0 1 2 3
+--------------+--------------+--------------+--------------+
| Interface ifIndex |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 1 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 2 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 3 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 4 |
+--------------+--------------+--------------+--------------+
Example 9: IPv6 interface with interface name
C-Type = 00000011b // Indicates incoming interface
Length = 52 (4 + 16 + 32)
0 1 2 3
+--------------+--------------+--------------+--------------+
| IPv6 address, word 1 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 2 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 3 |
+--------------+--------------+--------------+--------------+
| IPv6 address, word 4 |
+--------------+--------------+--------------+--------------+
| Interface Name, word 1 |
+--------------+--------------+--------------+--------------+
... ...
+--------------+--------------+--------------+--------------+
| Interface Name , word 8 |
+--------------+--------------+--------------+--------------+
Figure 3: Interface Information Object
Atlas, et al. Expires January 7, 2008 [Page 9]
Internet-Draft ICMP Unnumbered July 2007
4.4. Usage
If the incoming interface is unnumbered for the triggering packet
type, then an Interface Information Object of c-type 8 or 9 SHOULD be
included in the ICMPv4 or ICMPv6 Time Exceeded or ICMPv4 or ICMPv6
Destination Unreachable message.
If the triggering packet is IPv4 and the incoming interface has an
IPv4 address, then an Interface Information Object of c-type 4, 5,
12, or 13 MAY be included in the ICMPv4 Time Exceeded and ICMPv4
Destination Unreachable messages.
If the triggering packet is IPv6 incoming interface has an IPv6
address, then an Interface Information Object of c-type 2, 3, 10, or
11 MAY be included in the ICMPv6 Time Exceeded and ICMPv6 Destination
Unreachable messages.
In an ICMP message, more than one Interface Information Object with a
given interface role MUST NOT be included. Multiple Interface
Information Objects, each with a different interface role, MAY be
included.
5. Security Considerations
This extension can provide the user of traceroute with additional
network information that is not currently available. It may be
desirable to provide this information to a particular network's
operators and not to others. If such policy controls are desirable,
then an implementation could determine what sub-objects to include
based upon the destination IP address of the ICMP message. For
instance, the ifIndex might be appropriate for all potential
recipients; the interface name could be included as well if the
destination IP address is a management address of the network that
has administrative control of the router.
6. IANA Considerations
IANA should should reserve from the ICMP Extension Object registry: 2
for the Interface Information Object. IANA should reserve from the
Interface ID Object's c-type, bit 0 for the inclusion of the
interface name sub-object, bit 1 for inclusion of an IPv6 address,
bit 2 for inclusion of an IPv4 address, and bit 3 for inclusion of an
ifIndex. Bits 4 and 5 are unallocated and IANA should create a
registry to allocate those with a requirement for standards action.
Bit 6 and 7 form the Interface Role field. Value 0 should be
allocated for incoming interface; value 1 should be allocated for
Atlas, et al. Expires January 7, 2008 [Page 10]
Internet-Draft ICMP Unnumbered July 2007
outgoing interface. Values 2 and 3 are unallocated and IANA should
allocate those with a requirement for standards action.
Additionally, the Interface Name Sub-Object has a 1 byte charset type
field. IANA should create a registry from it and allocate 0 for
names in ASCII and 1 for names in UTF-8. The remaining values should
be allocated on a first come basis.
7. Acknowledgements
The authors would like to thank Carlos Pignataro, Sasha Vainshtein,
and Joe Touch for their comments and suggestions.
8. References
8.1. Normative References
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884,
April 2007.
8.2. Informative References
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers",
RFC 1812, June 1995.
[RFC2277] Alvestrand, H., "IETF Policy on Character Sets and
Languages", BCP 18, RFC 2277, January 1998.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
Atlas, et al. Expires January 7, 2008 [Page 11]
Internet-Draft ICMP Unnumbered July 2007
[US-ASCII]
"Coded Character Set -- 7-bit American Standard Code for
Information Interchange, ANSI X3.4-1986".
Authors' Addresses
Alia K. Atlas (editor)
Google, Inc.
One Broadway, 7th Floor
Cambridge, MA 02142
USA
Email: akatlas@google.com
Ronald P. Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
USA
Email: rbonica@juniper.net
J.R. Rivers
Nuova Systems
Email: jrrivers@nuovasystems.com
Naiming Shen
Cisco Systems
225 West Tasman Drive
San Jose, CA 95134
USA
Email: naiming@cisco.com
Enke Chen
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: enkechen@cisco.com
Atlas, et al. Expires January 7, 2008 [Page 12]
Internet-Draft ICMP Unnumbered July 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
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.
Intellectual Property
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.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Atlas, et al. Expires January 7, 2008 [Page 13]
