Internet R. Bonica
Internet-Draft D. Gan
Expires: December 11, 2006 Juniper Networks
P. Nikander
Ericsson Research Nomadic Lab
D. Tappan
C. Pignataro
Cisco Systems, Inc.
June 9, 2006
Modifying ICMP to Support Multi-part Messages
draft-bonica-internet-icmp-06
Status of this Memo
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This Internet-Draft will expire on December 11, 2006.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document redefines selected ICMPv4 messages to support multi-
part operation. A multi-part ICMP message carries all of the
information that ICMP messages carried previously, as well as
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additional information that applications may require.
Multi-part messages are supported by an ICMP extension structure.
The extension structure is situated at the end of the ICMP message.
It includes an extension header followed by one or more extension
objects. Each extension object contains an object header and object
payload. All object headers share a common format.
This document further redefines a subset of the above mentioned ICMP
messages by specifying a length attribute. Many of the ICMP messages
to which an extension structure can be appended include and "original
datagram" field. The "original datagram" field contains the initial
octets of the datagram to which the ICMP message is a response.
Although the original datagram field is of variable length, the ICMP
message does not include a field that specifies its length.
Therefore, in order to facilitate message parsing, this draft
allocates eight previously reserved bits to reflect the length of the
"original datagram" field.
The proposed modifications change the requirements for ICMPv4
compliance. The impact of these changes on compliant implementations
is discussed, and new requirements for future implementations are
presented.
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Table of Contents
1. Conventions Used In This Document . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Summary of Changes to ICMP . . . . . . . . . . . . . . . . . . 5
4. ICMP Extensibility . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Destination Unreachable . . . . . . . . . . . . . . . . . 7
4.2. Source Quench . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Time Exceeded . . . . . . . . . . . . . . . . . . . . . . 9
4.4. Parameter Problem . . . . . . . . . . . . . . . . . . . . 9
4.5. ICMP Messages That Can Be Extended . . . . . . . . . . . . 10
5. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 10
5.1. Classic Application Receives ICMP Message With
Extensions . . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Non-compliant Application Receives ICMP Message With
No Extensions . . . . . . . . . . . . . . . . . . . . . . 12
5.3. Non-compliant Application Receives ICMP Message With
Compliant Extensions . . . . . . . . . . . . . . . . . . . 13
5.4. Compliant Application Receives ICMP Message with No
Extensions . . . . . . . . . . . . . . . . . . . . . . . . 13
5.5. Compliant Application Receives ICMP Message with
Non-compliant Extensions . . . . . . . . . . . . . . . . . 13
6. The ICMP Extension Structure . . . . . . . . . . . . . . . . . 14
7. ICMP Extension Objects . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 19
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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 [1].
2. Introduction
This document redefines selected ICMP [2] messages to include an
extension structure and a length attribute. In this document, the
term ICMP refers exclusively to ICMPv4. Unless explicitly noted,
ICMPv6 is NOT discussed in this memo.
The extension structure supports multi-part ICMP operation. Protocol
designers can make an ICMP message carry additional information by
encoding that information in an extension.
This document also addresses a fundamental problem in ICMP
extensibility. Many of the ICMP messages addressed by this memo
include an "original datagram" field. The "original datagram" field
contains the initial octets of the datagram to which the ICMP message
is a response. Although the "original datagram" field is of variable
length, the ICMP message does not include a field that specifies its
length.
Application software infers the length of the "original datagram"
field from the total length of the ICMP message. If an extension
structure were appended to the message without adding a length
attribute for the "original datagram" field, the message would become
unparsable. Specifically, application software would not be able to
determine where the "original datagram" field ends and where the
extension structure begins. Therefore, this document proposes a
length attribute as well as an extension structure that is appended
to the ICMP message.
The current memo also addresses backwards compatibility with existing
ICMP implementations that either do not implement the extensions
defined herein or implement them without adding the required length
attributes. In particular, this draft addresses backwards
compatibility with certain, widely deployed, MPLS-aware ICMP
implementations that send the extensions defined herein without
adding the required length attribute.
The current memo does not define any ICMP extension objects. It
defines only the extension header and a common header that all
extension objects share. Reference [5] provides a sample application
of the ICMP Extension Object.
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3. Summary of Changes to ICMP
The following is a summary of changes to ICMP that are proposed by
this memo:
An ICMP Extension Structure MAY be appended to ICMP Destination
Unreachable, Source Quench, Time Exceeded, and Parameter Problem
messages.
These messages include an "original datagram" field, and the
message formats are updated to specify a length attribute for the
"original datagram" field.
The "original datagram" field MUST include at least 128 octets.
If the original datagram did not contain 128 octets, the "original
datagram" field MUST be zero padded to 128 octets.
The "original datagram" field MUST be zero padded to the nearest
32-bit boundary.
4. ICMP Extensibility
RFC 792 defines the following ICMP message types:
- Destination Unreachable
- Time Exceeded
- Parameter Problem
- Source Quench
- Redirect
- Echo Request/Reply
- Timestamp/Timestamp Reply
- Information Request/Information Reply
RFC 1191 [3] adds a "Next-Hop MTU" field to the Destination
Unreachable message. Subsequent RFCs define the following messages:
- Address Mask Request/Reply [6]
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- Router Solicitation/Advertisement [7]
- Traceroute [8]
- Domain Name Request/Reply [9]
- Security Failure [10]
- Experimental Mobility [11]
Many ICMP messages are extensible as currently defined. Protocol
designers can extend ICMP messages by simply appending fields or data
structures to them.
The following ICMP messages are not extensible as currently defined:
- Destination Unreachable
- Source Quench
- Time Exceeded
- Parameter Problem
- Redirect
- Echo Request
- Echo Reply
- Domain Name Reply
These ICMP messages contain an "original datagram" field which
represents a portion of the original datagram to which the ICMP
messages is a response. As originally defined, this field includes
the IP header plus the next eight octets of the original datagram.
RFC 1812 [4] extends this field to contain as many octets as
possible, without exceeding a limit of 576 octets for the entire ICMP
message.
Unfortunately, the "original datagram" field lacks a length
attribute. Application software infers the length of this field from
the total length of the ICMP message. If an extension structure were
appended to the message without adding a length attribute for the
"original datagram" field, the message would become unparsable.
Specifically, application software would not be able to determine
where the "original datagram" field ends and where the extension
structure begins.
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In order to solve this problem, this memo introduces an 8-bit length
attribute to the following ICMP messages.
- Destination Unreachable
- Source Quench
- Time Exceeded
- Parameter Problem
The length attribute MUST be specified when the ICMP Extension
Structure is appended to the above mentioned ICMP messages.
The length attribute represents the length of the "original datagram"
field, measured in 32-bit words. When the length attribute is
specified, the "original datagram" field MUST be zero padded to the
nearest 32-bit boundary. Space for the length attribute is claimed
from reserved octets, whose value was previously required to be zero.
Because the sixth octet of each of the impacted ICMP messages was
reserved for future use, this octet was selected as the location of
the length attribute.
In order the achieve backwards compatibility, when the ICMP Extension
Structure is appended to an ICMP message and that ICMP message
contains an "original datagram" field, the "original datagram" field
MUST contain at least 128 octets. If the original datagram did not
contain 128 octets, the "original datagram" field MUST be zero padded
to 128 octets. (See Section 5.1 for rationale.)
The following sub-sections depict length attribute as it has been
introduced to selected ICMP messages.
4.1. Destination Unreachable
Figure 1 depicts the Destination Unreachable Message.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unused | Length | Next-Hop MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Header + leading octets of original datagram |
| |
| // |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Destination Unreachable
The syntax and semantics of all fields are unchanged from RFC 792 and
RFC 1191. However, a length attribute is added to the second word.
The length attribute represents length of the padded "original
datagram" field, measured in 32-bit words.
4.2. Source Quench
Figure 2 depicts the Source Quench Message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unused | Length | unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Header + leading octets of original datagram |
| |
| // |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Source Quench
The syntax and semantics of all fields are unchanged from RFC 792,
except for a length attribute which is added to the second word. The
length attribute represents length of the padded "original datagram"
field, measured in 32-bit words.
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4.3. Time Exceeded
Figure 3 depicts the Time Exceeded Message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| unused | Length | unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Header + leading octets of original datagram |
| |
| // |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Time Exceeded
The syntax and semantics of all fields are unchanged from RFC 792,
except for a length attribute which is added to the second word. The
length attribute represents length of the padded "original datagram"
field, measured in 32-bit words.
4.4. Parameter Problem
Figure 4 depicts the Parameter Problem Message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pointer | Length | unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Header + leading octets of original datagram |
| |
| // |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Parameter Problem
The syntax and semantics of all fields are unchanged from RFC 792,
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except for a length attribute which is added to the second word. The
length attribute represents length of the padded "original datagram"
field, measured in 32-bit words.
4.5. ICMP Messages That Can Be Extended
An ICMP Extension Structure MAY be appended to ICMP Destination
Unreachable, Source Quench, Time Exceeded, and Parameter Problem
messages. The ICMP Extension Structure cannot be appended to any of
the other ICMP messages mentioned in Section 4.
ICMP messages defined in the future should indicate whether or not
they support the extension mechanism defined in this specification.
It is recommended that all new messages employ some mechanism that
allows later extensions.
5. Backwards Compatibility
ICMP messages can be categorized as follows:
- Messages that do not include any ICMP extensions
- Messages that include non-compliant ICMP extensions
- Messages that includes compliant ICMP extensions
Any ICMP implementation can send a message that does not include
extensions. ICMP implementations produced prior to 1999 are not
known to send ICMP extensions.
Some ICMP implementations, produced between 1999 and the present, may
send a non-compliant version of ICMP extensions described in this
memo. Specifically, these implementations may append the ICMP
Extension Structure to the Time Exceeded and Destination Unreachable
messages. When they do this, they send exactly 128 octets
representing the original datagram, zero padding if required. They
also calculate checksums as described in this document. However,
they do not specify a length attribute to be associated with the
"original datagram" field.
It is assumed that ICMP implementations produced in the future will
send ICMP extensions that are compliant with this specification.
Likewise, applications that consume ICMP messages can be categorized
as follows:
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- Classic applications
- Non-compliant applications
- Compliant applications
Classic applications do not parse extensions defined in this memo.
They are insensitive to the length attribute that is associated with
the "original datagram" field.
Non-compliant implementations parse the extensions defined in this
memo, but only in conjunction with the Time Expired and Destination
Unreachable messages. They require the "original datagram" field to
contain exactly 128 octets and are insensitive to the length
attribute that is associated with the "original datagram" field.
Non-compliant applications were produced between 1999 and the
present.
Compliant applications comply fully with the specifications of this
document.
In order to demonstrate backwards compatibility, Table 1 describes
how members of each application category would parse each category of
ICMP message.
+----------------+----------------+----------------+----------------+
| | No Extensions | Non-compliant | Compliant |
| | | Extensions | Extensions |
+----------------+----------------+----------------+----------------+
| Classic | - | Section 5.1 | Section 5.1 |
| Application | | | |
| | | | |
| Non-compliant | Section 5.2 | - | Section 5.3 |
| Application | | | |
| | | | |
| Compliant | Section 5.4 | Section 5.5 | - |
| Application | | | |
+----------------+----------------+----------------+----------------+
Table 1
In the table above, cells that contain a dash represent the nominal
case and require no explanation. In the following sections, we
assume that the ICMP message type is "Time Exceeded".
5.1. Classic Application Receives ICMP Message With Extensions
When a classic application receives an ICMP message that includes
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extensions, it will incorrectly interpret those extensions as being
part of the "original datagram" field. Fortunately, the extensions
are guaranteed to begin at least 128 octets beyond the beginning of
the "original datagram" field. So, only those ICMP applications that
process the 129th octet of the "original datagram" field will be
adversely effected. To date, no such applications have been
identified.
5.2. Non-compliant Application Receives ICMP Message With No Extensions
When a non-compliant application receives a message that contains no
extensions, the application examines the total length of the ICMP
message. If the total ICMP message length is less than the length of
its IP header plus 144 octets, the application correctly determines
that the message does not contain any extensions.
The 144 octet sum is derived from 8 octets for the first two words of
the ICMP Time Exceeded message, 128 octets for the "original
datagram" field, 4 octets for the ICMP Extension Header and 4 octets
for a single ICMP Object header. All of these octets would be
required if extensions were present.
If the ICMP payload contains 144 octets or more, the application must
examine the 137th octet to determine whether it represents a valid
ICMP Extension Header. In order to represent a valid Extension
Header, it must contain a valid version number and checksum. If it
does not contain a valid version number and checksum, the application
correctly determines that the message does not contain any
extensions.
Non-compliant applications assume that the ICMP Extension Structure
begins on the 137th octet of the Time Exceeded message, after a 128
octet field representing the padded "original datagram" message.
It is possible that a non-compliant application will parse an ICMP
message incorrectly under the following conditions:
- the message does not contain extensions
- the original datagram field contains 144 octets or more
- selected octets of the original datagram field represent the
correct values for an extension header version number and checksum
Although this is possible, it is very unlikely.
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5.3. Non-compliant Application Receives ICMP Message With Compliant
Extensions
When a non-compliant application receives a message that contains
compliant ICMP extensions, it will parse those extensions correctly
only if the "original datagram" field contains exactly 128 octets.
This is because non-compliant applications are insensitive to the
length attribute that is associated with the "original datagram"
field. (They assume its value to be 128.)
Provided that the entire ICMP messages does not exceed 576 octets,
there is no upper limit upon the length of the "original datagram"
field. However, each vendor will decide how many octets to include.
Those wishing to be backward compatible with non-compliant TRACEROUTE
implementations will include exactly 128 octets. Those not requiring
compatibility with non-compliant TRACEROUTE applications may include
more octets.
5.4. Compliant Application Receives ICMP Message with No Extensions
When a compliant application receives an ICMP message, it examines
the length attribute that is associated with the "original datagram"
field. If the length attribute is zero, the compliant application
MUST determine that the message contains no extensions.
5.5. Compliant Application Receives ICMP Message with Non-compliant
Extensions
When a compliant application receives an ICMP message, it examines
the length attribute that is associated with the "original datagram"
field. If the length attribute is zero, the compliant application
MUST determine that the message contains no extensions. In this
case, that determination is technically correct, but not backwards
compatible with the non-compliant implementation that originated the
ICMP message.
So, to ease transition yet encourage compliant implementation,
compliant TRACEROUTE implementations MAY include a non-default
operation mode to also interpret non-compliant responses.
Specifically, when a TRACEROUTE application operating in non-
compliant mode receives an ICMP message that contains 144 octets or
more in its payload and does not specify a length attribute, it will
parse for a valid extension header beginning at octet 137. If the
application detects a valid version and checksum, it will treat the
following octets as an extension structure.
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6. The ICMP Extension Structure
This memo proposes an optional ICMP Extension Structure that can be
appended to any ICMP message, except for those that are disqualified
in Section 4.5 of this document.
The Extension Structure contains exactly one Extension Header
followed by one or more objects. Having received an ICMP message
with extensions, application software MAY process selected objects
while ignoring others. The presence of an unrecognized object does
not imply that an ICMP message is malformed.
As stated in RFC 792, the total length of the ICMP message, including
extensions, MUST NOT exceed 576 octets. Figure 5 depicts the ICMP
Extension Header.
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| (Reserved) | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: ICMP Extension Header
The fields of the ICMP Extension Header are as follows:
Version: 4 bits
ICMP extension version number. This is version 2.
Reserved: 12 bits
Must be set to 0.
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.
7. ICMP Extension Objects
Each extension object contains one or more 32-bit words, representing
an object header and payload. All object headers share a common
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format. Figure 6 depicts the Object Header and payload.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| // (Object payload) // |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Object Header and Payload
An object header has the following fields:
Length: 16 bits
Length of the object, measured in octets, including the object
header and object payload.
Class-Num: 8 bits
Identifies object class.
C-Type: 8 bits
Identifies object sub-type.
8. Security Considerations
Upon receipt of an ICMP message, application software must check it
for syntactic correctness. The extension checksum must be verified.
Improperly specified length attributes and other syntax problems may
result in buffer overruns.
This memo does not define the conditions under which a router sends
an ICMP message. Therefore, it does not expose routers to any new
denial of service attacks. Routers may need to limit the rate at
which ICMP messages are sent.
9. IANA Considerations
The ICMP Extension Object header contains two 8-bit fields: The
Class-Num identifies the object class, and the C-Type identifies the
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class sub-type. Sub-type values are defined relative to a specific
object class value, and are defined per-class.
IANA should establish a registry of ICMP extension objects classes
and class sub-types. There are no values assigned within this
document to maintain. Object classes 0xF7 - 0xFF are reserved for
private use. Object class values are assignable on a first-come-
first-serve. The policy for assigning sub-type values should be
defined in the document defining new class values.
10. Acknowledgments
Thanks to Joe Touch for his comments regarding this draft.
11. References
11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792,
September 1981.
[3] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[4] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812,
June 1995.
11.2. Informative References
[5] Atlas, A., "ICMP Extensions for Unnumbered Interfaces",
draft-atlas-icmp-unnumbered-01 (work in progress), March 2006.
[6] Mogul, J. and J. Postel, "Internet Standard Subnetting
Procedure", STD 5, RFC 950, August 1985.
[7] Deering, S., "ICMP Router Discovery Messages", RFC 1256,
September 1991.
[8] Malkin, G., "Traceroute Using an IP Option", RFC 1393,
January 1993.
[9] Simpson, W., "ICMP Domain Name Messages", RFC 1788, April 1995.
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[10] Karn, P. and W. Simpson, "ICMP Security Failures Messages",
RFC 2521, March 1999.
[11] Kempf, J., "Instructions for Seamoby and Experimental Mobility
Protocol IANA Allocations", RFC 4065, July 2005.
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Authors' Addresses
Ronald P. Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
US
Email: rbonica@juniper.net
Der-Hwa Gan
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: dhg@juniper.net
Pekka Nikander
Ericsson Research Nomadic Lab
JORVAS FIN-02420
Finland
Email: pekka.nikander@nomadiclab.com
Daniel C. Tappan
Cisco Systems, Inc.
250 Apollo Drive
Chelmsford, MA 01824
US
Email: tappan@cisco.com
Carlos Pignataro
Cisco Systems, Inc.
7025 Kit Creek Road
Research Triangle Park, N.C. 27709
US
Email: cpignata@cisco.com
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Bonica, et al. Expires December 11, 2006 [Page 19]
