Internet Engineering Task Force R. Shakir
Internet-Draft BT
Intended status: Informational December 27, 2012
Expires: June 30, 2013
Operational Requirements for Enhanced Error Handling Behaviour in BGP-4
draft-ietf-grow-ops-reqs-for-bgp-error-handling-06
Abstract
BGP is utilised as a key intra- and inter-autonomous system routing
protocol in modern IP networks. The failure modes, as defined by the
original protocol standards, are based on a number of assumptions
around the impact of session failure. Numerous incidents both in the
global Internet routing table and within service provider networks
have been caused by strict handling of a single invalid UPDATE
message causing large-scale failures in one or more autonomous
systems.
This memo describes the current use of BGP within service provider
networks, and outlines a set of requirements for further work to
enhance the mechanisms available to a BGP implementation when
erroneous data is detected. Whilst this document does not provide
specification of any standard, it is intended as an overview of a set
of enhancements to BGP to improve the protocol's robustness to suit
its current deployment.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on June 30, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
Shakir Expires June 30, 2013 [Page 1]
Internet-Draft Requirements for BGP Error Handling December 2012
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Role of BGP-4 in Service Provider Networks . . . . . . . . 4
3. Critical and Non-Critical Errors . . . . . . . . . . . . . . . 7
4. Error Handling for Non-Critical Errors . . . . . . . . . . . . 9
4.1. NLRI-level Error Handling Requirements . . . . . . . . . . 9
4.2. Recovering RIB Consistency following NLRI-level Error
Handling . . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Error Handling for Critical Errors . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
9.2. Informational References . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
Shakir Expires June 30, 2013 [Page 2]
Internet-Draft Requirements for BGP Error Handling December 2012
1. Requirements Language
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].
Shakir Expires June 30, 2013 [Page 3]
Internet-Draft Requirements for BGP Error Handling December 2012
2. Problem Statement
BGP has become a key intra- and inter-domain routing protocol,
deployed within both the Internet and private networks. The
increased reliance on the protocol has resulted in increased demand
for robustness - with the error handling behaviour defined in
[RFC4271] having been shown to have caused numerous incidents within
live network deployments. This document provides an overview of the
current deployment cases for BGP-4, and define a set of requirements
(from the perspective of a network operator) for enhancing error
handling within the protocol.
2.1. Role of BGP-4 in Service Provider Networks
BGP was designed as an inter-autonomous system (AS) routing protocol.
Many of the error handling mechanisms within the protocol are defined
in order to be guarantee consistency, and correctness of information
between two neighbouring speakers. The assumption is made that each
AS operates with many adjacencies, each propagating a relatively
small amount of routing information. Through focusing on information
consistency, the protocol specification prefers failure of an
individual routing adjacency to maintaining reachability to all NLRI
received from a particular neighbour, with the expectation that
alternate, less direct, paths can be selected where a failure occurs.
The assumptions of the nature of BGP deployments resulted in the
specification made in [RFC4271] whereby the receipt of an erroneous
UPDATE message is reacted to by sending a NOTIFICATION message, and
tearing down the adjacency with the remote speaker from whom the
error was observed.
Historically, a network would deploy an interior gateway protocol
(IGP) to carry infrastructure and customer routes, and utilise an
external gateway protocol (EGP) such as BGP to propagate routes to
other autonomous systems. However, BGP's deployments have evolved
with the growth of IP-based services. To ensure route convergence
within an AS is within acceptable time bounds the amount of
information within the IGP has been minimised (typically to only
infrastructure routes). iBGP is then utilised to carry both internal,
customer and external routes within an AS. As such, this has
resulted in BGP having become an IGP, with traditional IGPs providing
only reachability between nodes within the AS for packet forwarding
and to establish iBGP sessions. This change in role within the
overall architecture of an AS has resulted in an increased robustness
requirement for BGP, with the expectation of a similar level of
robustness to that of an IGP being set. The loss of an iBGP session
can result in significant levels of unreachability internally to an
AS, especially since there are typically limited (when compared to
the Internet) signalling and forwarding paths available.
Shakir Expires June 30, 2013 [Page 4]
Internet-Draft Requirements for BGP Error Handling December 2012
In parallel with this change of deployment, the volume and nature of
the information carried within BGP has also changed. BGP has become
the ubiquitous means through which service information can be
propagated between devices. For instance, being utilised to carry
IP/MPLS service information such as Layer 3 IP VPN routes [RFC4364] ,
and Layer 2 Virtual Private LAN Service device membership [RFC4761].
Since these extensions to the protocol allow signalling of multiple
services (represented by address families within BGP), and multiple
customer topologies (i.e., subsets of routes within each address
family) via the BGP protocol, the impact of session failure is
increased. The tear down of a single BGP session can result in a
complete outage to all customer services signalled via the session,
even where the triggering event is related to only one service or
topology being carried - reflecting a disproportional impact to all
other services and routing topologies.
The convergence of services to IP, and BGP's changing deployment has
resulted in a significant growth in the volume of routing information
carried in the protocol. In numerous networks, the RIB size of
individual BGP speakers can be of the order of millions of paths.
Particularly large RIBs are observed at BGP speakers performing
aggregation and border roles (such as ASBR, or route reflector
hierarchies). This increased volume of routes results not only in a
significant number of services being impacted during a protocol
failure, but also increases the time to recovery after re-
establishing a BGP session. The time taken to learn, compute and
distribute new paths increases the impact of failures on services
carried by the network - adding further weight to the requirement to
avoid failures, or limit the extent of their impact. Furthermore,
the impact of individual session failures is increased due to the
existence of a relatively small number of highly-critical BGP
sessions within Internet and multi-service network deployments.
These sessions propagate a high-proportion of the reachability
information - for instance, providing an Internet AS with the global
routing table from upstream providers, or connecting IP/MPLS Provider
Edge devices to route reflector hierarchies from which they are
signalled reachability for services connected elsewhere within the
routing domain. In both cases, the failure of these sessions can
result in a significant outage to customer services.
For the current deployments of BGP, the behaviour described in
[RFC4271] related to handling errors in UPDATE messages is
suboptimal, and results in significant disruption to services in
modern network deployments. This document defines a set of
requirements for protocol developments, and revisions to [RFC4271] to
address these concerns through a set of generalised definitions. It
should be noted that the scope of these requirements is limited to
the handling of UPDATE messages as, at the time of writing, there is
Shakir Expires June 30, 2013 [Page 5]
Internet-Draft Requirements for BGP Error Handling December 2012
no operational requirement to amend the means by which error handling
in session establishment, or liveliness detection are performed.
Shakir Expires June 30, 2013 [Page 6]
Internet-Draft Requirements for BGP Error Handling December 2012
3. Critical and Non-Critical Errors
As described in Section 2.1, the error handling behaviour described
in [RFC4271] is applied at a per-session level, affecting all NLRI
signalled via the adjacency on which an erroneous message is
observed. In order to reduce the impact of error handling to those
NLRI affected by an erroneous UPDATE, a BGP speaker MUST limit the
error handling mechanisms implemented to those NLRI contained within
an erroneous UPDATE message where it is possible to do so. Clearly,
some errors within the formation of BGP UPDATE messages may result in
it being impossible to reliably extract NLRI from the received
message, and hence the same error handling procedures may not apply.
There is therefore a requirement to classify errors based on their
impact to the BGP UPDATE message, hence messages whereby the NLRI
attribute cannot be extracted or parsed are referred to throughout
this document as Critical errors. These Critical errors are limited
to:
o UPDATE Message Length errors - where the specified UPDATE message
length is inconsistent with the sum of the Total Path Attribute
and Withdrawn Routes length. These errors relate to message
packing or framing, and result in cases whereby the NLRI attribute
cannot be correctly extracted from the message.
o Errors parsing the NLRI attribute of an UPDATE message - where the
contents of the IPv4 Unicast Advertised or Withdrawn Routes
attributes, or multi-protocol BGP NLRI attributes (MP_REACH_NLRI
and/or MP_UNREACH_NLRI as defined in [RFC2858]), cannot be
successfully parsed.
In the case of Critical errors is expected that error handling is
applied at a session level as per Section 5 of this document.
All errors whereby the contained NLRI can be extracted, are referred
to as Non-Critical. It is expected that the following cases fall
within this category:
o Zero or invalid length errors in path attributes, excluding those
containing NLRI, or where the length of all path attributes
contained within the UPDATE does not correspond to the total path
attribute length.
o Messages where invalid data or flags are contained in a path
attribute that does not relate to the NLRI.
o UPDATE messages missing mandatory attributes, unrecognised non-
optional attributes, or those that contain duplicate or invalid
attributes (be they unsupported, or unexpected).
Shakir Expires June 30, 2013 [Page 7]
Internet-Draft Requirements for BGP Error Handling December 2012
o Those messages where the NEXT_HOP, the MP_REACH_NLRI next-hop
values are missing, zero-length, or invalid for the relevant
address family.
For these Non-Critical errors, the NLRI-targeted error handling
requirements described in Section 4 should be followed.
In order to maximise the number of cases whereby the NLRI attributes
can be reliably extracted from a received message, where a BGP
speaker supports multi-protocol extensions, the MP_REACH_NLRI and
MP_UNREACH_NLRI attributes SHOULD be utilised for all address
families (including IPv4 Unicast) and these attributes should be the
first attribute contained within the UPDATE message.
Where attributes are introduced by future extensions to the BGP
protocol the error handling behaviour applied MUST be assumed that
applied to Non-Critical errors, unless otherwise specified within the
per-extension memo, or the attribute relates directly to carrying
NLRI. Authors of future BGP extensions SHOULD specify the error
handling behaviour required for new attributes in terms of the
classification into a Critical or Non-Critical error on a per-
attribute error basis.
Shakir Expires June 30, 2013 [Page 8]
Internet-Draft Requirements for BGP Error Handling December 2012
4. Error Handling for Non-Critical Errors
4.1. NLRI-level Error Handling Requirements
When a Non-Critical error is detected within an UPDATE message a BGP
speaker MUST NOT send a NOTIFICATION message to the remote neighbour.
Instead, the NLRI contained within the message MUST be considered as
no longer viable until they are updated by a subsequent UPDATE
message, thus treating the NLRI as withdrawn as per the treat-as-
withdraw mechanism described in [I-D.chen-ebgp-error-handling].
Network operators SHOULD recognise that where such behaviour is
implemented black-holing or looping of traffic may occur in the
period between the NLRI being treated as withdrawn, and subsequent
updates, dependent upon the routing topology. It SHOULD be noted
that such periods of RIB inconsistency (where one speaker has
advertised a prefix, which has been treated as withdrawn by the
receiving speaker) may be relatively long lived, based on situations
such as an erroneous implementation at the receiver, or the error
occurring within an optional, transitive attribute not examined by
the advertising device. In order to allow operators to select
sessions on which this risk of inconsistency is acceptable, an
implementation SHOULD provide means by which NLRI-level error
handling for Non-Critical errors can be disabled on a per-session
basis.
Since the Non-Critical error handling required within this section
results in no NOTIFICATION message being transmitted, the fact that
an error has occurred and hence there may be inconsistency between
the local and remote BGP speaker MUST be flagged to the network
operator through standard operational interfaces (e.g., SNMP,
syslog). The information highlighted MUST include the NLRI
identified to be contained within the error message, and SHOULD
contain a exact copy of the received message for further analysis.
In order that the operator of the BGP speaker from whom an erroneous
UPDATE message has been advertised is aware of the fact that some
NLRI advertised to the remote speaker have been considered withdrawn
due to being contained within an erroneous UPDATE, a BGP speaker
SHOULD support mechanisms to report the occurrence of Non-Critical
error handling to the remote speaker. The receiving speaker SHOULD
transmit the NLRI contained within the erroneous message to the
advertising speaker. An exact copy of the received UPDATE message
SHOULD also be sent.
The exchange of information related to events occurring as a result
of BGP messages is not currently supported by any extension to the
protocol. Clearly, where the two speakers reside within the same
Shakir Expires June 30, 2013 [Page 9]
Internet-Draft Requirements for BGP Error Handling December 2012
administrative domain, shared logging infrastructure can be utilised
to identify the root cause of errors, however, in many cases
neighbouring BGP speakers reside within separate administrative
domains (e.g., are ASBRs for Internet or private networks). In this
case, mechanisms allowing transmission in-band to the BGP session
SHOULD be utilised (e.g., the OPERATIONAL message described in
[I-D.ietf-idr-operational-message]). Such an in-band channel is
preferred based on the BGP session representing a pre-established
trusted channel which is related to a specific BGP-speaking device
within a network. It is expected that the overall system scalability
of a BGP speaker is improved through utilising the existing channel,
rather than incurring overhead for maintaining many additional
logging-specific protocol sessions for relatively infrequent
messaging events when errors occur. However, the extensions
providing such a channel MUST consider their impact to base BGP
protocol functions such as the transmission of UPDATE or KEEPALIVE
messages, and SHOULD limit the volume of messaging to direct
reactions to Non-Critical errors occurring. These considerations
SHOULD be made in order to ensure that no compromise is made to the
security, scalability and robustness of BGP. Where additional BGP
monitoring information that is not suitable to be carried in-band is
required, out-of-band mechanisms such as the BMP protocol described
in [I-D.ietf-grow-bmp] could be utilised to provide further
information relating to erroneous messages.
4.2. Recovering RIB Consistency following NLRI-level Error Handling
Following NLRI being treated as withdrawn due to Non-Critical error
handling, inconsistencies exist between the Adj-RIB-Out of the
advertising BGP speaker, and the Adj-RIB-In of the receiving device.
These inconsistencies may result in forwarding loops or blackholing
of traffic in some routing topologies. In order to ensure that such
cases can be recovered from a means by which a validation and
recovery of consistency can be achieved SHOULD be provided to an
operator. This function may be provided through enhancing the ROUTE-
REFRESH [RFC2918] mechanism to add means to identify the beginning
and end of a replay of the entire Adj-RIB-Out of the advertising
speaker (as per the suggestion in
[I-D.ietf-idr-bgp-enhanced-route-refresh]).
As Non-Critical error handling is localised to the NLRI contained
within the erroneous UPDATE message, a targeted recovery mechanism
MAY be provided allowing a speaker to request re-advertisement of a
particular subset of the Adj-RIB-Out. Where such targeted refresh
functions are available, they SHOULD be preferred to mechanisms
requesting re-advertisement of the whole Adj-RIB-Out based on their
more limited use of CPU and network resources.
Shakir Expires June 30, 2013 [Page 10]
Internet-Draft Requirements for BGP Error Handling December 2012
A BGP speaker may automatically trigger recovery mechanisms such as
those described in this section following the receipt of an erroneous
UPDATE message identified as Non-Critical to expedite recovery. It
should be noted that if automatic recovery mechanisms trigger only
re-advertisement of an identical erroneous message, they are likely
to be ineffective. Additionally, where the best-path to be
advertised by remote speaker changes, this will be advertised
directly, without a requirement for a request from the receiver.
However, in some cases, RIB consistency recovery mechanisms may
prompt alternate UPDATE message packing, and hence allow quicker
recovery. Where such mechanisms are implemented, mechanisms focused
to smaller sets of NLRI SHOULD be preferred over those requesting the
entire RIB. In addition, such mechanisms SHOULD have dampening
mechanisms to ensure that their impact to computational and network
resources is limited.
Shakir Expires June 30, 2013 [Page 11]
Internet-Draft Requirements for BGP Error Handling December 2012
5. Error Handling for Critical Errors
Where an UPDATE message containing a Critical error is received,
since the NLRI cannot be extracted, error handling mechanisms must be
applied at the per-session level. In order to limit the impact to
network operation, these session-level mechanisms MUST be applied in
a manner which allows the paths NLRI received from the remote speaker
to continue to be utilised for forwarding during the session reset
and re-establishment. It is envisaged that this requirement may be
met through extension of the BGP Graceful Restart mechanism
([RFC4724]) to be triggered by NOTIFICATION messages indicating the
occurrence of a Critical error. Such an extension allows a restart
of the TCP and BGP sessions between two speakers, in a similar manner
to the current session restart behaviour triggered by a NOTIFICATION
message. In order to maximise the level of re-initialisation which
occurs during such a restart triggered by a Critical error, BGP
speakers MAY re-initialise memory structures related to the
Adj-RIB-In and Adj-RIB-Out associated with the session on which the
erroneous UPDATE was observed.
Where such a restart event occurs, the continued liveliness of the
remote device MAY be verified by BGP KEEPALIVE packets or other OAM
functions such as Bidirectional Forwarding Detection ([RFC5880]). In
cases where the observed Critical BGP error is indicative of a wider
device failure of the remote speaker, it is expected that a BGP
sessions will not re-establish correctly. Each BGP speaker SHOULD
maintain a limited time window in which session restart is expected
in order to mitigate this possibility.
When a Critical error occurs, the network operator MUST be made aware
of its occurrence through local logging mechanisms (e.g., SNMP traps
or syslog). The BGP speaker receiving an UPDATE message identified
as a Critical error MUST log its occurrence and a copy of the UPDATE
message. Where a inter-device messaging mechanism is implemented (as
discussed in Section Section 4.1) a copy of the erroneous UPDATE
message SHOULD be transmitted to the remote speaker. Both BGP
speakers MUST indicate to an operator the cause of a session restart
was a Critical error in an UPDATE message.
Since repeated critical errors (and session restarts) may have an
impact in overall device scaling if the failure condition is not
resolved by session restart, a BGP speaker MAY choose to revert to
the session tear down behaviour described in the base BGP
specification. This reversion SHOULD only be utilised after a number
of attempts which SHOULD be controllable by the network operator.
Where a session is shut down, the implementation MAY utilise a back-
off from session restart attempts (as per the IdleHoldTimer described
in the BGP FSM [RFC4271]). Where reversion to tearing down the BGP
Shakir Expires June 30, 2013 [Page 12]
Internet-Draft Requirements for BGP Error Handling December 2012
session is performed, a speaker SHOULD limit the impact of
withdrawing prefixes from downstream speakers where possible. It is
envisaged that this can be achieved by utilising a mechanism such as
the BGP Graceful Shutdown procedure as described in
[I-D.ietf-grow-bgp-gshut].
Shakir Expires June 30, 2013 [Page 13]
Internet-Draft Requirements for BGP Error Handling December 2012
6. IANA Considerations
This memo includes no request to IANA.
Shakir Expires June 30, 2013 [Page 14]
Internet-Draft Requirements for BGP Error Handling December 2012
7. Security Considerations
The requirements outlined in this document provide mechanisms which
limit the overall impact of the response to an error in a BGP UPDATE
message. This is of benefit to the security of a BGP speaker.
Without these mechanisms, where erroneous UPDATE messages relating to
a single NLRI entry can be propagated to a BGP speaker, all other
NLRI carried via the same session are affected by the resulting
session tear-down. This may result in an AS being isolated from
particular routing domains (such as the Internet) should an UPDATE
message be propagated via targeted specific paths. It is envisaged
by reducing the impact of the reaction of the receiving speaker to
these messages, the isolation can be constrained to specific sets of
NLRI, or a specific topology.
A number of the mechanisms meeting the requirements specified within
the document (particularly those relating to operational monitoring)
may raise further security concerns. Such concerns will be addressed
during the specification of these mechanisms.
Shakir Expires June 30, 2013 [Page 15]
Internet-Draft Requirements for BGP Error Handling December 2012
8. Acknowledgements
The author would like to thank the following network operators for
their insight, and valuable input into defining the requirements for
a variety of deployments of the BGP protocol: Shane Amante, Bruno
Decraene, Rob Evans, David Freedman, Wes George, Tom Hodgson, Sven
Huster, Jonathan Newton, Neil McRae, Thomas Mangin, Tom Scholl and
Ilya Varlashkin.
In addition, many thanks are extended to Jeff Haas, Wim Hendrickx,
Tony Li, Alton Lo, Keyur Patel, John Scudder, Adam Simpson and Robert
Raszuk for their expertise relating to implementations of the BGP
protocol.
Shakir Expires June 30, 2013 [Page 16]
Internet-Draft Requirements for BGP Error Handling December 2012
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
"Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.
[RFC2918] Chen, E., "Route Refresh Capability for BGP-4", RFC 2918,
September 2000.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4724] Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
January 2007.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling",
RFC 4761, January 2007.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
9.2. Informational References
[I-D.chen-ebgp-error-handling]
Chen, E., Mohapatra, P., and K. Patel, "Revised Error
Handling for BGP Updates from External Neighbors",
draft-chen-ebgp-error-handling-01 (work in progress),
September 2011.
[I-D.ietf-grow-bgp-gshut]
Francois, P., Decraene, B., Pelsser, C., Patel, K., and C.
Filsfils, "Graceful BGP session shutdown",
draft-ietf-grow-bgp-gshut-04 (work in progress),
October 2012.
[I-D.ietf-grow-bmp]
Scudder, J., Fernando, R., and S. Stuart, "BGP Monitoring
Protocol", draft-ietf-grow-bmp-07 (work in progress),
October 2012.
Shakir Expires June 30, 2013 [Page 17]
Internet-Draft Requirements for BGP Error Handling December 2012
[I-D.ietf-idr-bgp-enhanced-route-refresh]
Patel, K., Chen, E., and B. Venkatachalapathy, "Enhanced
Route Refresh Capability for BGP-4",
draft-ietf-idr-bgp-enhanced-route-refresh-03 (work in
progress), December 2012.
[I-D.ietf-idr-operational-message]
Freedman, D., Raszuk, R., and R. Shakir, "BGP OPERATIONAL
Message", draft-ietf-idr-operational-message-00 (work in
progress), March 2012.
Shakir Expires June 30, 2013 [Page 18]
Internet-Draft Requirements for BGP Error Handling December 2012
Author's Address
Rob Shakir
BT
pp C3L, BT Centre
81, Newgate Street
London EC1A 7AJ
UK
Email: rob.shakir@bt.com
URI: http://www.bt.com/
Shakir Expires June 30, 2013 [Page 19]
