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<rfc category="std" xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-idr-bgp-optimal-route-reflection-28" number="9107" ipr="trust200902" obsoletes="" updates="" submissionType="IETF"
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<front>
    <title abbrev="bgp-optimal-route-reflection"> abbrev="BGP Optimal Route Reflection">
BGP Optimal Route Reflection (BGP ORR)
</title>
    <seriesInfo name="RFC" value="9107"/>
    <author fullname='Robert Raszuk' initials='R' surname='Raszuk' fullname="Robert Raszuk" initials="R" surname="Raszuk" role="editor">
      <organization>NTT Network Innovations</organization>
      <address>
        <email>robert@raszuk.net</email>
      </address>
    </author>
    <author initials="B" surname="Decraene" fullname="Bruno Decraene" role="editor">
      <organization>Orange</organization>
      <address>
        <email>bruno.decraene@orange.com</email>
      </address>
    </author>
    <author initials="C" surname="Cassar" fullname="Christian Cassar">
      <address>
        <email>cassar.christian@gmail.com</email>
      </address>
    </author>
    <author initials="E" surname="Aman" fullname="Erik Aman">
	<organization></organization>
      <organization/>
      <address>
        <email>erik.aman@aman.se</email>
      </address>
    </author>
    <author initials="K" surname="Wang" fullname="Kevin Wang">
      <organization>Juniper Networks</organization>
      <address>
        <postal>
          <street>10 Technology Park Drive</street>
          <city>Westford</city>
          <region>MA</region>
          <code>01886</code>
		<country>USA</country>
          <country>United States of America</country>
        </postal>
        <email>kfwang@juniper.net</email>
      </address>
    </author>
    <date year="2021" /> month="August"/>
    <area>Routing</area>
    <workgroup>IDR Working Group</workgroup>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
    <keyword>IDR</keyword>
    <abstract>
      <t>This document defines an extension to BGP route reflectors. On route reflectors,
BGP route selection is modified in order to choose the best route from the standpoint
of their clients, rather than from the standpoint of the route reflectors. reflectors themselves. Depending
on the scaling and precision requirements, route selection can be specific for one
client, common for a set of clients clients, or common for all clients of a route reflector.
This solution is particularly applicable in deployments using centralized route
reflectors, where choosing the best route based on the route reflector's IGP location
is suboptimal. This  facilitates, for example, best a "best exit point point" policy (hot ("hot potato
routing).</t>
routing").</t>
      <t>The solution relies upon all route reflectors learning all paths which that
are eligible for consideration. BGP Route Selection route selection is performed in the route
reflectors based on the IGP cost from configured locations in the link state link-state IGP.</t>
    </abstract>
  </front>
  <middle>
    <section title="Introduction"> numbered="true" toc="default">
      <name>Introduction</name>
      <t>There are three types of BGP deployments within Autonomous Systems (ASes) today: full mesh,
confederations
confederations, and route reflection. BGP route reflection <xref target="RFC4456" /> format="default"/> is
the most popular way to distribute BGP routes between BGP speakers belonging to the same
Autonomous System.
AS. However, in some situations, this method suffers from non-optimal
path selection. </t>
      <t> <xref target="RFC4456" /> format="default"/> asserts that, because the IGP cost to a given point in
the network will vary across routers,
 "the route reflection approach may not yield the
same route selection result as that of the full Internal BGP (IBGP) IBGP mesh approach." ("IBGP" stands for "Internal BGP".) One
practical implication of this fact is that the deployment of route reflection may thwart
the ability to achieve hot "hot potato routing. routing". Hot potato routing attempts to direct traffic to the closest Autonomous System (AS) AS exit point in cases where no higher priority higher-priority policy
dictates otherwise. As a consequence of the route reflection method, the choice of exit
point for a route reflector and its clients will be the exit point that is optimal for
the route reflector - -- not necessarily the one that is optimal for its clients. </t>

<t> Section 11 of <xref
      <t><xref target="RFC4456" /> sectionFormat="of" section="11"/> describes a deployment approach and a set
of constraints which, that, if satisfied, would result in the deployment of route reflection
yielding the same results as the IBGP full mesh approach. This deployment approach makes
route reflection compatible with the application of a hot potato routing policy. In
accordance with these design rules, route reflectors have often been deployed in the
forwarding path and carefully placed on the boundaries between the Point of Presence (POP) to core boundaries.</t> and the network core.</t>
      <t>The evolving model of intra-domain network design has enabled deployments of route
reflectors outside the forwarding path. Initially Initially, this model was only employed for new
services, e.g., IP VPNs <xref target="RFC4364" />, however format="default"/>; however, it has been gradually
extended to other BGP services, including the IPv4 and IPv6 Internet. In such
environments, a hot potato routing policy remains desirable.</t>
      <t>Route reflectors outside the forwarding path can be placed on the boundaries between the POP to core
boundaries, and the network core,
but they are often placed in arbitrary locations in the core of large
networks.</t>
      <t>Such deployments suffer from a critical drawback in the context of BGP Route Selection:
A route selection:
a route reflector with knowledge of multiple paths for a given route will typically pick
its best path and only advertise that best path to its clients. If the best path for a
route is selected on the basis of an IGP tie-break, the path advertised will be the exit
point closest to the route reflector. However, the clients are in a different place in
the network topology than the route reflector. In networks where the route reflectors are
not in the forwarding path, this difference will be even more acute.</t>
      <t>In addition, there are deployment scenarios where service providers want to have more
control in choosing the exit points for clients based on other factors, such as traffic
type, traffic load, etc. This further complicates the issue and makes it less likely for
the route reflector to select the best path from the client's perspective. It follows
that the best path chosen by the route reflector is not necessarily the same as the path
which
that would have been chosen by the client if the client had considered the same set of
candidate paths as the route reflector.</t>
    </section>
    <section title="Terminology"> numbered="true" toc="default">
      <name>Terminology</name>
<t>This memo makes use of the terms defined in <xref target="RFC4271"/> and <xref target="RFC4456"/>.</t>
       <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
      NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
      "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
       "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>",
       "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>",
       "<bcp14>SHOULD NOT</bcp14>",
       "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
       "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document
       are to be interpreted as described in BCP 14 BCP&nbsp;14
       <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only
       when, they appear in all capitals, as shown here.
	</t> here.</t>
    </section>
    <section title="Modifications numbered="true" toc="default">
      <name>Modifications to BGP Route Selection"> Selection</name>
      <t>The core of this solution is the ability for an operator to specify the IGP location
for which the route reflector calculates interior cost for to the NEXT_HOP. next hop. The IGP
location is defined as a node in the IGP topology, it is identified by an IP address
of this node (e.g., a loopback address), and it may be configured on a per route reflector
per-route-reflector basis, per set of clients, or per client on a per-client basis. Such configuration will allow the
route reflector to select and distribute to a given set of clients routes with the shortest
distance to the next hops from the position of the selected IGP location. This provides
for freedom of related to the route reflector reflector's physical location, location and allows transient or permanent
migration of this network control plane function to an arbitrary location with no
impact to on IP transit.</t>
      <t>The choice of specific granularity (route reflector, set of clients, or client) is
configured by the network operator. An implementation is considered compliant with this
document if it supports at least one such grouping category.</t>
      <t> For purposes of route selection, the perspective of a client can differ from that of
a route reflector or another client in two distinct ways:
<list style="symbols">
  <t> it
</t>
      <ul spacing="normal">
        <li>It has a different position in the IGP topology,</t>
  <t> it topology.</li>
        <li>It can have a different routing policy.</t>
</list> policy.</li>
      </ul>
      <t>
These factors correspond to the issues described earlier. </t>
      <t>This document defines, for BGP Route Reflectors route reflectors <xref target="RFC4456" />, format="default"/>, two changes
to the BGP Route Selection algorithm:

<list style="symbols" >
<t>The route selection algorithm:</t>
      <ul spacing="normal">
        <li>The first change, introduced in <xref target="sec_IGP_cost" />, format="default"/>, is related to the IGP
cost to the BGP Next Hop next hop in the BGP decision process. Decision Process. The change consists of using the IGP
cost from a different IGP location than the route reflector itself.</t>

<t>The itself.</li>
        <li>The second change, introduced in <xref target="sec_multiple" />, format="default"/>, is to extend the
granularity of the BGP decision process, Decision Process, to allow for running multiple decisions processes Decision Processes
using different perspective perspectives or policies.</t>
</list></t> policies.</li>
      </ul>
        <t> A route reflector can implement either or both of the modifications in order to
allow it to choose the best path for its clients that the clients themselves would have
chosen given the same set of candidate paths.</t>
      <t>A significant advantage of these approaches is that the route reflector reflector's clients do
not need to be modified.</t>
      <section title="Route anchor="sec_IGP_cost" numbered="true" toc="default">
        <name>Route Selection from a different Different IGP location" anchor="sec_IGP_cost"> Location</name>
        <t>In this approach, optimal "optimal" refers to the decision where the interior cost of a route is
determined during step e) of <xref Section&nbsp;<xref target="RFC4271" /> section 9.1.2.2 "Breaking section="9.1.2.2"
sectionFormat="bare">"Breaking Ties (Phase 2)". 2)"</xref> of <xref target="RFC4271"/>. It does not apply to path selection preference based on other policy steps
and provisions.</t>
        <t>In addition to the change specified in <xref target="RFC4456" /> section 9, sectionFormat="of" section="9"/>, the text in step e) in <xref target="RFC4271" /> section 9.1.2.2 sectionFormat="of" section="9.1.2.2"/> is modified as follows.</t>

<t>The below text in step e)
<list>
<t>e) Remove

<t>RFC 4271 reads:</t>
<blockquote>
        <dl spacing="normal" indent="4">
        <dt>e)</dt><dd>Remove from consideration any routes with less-preferred
         interior cost.  The interior cost of a route is determined by
         calculating the metric to the NEXT_HOP for the route using the
         Routing Table.</t>
</list></t>

<t>...is replaced by Table.</dd>
        </dl>
</blockquote>
        <t>This document modifies this new text:
<list>
<t>e) Remove text to read:</t>
<blockquote>
        <dl spacing="normal" indent="4">
        <dt>e)</dt><dd>Remove from consideration any routes with less-preferred
         interior cost.  The interior cost of a route is determined by
         calculating the metric from the selected IGP location to the NEXT_HOP for the route
         using the shortest IGP path tree rooted at the selected IGP location.</t>
</list> </t> location.</dd>
        </dl>
</blockquote>
        <t>In order to be able to compute the shortest path tree rooted at the selected IGP
locations, knowledge of the IGP topology for the area/level that includes each of those
locations is needed. This knowledge can be gained with the use of the link state IGP link-state IGP,
such as IS-IS <xref target="ISO10589"/> target="ISO10589" format="default"/> or OSPF <xref target="RFC2328" /> format="default"/>
          <xref target="RFC5340" /> format="default"/>, or via BGP-LS the Border Gateway Protocol - Link State (BGP-LS) <xref target="RFC7752" />. format="default"/>. When specifying the logical
location of a route reflector for a group of clients clients, one or more backup IGP locations
SHOULD
<bcp14>SHOULD</bcp14> be allowed to be specified for redundancy. Further deployment considerations
are discussed in Section 4.</t> <xref target="deployment-cons"/>.</t>
        <section title="Restriction numbered="true" toc="default">
          <name>Restriction when the BGP next hop is Next Hop Is a BGP route"> Route</name>
          <t>In situations where the BGP next hop is a BGP route itself, the IGP metric of a route
used for its resolution SHOULD <bcp14>SHOULD</bcp14> be the final IGP cost to reach such a next hop. Implementations
which
that cannot inform BGP of the final IGP metric to a recursive next hop MUST <bcp14>MUST</bcp14> treat such
paths as least preferred during next hop next-hop metric comparison. comparisons. However, such paths MUST <bcp14>MUST</bcp14>
still be considered valid for BGP Phase 2 Route Selection.</t> route selection.</t>
        </section>
      </section>
      <section title="Multiple Route Selections" anchor="sec_multiple">

<t>BGP anchor="sec_multiple" numbered="true" toc="default">
        <name>Multiple Route Reflector Selections</name>
        <t>A BGP route reflector as per <xref target="RFC4456" /> format="default"/> runs a single BGP Decision
Process. BGP Optimal route reflection Route Reflection (BGP ORR) may require multiple BGP Decision Processes or
subsets of the Decision Process in order to consider different IGP locations or
BGP policies for different sets of clients. This is very similar to what is defined
in <xref target="RFC7947" /> section 2.3.2.1.</t> sectionFormat="comma" section="2.3.2.1"/>.</t>
        <t> If the required routing optimization is limited to the IGP cost to the BGP
Next-Hop,
next hop, only step e) and subsequent steps as defined in
<xref target="RFC4271" />
section 9.1.2.2, needs sectionFormat="comma" section="9.1.2.2"/> need to be run multiple times.</t>
        <t> If the routing optimization requires the use of different BGP policies for
different sets of clients, a larger part of the decision process Decision Process needs to be run
multiple times, up to the whole decision process Decision Process as defined in section 9.1 of <xref target="RFC4271" />. sectionFormat="of" section="9.1"/>. This is is, for example example, the case when there is a need to
use different policies to compute different degree degrees of preference during Phase 1.
This is needed for use cases involving traffic engineering or dedicating certain
exit points for certain clients. In the latter case, the user may specify and apply
a general policy on the route reflector for a set of clients. Regular path selection,
including IGP perspective perspectives for a set of clients as per <xref target="sec_IGP_cost" />, format="default"/>,
is then applied to the candidate paths to select the final paths to advertise to the
clients. </t>

<t> A route reflector can implement either or both of the modifications in order to
allow it to choose the best path for its clients that the clients themselves would have
chosen given the same set of candidate paths.</t>
      </section>
    </section>
    <section title="Deployment Considerations"> anchor="deployment-cons" numbered="true" toc="default">
      <name>Deployment Considerations</name>
      <t>BGP Optimal Route Reflection ORR provides a model for integrating the client client's
perspective into the BGP Route Selection decision function route selection Decision Process for route reflectors.
More specifically, the choice of BGP path takes into account either the IGP
cost between the client and the NEXT_HOP next hop (rather than the IGP cost from the
route reflector to the NEXT_HOP) next hop) or other user configured user-configured policies.</t>
      <t>The achievement of optimal routing between clients of different clusters
relies upon all route reflectors learning all paths that are eligible for
consideration. In order to satisfy this requirement, BGP add-path ADD-PATH
<xref target="RFC7911" /> format="default"/> needs to be deployed between route reflectors. </t>
      <t>This solution can be deployed in traditional hop-by-hop forwarding
networks as well as in end-to-end tunneled environments. To avoid routing
loops in networks with multiple route reflectors and hop-by-hop forwarding
without encapsulation, it is essential that the network topology be carefully
considered in designing a route reflection topology (see also Section 11 of <xref target="RFC4456" />).</t> sectionFormat="of" section="11"/>).</t>
      <t>As discussed in section 11 of <xref target="RFC4456" />, sectionFormat="of" section="11"/>, the IGP locations
of BGP route reflectors is are important and has have routing implications. This
equally applies to the choice of the IGP locations configured on optimal route
reflectors. If a backup location is provided, it is used when the primary IGP
location disappears from the IGP (i.e. (i.e., fails). Just like the failure of a RR route reflector <xref target="RFC4456" />, format="default"/>, it may result in changing the paths selected and
advertised to the clients clients, and in general general, the post-failure paths are expected to
be less optimal. This is dependent on the IGP topologies and the IGP distance
between the primary and the backup IGP locations: the smaller the distance distance, the
smaller the potential impact.</t>

<t>After
      <t>
After selecting N suitable IGP locations, an operator may let one or multiple
route reflectors handle can choose to enable route
selection for all of them. them on all or on a subset of their route reflectors. The
operator may alternatively deploy one single or multiple (backup case) route reflector
reflectors for each IGP location or create any design in between.  This
choice may depend on the operational model (centralized vs vs. per region), an acceptable
blast radius in the case of failure, an acceptable number of IBGP sessions for the mesh between the route reflectors,
performance performance, and configuration granularity of the equipment.</t>
      <t>With this approach, an ISP can effect a hot potato routing policy
even if route reflection has been moved out of the forwarding plane, plane and
hop-by-hop forwarding has been replaced by end-to-end MPLS or IP
encapsulation. Compared with a deployment of ADD-PATH on all routers, BGP
Optimal Route Reflection (ORR) ORR
reduces the amount of state which that needs to
be pushed to the edge of the network in order to perform hot potato routing.</t>
      <t>Modifying the IGP location of BGP ORR does not interfere with policies
enforced before IGP tie-breaking (step e) of
<xref target="RFC4271" /> section
9.1.2.2 sectionFormat="comma" section="9.1.2.2"/>) in the BGP Decision Process.</t>
      <t>Calculating routes for different IGP locations requires multiple Shortest
Path First (SPF) calculations and multiple (subsets of) BGP Decision Processes,
which requires Processes.
This scenario calls for more computing resources. This document allows for different
granularity
granularity, such as one Decision Process per route reflector, per set of clients clients,
or per client. A more fine-grained granularity may translate into more optimal
hot potato routing at the cost of more computing power. Selecting Choosing to configure
an IGP location per client has the highest precision precision, as each client can be
associated with their ideal (own) IGP location.  However, doing so may have an
impact on the performance (as explained above).  Using an IGP location per set
of clients implies a loss of precision, precision but reduces the impact on the performance
of the route reflector.  Similarly, if an IGP location is selected for the whole
routing instance, the lowest precision is achieved, but the performance impact on performance
is minimal. In the last mode of operation (where an IGP location is selected for the whole routing instance), both precision as well as perfomance and performance
metrics are equal to same metrics when using route reflection as described in
<xref target="RFC4456" /> without ORR extension. format="default"/>. The ability to run fine-grained computations depends on the platform/hardware
deployed, the number of clients, the number of BGP routes routes, and the size of the
IGP topology. In essence, sizing considerations are similar to the deployments
of BGP Route Reflector.</t> route reflectors.</t>
    </section>
    <section title="Security Considerations">

<t>This numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>The extension specified in this document provides a new metric value using additional information
for computing routes for BGP route reflectors.  While any improperly used
metric value could impact the resiliency of the network, this extension does
not change the underlying security issues inherent in the existing IBGP per
<xref target="RFC4456" />.</t> format="default"/>.</t>
      <t>This document does not introduce requirements for any new protection
measures. </t>
    </section>
    <section title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <t>This document does not request any has no IANA allocations.</t>

</section>

<section title="Acknowledgments">

<t>Authors would like to thank Keyur Patel, Eric Rosen, Clarence
Filsfils, Uli Bornhauser, Russ White, Jakob Heitz, Mike Shand, Jon
Mitchell, John Scudder, Jeff Haas, Martin Djernaes, Daniele
Ceccarelli, Kieran Milne, Job Snijders, Randy Bush, Alvaro Retana,
Francesca Palombini, Benjamin Kaduk, Zaheduzzaman Sarker, Lars
Eggert, Murray Kucherawy, Tom Petch and Nick Hilliard for their
valuable input.</t>

</section>

<section title="Contributors">

<t>Following persons substantially contributed to the current
format of the document:</t>

<t>
<figure>
<artwork>
Stephane Litkowski
Cisco System

slitkows.ietf@gmail.com
</artwork>
</figure>
</t>

<t>
<figure>
<artwork>
Adam Chappell
GTT Communications, Inc.
Aspira Business Centre
Bucharova 2928/14a
158 00 Prague 13 Stodulky
Czech Republic

adam.chappell@gtt.net
</artwork>
</figure>
</t> actions.</t>
    </section>
  </middle>
  <back>
<references title="Normative References">
      <?rfc include="reference.RFC.2119"?>
	  <?rfc include="reference.RFC.4271"?>
	  <?rfc include="reference.RFC.4456"?>
	  <?rfc include="reference.RFC.8174"?>
      <?rfc include="reference.RFC.7911"?>
    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4271.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4456.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7911.xml"/>
      </references>

<references title="Informative References">
	  <?rfc include="reference.RFC.2328"?>
      <?rfc include="reference.RFC.4364"?>
	  <?rfc include="reference.RFC.5340"?>
	  <?rfc include="reference.RFC.7752"?>
      <?rfc include="reference.RFC.7947"?>
      <references>
        <name>Informative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2328.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.4364.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5340.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7752.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7947.xml"/>

        <reference anchor="ISO10589">
          <front>
            <title>Intermediate system to Intermediate system intra-domain
 routeing information exchange protocol for use in conjunction with
 the protocol for providing the connectionless-mode Network Service (ISO 8473)</title>
            <author>
              <organization abbrev="ISO">International Organization for Standardization</organization>
            </author>
            <date month="Nov" month="November" year="2002"/>
          </front>
		<seriesInfo name="ISO/IEC" value="10589:2002,
          <refcontent>ISO/IEC 10589:2002, Second Edition"/> Edition</refcontent>
        </reference>
      </references>
    </references>
    <section numbered="false" toc="default">
      <name>Acknowledgments</name>
      <t>The authors would like to thank <contact fullname="Keyur Patel"/>, <contact fullname="Eric Rosen"/>, <contact fullname="Clarence Filsfils"/>, <contact fullname="Uli Bornhauser"/>, <contact fullname="Russ White"/>, <contact fullname="Jakob Heitz"/>, <contact fullname="Mike Shand"/>, <contact fullname="Jon
Mitchell"/>, <contact fullname="John Scudder"/>, <contact fullname="Jeff Haas"/>, <contact fullname="Martin Djernæs"/>, <contact fullname="Daniele Ceccarelli"/>, <contact fullname="Kieran Milne"/>, <contact fullname="Job Snijders"/>, <contact fullname="Randy Bush"/>, <contact fullname="Alvaro Retana"/>,
<contact fullname="Francesca Palombini"/>, <contact fullname="Benjamin Kaduk"/>, <contact fullname="Zaheduzzaman Sarker"/>, <contact fullname="Lars Eggert"/>, <contact fullname="Murray Kucherawy"/>, <contact fullname="Tom Petch"/>, and <contact fullname="Nick Hilliard"/> for their
valuable input.</t>
    </section>
    <section numbered="false" toc="default">
      <name>Contributors</name>
      <t>The following persons contributed substantially to the current
format of the document:</t>

      <contact fullname="Stephane Litkowski">
        <organization>Cisco Systems</organization>
        <address>
          <postal>
            <street></street>
            <city></city>
            <region></region>
            <code></code>
            <country></country>
          </postal>
          <email>slitkows.ietf@gmail.com</email>
        </address>
      </contact>

      <contact fullname="Adam Chappell">
        <organization>GTT Communications, Inc.</organization>
        <address>
          <postal>
            <street>Aspira Business Centre</street>
            <street>Bucharova 2928/14a</street>
            <city>158 00 Prague 13 Stodůlky</city>
            <region></region>
            <code></code>
            <country>Czech Republic</country>
          </postal>
          <email>adam.chappell@gtt.net</email>
        </address>
      </contact>
    </section>
  </back>
</rfc>