Internet Engineering Task Force                                 H. Singh
Internet-Draft                                                 W. Beebee
Intended status: Informational                       Cisco Systems, Inc.
Expires: April 29, June 21, 2010                                         C. Donley
                                                                B. Stark
                                                           O. Troan, Ed.
                                                     Cisco Systems, Inc.
                                                        October 26,
                                                       December 18, 2009

           Basic Requirements for IPv6 Customer Edge Routers


   This document specifies requirements for an IPv6 Customer Edge (CE)
   router.  Specifically, the current version of this document focuses
   on the provisioning of an IPv6 CE router and the provisioning of IPv6
   hosts attached to it.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document ( document.  Please review these documents
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   This document specifies requirements for an IPv6 Customer Edge (CE)
   router.  Specifically, the current version of  Code Components extracted from this document focuses
   on the provisioning must
   include Simplified BSD License text as described in Section 4.e of an IPv6 CE router
   the Trust Legal Provisions and are provided without warranty as
   described in the provisioning of IPv6
   hosts attached to it. BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Current IPv4 end-user network architecture . . . . . . . .  4
     3.2.  IPv6 end-user network architecture . . . . . . . . . . . .  5
   4.  Use Cases and Requirements . . . . . . . . . . . . . . . . . .  6
     4.1.  WAN side configuration . . . . . . . . . . . . . . . . . .  6
     4.2.  LAN side configuration . . . . . . . . . . . . . . . . . .  8
     4.3.  General requirements . . . . . . . . . . . . . . . . . . .  9
     4.4.  Security Considerations  . . . . . . . . . . . . . . . . . 10
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Changes in revision 3 . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13

1.  Introduction

   This document defines IPv6 features for a residential or small office
   router referred to as an IPv6 CE router.  Typically these routers
   also support IPv4.

   This document specifies how an IPv6 CE router automatically
   provisions its WAN interface, acquires an address block for
   provisioning of its LAN interfaces and fetches other configuration
   information from the service provider network.  Automatic
   provisioning of more complex topology than a single router with
   multiple LAN interfaces is out of scope for this document.

   See [RFC4779] for a discussion of options available for deploying
   IPv6 in service provider access networks.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Terminology

   End-user Network      one or more links attached to the IPv6 CE
                         router that connect IPv6 hosts.

   IPv6 Customer Edge router  a node intended for home or small office
                         use which forwards IPv6 packets not explicitly
                         addressed to itself.  The IPv6 CE router
                         connects the end-user network to a service
                         provider network.

   IPv6 host             any device implementing an IPv6 stack receiving
                         IPv6 Internet connectivity through the IPv6 CE

   LAN interface         an IPv6 CE router's attachment to a link in the
                         end-user network.  Examples are Ethernets
                         (simple or bridged), 802.11 wireless or other
                         LAN technologies.  An IPv6 CE router may have
                         one or more network layer LAN Interfaces.

   Service Provider      a company that offers its customers access to
                         the Internet.  In this document, a Service
                         Provider specifically offers Internet access
                         using IPv6, and may also offer IPv4 Internet
                         access.  The Service Provider can provide such
                         access over a variety of different transport
                         methods such as DSL, cable, wireless, and

   WAN interface         an IPv6 CE router's attachment to a link used
                         to provide connectivity to the Service Provider
                         network; example link technologies include
                         Ethernets (simple or bridged), PPP links, X.25,
                         Frame Relay, or ATM networks as well as
                         Internet-layer (or higher-layer) "tunnels",
                         such as tunnels over IPv4 or IPv6 itself.

3.  Architecture

3.1.  Current IPv4 end-user network architecture

   An end-user network will likely have to support both IPv4 and IPv6.
   It is not expected that an end-user will change their existing
   network topology with the introduction of IPv6.  There are some
   differences in how IPv6 works and is provisioned which has
   implications for the network architecture.  A typical IPv4 end-user
   network consist of a "plug and play" NAT box connected to the ISP.
   The assumption is a single NAT device with a single link behind it.
   The NAT provides stable addressing allowing for manually configured
   addresses on the nodes in the end-user network.

   A typical IPv4 NAT deployment by default blocks all incoming
   connections.  Opening of ports is typically allowed using UPnP or
   some other firewall control protocol.

   Another consequence of using private address space in the end-user
   network is that it provides stable addressing, i.e. it never changes
   even when you change ISPs, and the addresses are always there even
   when the WAN interface is down or the customer edge router has not
   yet been provisioned.

   Rewriting addresses on the edge of the network also allows for some
   rudimentary multi-homing; even though using NATs for multi-homing
   does not preserve connections during fail-overs [RFC4864].

   Many existing routers support dynamic routing, and advanced end users
   can build arbitrary, complex networks using manual configuration of
   address prefixes combined with a dynamic routing protocol.

3.2.  IPv6 end-user network architecture

   The end-user network architecture for IPv6 should provide equivalent
   or better capabilities and functionality than the equivalent IPv4

   The end-user network is a stub network.  Figure 1 illustrates the
   model topology for the end-user network.

                 An example of a typical end-user network.

                     +-------+-------+                   \
                     |   Service     |                    \
                     |   Provider    |                     | ISP
                     |    Router     |                     | network
                     +-------+-------+                     |
                             |                             /
                             | Customer                   /
                             | Internet connection       /
                      +------+--------+                  \
                      |     IPv6      |                   \
                      | Customer Edge |                    \
                      |    Router     |                    /
                      +---+-------+-+-+                   /
          Network A       |       |   Network B          | Customer
    ---+-------------+----+-    --+--+-------------+---  |network(s)
       |             |               |             |      \
   +----+-----+ +-----+----+     +----+-----+ +-----+----+  \
   |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |  /
   |          | |          |     |          | |          | /
   +----------+ +-----+----+     +----------+ +----------+/

                                 Figure 1

   This architecture describes the:

   o  Basic capabilities of an IPv6 CE router

   o  Provisioning of the WAN interface connecting to the ISP

   o  Provisioning of the LAN interfaces

   The IPv6 CE router defaults to acting as the demarcation point
   between two networks by providing a ULA boundary, a multicast zone
   boundary and ingress and egress traffic filters.

   For IPv6 multicast traffic the IPv6 CE router may act as an MLD proxy
   [RFC4605] and may support a dynamic multicast routing protocol.

   IPv6 CE router may be manually configured in an arbitrary topology
   with a dynamic routing protocol.  Automatic provisioning and
   configuration is described for a single IPv6 CE router only.

4.  Use Cases and Requirements

4.1.  WAN side configuration

   The IPv6 CE router will need to support connectivity to one or more
   access network architectures.  This document describes an IPv6 CE
   router that is not specific to any particular architecture or Service
   Provider, and supports all commonly used architectures.

   IPv6 Neighbor Discovery and DHCP protocols operate over any type of
   IPv6 supported link-layer and there is no need for a link-layer
   specific configuration protocol for IPv6 network layer configuration
   options like what's e.g. as in PPP IPCP for IPv4.  This section makes the assumption
   that the same mechanism will work for any link-layer, be it Ethernet,
   DOCSIS, PPP/PPPoE or others.

   When the router is attached to the WAN interface link it must act as
   an IPv6 host for the purposes of IPv6 interface initialisation, ND
   Router Discovery, Prefix Discovery and stateless or stateful interface
   address assignment
   ([RFC4861]/[RFC4862]). ([RFC4862]/[RFC3315]).  The router acts as a
   requesting router for the purposes of DHCP prefix delegation

   DHCP address assignment (IA_NA) and DHCP prefix delegation (IA_PD)
   should be done as a single DHCP session.

   Link-layer requirements:

   WLL-1:  The IPv6 CE router MUST support IPv6 over Ethernet [RFC2464].

   WLL-2:  The IPv6 CE router MUST support IPv6 over PPP [RFC5072].  It
           MUST support use of IPv6 [RFC5072] and
           PPPoE [RFC2516].  In a dual-stack environment with IPCP and
           IPV6CP running over one PPP within PPPoE. logical channel, the NCPs MUST be
           treated as independent of each other and start and terminate

   Address assignment requirements:

   WAA-1:  The IPv6 CE router MUST support SLAAC ([RFC4862]). [RFC4862].

   WAA-2:  The IPv6 CE router MUST follow the recommendation in
           [I-D.ietf-6man-ipv6-subnet-model] and in particular the
           handling of the L-bit in the Router Advertisement Prefix
           Information Option.

   WAA-3:  The IPv6 CE router MUST support DHCP [RFC3315] client
           behavior.  It MUST be able to support the following DHCP
           options: IA_NA, Reconfigure Accept([RFC3315]), Accept [RFC3315], DNS_SERVERS

   WAA-4:  Th  The IPv6 CE router SHOULD support the DHCP SNTP option
           [RFC4075] and the Information Refresh Time Option
           ([RFC4242]. [RFC4242].

   WAA-5:  If the IPv6 CE router receives an RA message (described in
           [RFC4861]) with the M-bit set to 1, the IPv6 CE router MUST
           do DHCP address assignment (request an IA_NA. IA_NA option).  If the
           IPv6 CE router is unable to assign an address through SLAAC
           it MAY request do DHCP address assignment (request an IA_NA IA_NA) even if
           the M-bit is set to 0.

   WAA-6:  If the IPv6 CE router does not acquire a global IPv6 address
           from either SLAAC or DHCP, then it MUST create a global IPv6
           address from its delegated prefix and configure that on one
           of its internal virtual network interfaces.  As a router the
           IPv6 CE router follows the weak host model [RFC1122] and when
           originating packets out the WAN-interface will use a suitably
           scoped source address from one of its other interfaces.

   Prefix Delegation requirements:

   WPD-1:  The IPv6 CE router MUST support DHCP prefix delegation
           requesting router behaviour behavior as specified in [RFC3633] (IA_PD
           option).  The IPv6 CE router MUST ask for a prefix large
           enough to cover all of its LAN interfaces.

   WPD-2:  The IPv6 CE router MUST always initiate DHCP prefix
           delegation, regardless of the M and O-bits in a received
           Router Advertisement.  If the IPv6 CE Router initiates DHCP
           before receiving a Router Advertisement it MUST also request
           an IA_NA. IA_NA option in DHCP.

   WPD-3:  Absent of other routing information the IPv6 CE router MUST
           use Router Discovery as specified in [RFC4861] to discover a
           default router and install a default route in its routing
           table with the discovered router's address as the next-hop.

   WPD-4:  If the delegated prefix is an aggregate route of multiple,
           more-specific routes the IPv6 CE router MUST discard packets
           that match the aggregate route, but not any of the more-
           specific routes.  In other words, the "next-hop" for the
           aggregate route should be the null destination.  This is
           necessary to prevent forwarding loops when some addresses
           covered by the aggregate are not reachable.  [RFC4632]

   WPD-4: reachable [RFC4632].  The
           IPv6 CE Router SHOULD send an ICMPv6 Destination Unreachable
           according to section 3.1 [RFC4443] back to the source of the
           packet if the packet is to be dropped due to this rule.

   WPD-5:  If the IPv6 CE router requests both an IA_NA and an IA_PD in
           DHCP, it MUST accept an IA_PD in DHCP Advertise/Reply
           messages, even if the message does not contain any addresses
           (IA_NA options with status code NoAddrsAvail).


   WPD-6:  An IPv6 CE router MUST not by default initiate any dynamic
           routing protocol on its WAN interface.

4.2.  LAN side configuration

   The IPv6 CE router distributes configuration information obtained
   during WAN interface provisioning to IPv6 hosts and assists IPv6
   hosts in obtaining IPv6 addresses.  It also supports connectivity of
   these devices in the absence of any working WAN interface.

   An IPv6 CE router will be expected to support an IPv6 end-user
   network and IPv6 hosts that exhibit the following characteristics:

   1.  Link-local addresses are insufficient for allowing IPv6
       applications to communicate with each other in the end-user
       network.  The IPv6 CE router will need to enable this
       communication by providing globally-scoped unicast addresses or
       ULAs [RFC4193] whether or not WAN connectivity exists.

   2.  IPv6 hosts will be capable of using SLAAC and may be capable of
       using DHCP for acquiring their addresses.

   3.  IPv6 hosts will use DHCP for other configuration information,
       such as the DNS_SERVERS option for acquiring DNS information.

   Unless otherwise specified these requirements only apply to the IPv6
   CE router's LAN interfaces.


   L-1:   The IPv6 CE router MUST support ULA addressing ([RFC4193]). [RFC4193].

   L-2:   The IPv6 CE router MUST have a ULA prefix that it maintains
          consistently across reboots.  The value of the ULA prefix
          SHOULD be user configurable.

   L-3:   The IPv6 CE router by default MUST act as a site border router
          according to section 4.3 of RFC4193 [RFC4193] and filter packets with
          Local IPv6 source or destination addresses accordingly.

   L-4:   The IPv6 CE router MUST support router behavior of Neighbor
          Discovery for IPv6 ([RFC4861]). [RFC4861].

   L-5:   The IPv6 CE router must MUST assign a separate /64 from its
          delegated prefix (and ULA prefix if configured to provide ULA
          addressing) for each of its LAN interfaces.  The IPV6 CE
          router MUST make the interface an advertising interface
          according to
         RFC4861. [RFC4861].  In router advertisements messages,
          the Prefix Information Option's A/L-bits MUST be set to 1 by
          default; the A/L bits setting SHOULD be user configurable.

   L-6:   The IPv6 CE router MUST support a DHCP server ([RFC3315]) [RFC3315] on its
          LAN interfaces.  It MAY support Stateless Dynamic Host
          Configuration Protocol (DHCP) Service for IPv6 [RFC3736].

   L-7:   The IPv6 CE SHOULD support DHCP address assignment

   L-7: (IA_NA)

   L-8:   Unless the IPv6 CE router is configured to support the DHCP IA_NA,
          IA_NA option, it SHOULD set M=0 and O=1 in its RA messages.

   L-8: Router
          Advertisement messages [RFC4861].

   L-9:   The IPv6 CE router MUST support providing DNS information in
          the DHCP DNS_SERVERS option ([RFC3646]).

   L-9: [RFC3646].

   L-10:  The IPv6 CE router SHOULD pass the additional set of DHCP
          options received from the DHCP client on its WAN interface
          from the Service Provider to IPv6 hosts.

4.3.  General requirements

   The IPv6 CE router is responsible for implementing IPv6 routing; that
   is, the IPv6 CE router must look up the IPv6 Destination address in
   its routing table to decide to which interface it should send the

   In this role, the IPv6 CE router is responsible for ensuring that
   traffic using its ULA addressing does not go out the WAN interface,
   and does not originate from the WAN interface.



   An IPv6 CE router is an IPv6 node and MUST follow according to the IPv6 Node
   Requirements [RFC4294] specification.

   G-2:  The IPV6 CE router SHOULD support the following RFCs:

         *  Internet Protocol, Version 6 (IPv6) Specification [RFC2460]

         *  Stateless Dynamic Host Configuration Protocol (DHCP) Service
            for IPv6 [RFC3736]

         *  Default Router Preferences and More-Specific Routes

         *  IP Version 6 Addressing Architecture [RFC4291]

         *  IPv6 Subnet Model: the Relationship between Links and Subnet
            Prefixes [I-D.ietf-6man-ipv6-subnet-model]


   The IPv6 CE router MUST NOT forward any IPv6 traffic between its LAN
   Interface(s) and its WAN Interface until the router has successfully
   completed the IPv6 address acquisition process.

4.4.  Security Considerations

   It is considered a best practice to filter obviously malicious
   traffic (e.g. spoofed packets, "martian" addresses, etc.).  Thus, the
   IPv6 CE router should support basic stateless egress and ingress
   filters.  The CE router should also offer mechanisms to filter
   traffic entering the customer network; however, the method by which
   vendors implement configurable packet filtering is beyond the scope
   of this document.

   Security requirements:

   S-1:  The IPv6 CE router SHOULD support

   S-2:  The IPv6 CE router MUST support ingress filtering in accordance
         with [RFC2827](BCP 38)

5.  Acknowledgements

   Thanks to the following people (in alphabetical order) for their
   guidance and feedback:

   Mikael Abrahamsson, Merete Asak, Scott Beuker, Rex Bullinger, Brian
   Carpenter, Remi Denis-Courmont, Alain Durand, Katsunori Fukuoka, Tony
   Hain, Thomas Herbst, Kevin Johns, Stephen Kramer, Victor Kuarsingh,
   Francois-Xavier Le Bail, David Miles, Shin Miyakawa, Jean-Francois
   Mule, Michael Newbery, Carlos Pignataro, John Pomeroy, Antonio
   Querubin, Teemu Savolainen, Matt Schmitt, Hiroki Sato, Mark Townsley,
   Bernie Volz, James Woodyatt, Dan Wing and Cor Zwart

   This draft is based in part on CableLabs' eRouter specification.  The
   authors wish to acknowledge the additional contributors from the
   eRouter team:

   Ben Bekele, Amol Bhagwat, Ralph Brown, Eduardo Cardona, Margo Dolas,
   Toerless Eckert, Doc Evans, Roger Fish, Michelle Kuska, Diego
   Mazzola, John McQueen, Harsh Parandekar, Michael Patrick, Saifur
   Rahman, Lakshmi Raman, Ryan Ross, Ron da Silva, Madhu Sudan, Dan
   Torbet and Greg White

6.  Contributors

   The following people have participated as co-authors or provided
   substantial contributions to this document: Ralph Droms, Kirk
   Erichsen, Fred Baker, Jason Weil, Lee Howard, Jean-Francois Tremblay,
   Yiu Lee, John Jason Brzozowski and Heather Kirksey.

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Normative References

              Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
              Model: the Relationship between Links and Subnet
              Prefixes", draft-ietf-6man-ipv6-subnet-model-05 draft-ietf-6man-ipv6-subnet-model-06 (work in
              progress), May November 2009.

              Woodyatt, J., "Recommended Simple Security Capabilities in
              Customer Premises Equipment for Providing Residential IPv6
              Internet Service", draft-ietf-v6ops-cpe-simple-security-08
              (work in progress), October 2009.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, December 1998.

   [RFC2516]  Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,
              and R. Wheeler, "A Method for Transmitting PPP Over
              Ethernet (PPPoE)", RFC 2516, February 1999.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC3646]  Droms, R., "DNS Configuration options for Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              December 2003.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.

   [RFC4075]  Kalusivalingam, V., "Simple Network Time Protocol (SNTP)
              Configuration Option for DHCPv6", RFC 4075, May 2005.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, November 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4242]  Venaas, S., Chown, T., and B. Volz, "Information Refresh
              Time Option for Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 4242, November 2005.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4294]  Loughney, J., "IPv6 Node Requirements", RFC 4294,
              April 2006.

   [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.

   [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
              "Internet Group Management Protocol (IGMP) / Multicast
              Listener Discovery (MLD)-Based Multicast Forwarding
              ("IGMP/MLD Proxying")", RFC 4605, August 2006.

   [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
              (CIDR): The Internet Address Assignment and Aggregation
              Plan", BCP 122, RFC 4632, August 2006.

   [RFC4779]  Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and
              J. Palet, "ISP IPv6 Deployment Scenarios in Broadband
              Access Networks", RFC 4779, January 2007.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC4864]  Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
              E. Klein, "Local Network Protection for IPv6", RFC 4864,
              May 2007.

   [RFC5072]  S.Varada, Haskins, D., and E. Allen, "IP Version 6 over
              PPP", RFC 5072, September 2007.

Appendix A.  Changes in revision 3

   o  Added "the CPE Router SHOULD send an ICMPv6 Destination
      Unreachable ([RFC4443] section 3.1) back to the source of the
      packet if the packet is to be dropped due to aggregate null

   o  Clarified that if IPV6CP and IPCP run over the same PPP session
      they should be treated independently.

   o  Removed RFC2460 in the section of RFCs that SHOULD be supported.

   o  Clarified that the router acts as a host for the purposes of
      address assignment.  Not for any other ND function e.g Redirects.

   o  Improved default router selection / default route RIB insertion

   o  Added text describing that the weak host model has to be supported
      in the unnumbered WAN case.

Authors' Addresses

   Hemant Singh
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719

   Phone: +1 978 936 1622
   Wes Beebee
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA  01719

   Phone: +1 978 936 2030

   Chris Donley
   858 Coal Creek Circle
   Louisville, CO  80027


   Barbara Stark
   725 W Peachtree St
   Atlanta, GA  30308


   Ole Troan (editor)
   Cisco Systems, Inc.
   Veversmauet 8
   N-5017 BERGEN,   5017