draft-ietf-l2vpn-arp-mediation-11.txt   draft-ietf-l2vpn-arp-mediation-12.txt 
L2VPN Working Group Himanshu Shah Force10 Networks L2VPN Working Group Himanshu Shah Force10 Networks
Intended Status: Proposed Standard Eric Rosen Cisco System Intended Status: Proposed Standard Eric Rosen Cisco System
Internet Draft Giles Heron British Telecom Internet Draft Giles Heron British Telecom
Vach Kompella Alcatel-Lucent Vach Kompella Alcatel-Lucent
Expires: December 2009 Expires: December 2009
ARP Mediation for IP Interworking of Layer 2 VPN ARP Mediation for IP Interworking of Layer 2 VPN
draft-ietf-l2vpn-arp-mediation-11.txt draft-ietf-l2vpn-arp-mediation-12.txt
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance This Internet-Draft is submitted to IETF in full conformance
with the provisions of BCP 78 and BCP 79. This document may with the provisions of BCP 78 and BCP 79. This document may
contain material from IETF Documents or IETF Contributions contain material from IETF Documents or IETF Contributions
published or made publicly available before November 10, 2008. published or made publicly available before November 10, 2008.
The person(s) controlling the copyright in some of this material The person(s) controlling the copyright in some of this material
may not have granted the IETF Trust the right to allow may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards modifications of such material outside the IETF Standards
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months and may be updated, replaced, or obsoleted by other months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet- documents at any time. It is inappropriate to use Internet-
Drafts as reference material or to cite them other than as "work Drafts as reference material or to cite them other than as "work
in progress." in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html http://www.ietf.org/shadow.html
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
This Internet-Draft will expire on December 2009. This Internet-Draft will expire on December 2009.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents in effect on the date of
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a routing protocol between them, as long as the routing protocol a routing protocol between them, as long as the routing protocol
runs over IP. runs over IP.
Conventions used in this document Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described "OPTIONAL" in this document are to be interpreted as described
in [RFC 2119]. in [RFC 2119].
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Table of Contents Table of Contents
Copyright Notice........................................... 2 Copyright Notice........................................... 2
1. Contributing Authors....................................... 4 1. Contributing Authors....................................... 4
2. Introduction............................................... 4 2. Introduction............................................... 4
3. ARP Mediation (AM) function................................ 5 3. ARP Mediation (AM) function................................ 5
4. IP Layer 2 Interworking Circuit............................ 7 4. IP Layer 2 Interworking Circuit............................ 7
5. IP Address Discovery Mechanisms............................ 7 5. IP Address Discovery Mechanisms............................ 7
5.1. Discovery of IP Addresses of Locally Attached IPv4 CE. 8 5.1. Discovery of IP Addresses of Locally Attached IPv4 CE. 8
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9.2. RIP.................................................. 24 9.2. RIP.................................................. 24
9.3. IS-IS................................................ 24 9.3. IS-IS................................................ 24
10. Multi-domain considerations.............................. 25 10. Multi-domain considerations.............................. 25
11. Security Considerations.................................. 26 11. Security Considerations.................................. 26
11.1. Control plane security.............................. 26 11.1. Control plane security.............................. 26
11.2. Data plane security................................. 27 11.2. Data plane security................................. 27
12. Acknowledgements......................................... 27 12. Acknowledgements......................................... 27
13. References............................................... 28 13. References............................................... 28
13.1. Normative References................................ 28 13.1. Normative References................................ 28
13.2. Informative References.............................. 29 13.2. Informative References.............................. 29
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14. Authors' Addresses....................................... 29 14. Authors' Addresses....................................... 29
1. Contributing Authors 1. Contributing Authors
This document is the combined effort of the following This document is the combined effort of the following
individuals and many others who have carefully reviewed the individuals and many others who have carefully reviewed the
document and provided the technical clarifications. document and provided the technical clarifications.
W. Augustyn consultant W. Augustyn consultant
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In a typical implementation, illustrated in the diagram below, In a typical implementation, illustrated in the diagram below,
the CE devices are connected to the Provider Edge (PE) devices the CE devices are connected to the Provider Edge (PE) devices
via Attachment Circuits (AC). The ACs are Layer 2 links. In a via Attachment Circuits (AC). The ACs are Layer 2 links. In a
pure L2VPN, if traffic sent from CE1 via AC1 reaches CE2 via pure L2VPN, if traffic sent from CE1 via AC1 reaches CE2 via
AC2, both ACs would have to be of the same type (i.e., both AC2, both ACs would have to be of the same type (i.e., both
Ethernet, both FR, etc.). However, if it is known that only IP Ethernet, both FR, etc.). However, if it is known that only IP
traffic will be carried, the ACs can be of different traffic will be carried, the ACs can be of different
technologies, provided that the PEs provide the appropriate technologies, provided that the PEs provide the appropriate
procedures to allow the proper transfer of IP packets. procedures to allow the proper transfer of IP packets.
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+-----+ +-----+
+------ -----| CE3 | +------ -----| CE3 |
| +-----+ | +-----+
+-----+ +-----+
......| PE3 |........... ......| PE3 |...........
. +-----+ . . +-----+ .
. | . . | .
. | . . | .
+-----+ AC1 +-----+ Service +-----+ AC2 +-----+ +-----+ AC1 +-----+ Service +-----+ AC2 +-----+
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used to resolve IP address to Link Layer address association used to resolve IP address to Link Layer address association
purposes. For instance in IPv4, ARP and InvArp protocols are purposes. For instance in IPv4, ARP and InvArp protocols are
used for address resolution while in IPv6 Neighbor Discovery and used for address resolution while in IPv6 Neighbor Discovery and
Inverse Neighbor Discovery protocol based on ICMPv6 is used for Inverse Neighbor Discovery protocol based on ICMPv6 is used for
address resolution. address resolution.
3. ARP Mediation (AM) function 3. ARP Mediation (AM) function
The ARP Mediation (AM) function is an element of a PE node that The ARP Mediation (AM) function is an element of a PE node that
deals with the IP address resolution for CE devices connected deals with the IP address resolution for CE devices connected
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via an VPWS L2VPN. By placing this function in the PE node, ARP via an VPWS L2VPN. By placing this function in the PE node, ARP
Mediation is transparent to the CE devices. Mediation is transparent to the CE devices.
For a given point-to-point connection between a pair of CEs, the For a given point-to-point connection between a pair of CEs, the
ARP Mediation procedure depends on whether the packets being ARP Mediation procedure depends on whether the packets being
forwarded are IPv4 or IPV6. A PE that is to perform ARP forwarded are IPv4 or IPV6. A PE that is to perform ARP
Mediation for IPv4 packets must perform the following logical Mediation for IPv4 packets must perform the following logical
steps: steps:
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forwarding the packets across the VPWS to the remote PE. forwarding the packets across the VPWS to the remote PE.
3. Intercept Neighbor Discovery and Inverse Neighbor Discovery 3. Intercept Neighbor Discovery and Inverse Neighbor Discovery
packets received over the VPWS from the remote PE, possibly packets received over the VPWS from the remote PE, possibly
modifying them (if required for the type of outgoing AC) modifying them (if required for the type of outgoing AC)
before forwarding to the local CE, and also learning before forwarding to the local CE, and also learning
information about the IPv6 configuration of the remote CE. information about the IPv6 configuration of the remote CE.
PEs MUST support ARP mediation for IPv4 L2 Interworking PEs MUST support ARP mediation for IPv4 L2 Interworking
circuits. Support for IPv6 L2 interworking circuits is OPTIONAL. circuits. Support for IPv6 L2 interworking circuits is OPTIONAL.
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Details for the above-described procedures are given in the Details for the above-described procedures are given in the
following sections. following sections.
4. IP Layer 2 Interworking Circuit 4. IP Layer 2 Interworking Circuit
The IP Layer 2 interworking Circuit refers to interconnection of The IP Layer 2 interworking Circuit refers to interconnection of
the Attachment Circuit with the IP Layer 2 Transport pseudowire the Attachment Circuit with the IP Layer 2 Transport pseudowire
that carries IP datagrams as the payload. The ingress PE removes that carries IP datagrams as the payload. The ingress PE removes
the data link header of its local Attachment Circuit and the data link header of its local Attachment Circuit and
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- Establishment of the PW - Establishment of the PW
The establishment of the PW occurs independently from local CE The establishment of the PW occurs independently from local CE
IP address discovery. During the period when the PW has been IP address discovery. During the period when the PW has been
established but the local CE IP device has not been discovered, established but the local CE IP device has not been discovered,
only broadcast/multicast IP frames are propagated between the only broadcast/multicast IP frames are propagated between the
Attachment Circuit and pseudowire; unicast IP datagrams are Attachment Circuit and pseudowire; unicast IP datagrams are
dropped. The IP destination address is used to classify dropped. The IP destination address is used to classify
unicast/multicast packets. unicast/multicast packets.
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The unicast IP frames are propagated between AC and pseudowire The unicast IP frames are propagated between AC and pseudowire
only when CE IP devices on both Attachment Circuits have been only when CE IP devices on both Attachment Circuits have been
discovered, notified and proxy functions have completed. discovered, notified and proxy functions have completed.
The need to wait for address resolution completion before the The need to wait for address resolution completion before the
unicast IP traffic can flow is simple. unicast IP traffic can flow is simple.
. PEs do not perform routing operations . PEs do not perform routing operations
. Destination IP address in the packet is not necessarily . Destination IP address in the packet is not necessarily
that of the attached CE that of the attached CE
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Attachment Circuit. However, customer facing access topologies Attachment Circuit. However, customer facing access topologies
may exist whereby more than one CE appears to be connected to may exist whereby more than one CE appears to be connected to
the PE on a single Attachment Circuit. For example, this could the PE on a single Attachment Circuit. For example, this could
be the case when CEs are connected to a shared LAN that connects be the case when CEs are connected to a shared LAN that connects
to the PE. In such case, the PE MUST select one local CE. The to the PE. In such case, the PE MUST select one local CE. The
selection could be based on manual configuration or the PE may selection could be based on manual configuration or the PE may
optionally use following selection criteria. In either case, optionally use following selection criteria. In either case,
manual configuration of IP address of the local CE (and its MAC manual configuration of IP address of the local CE (and its MAC
address) MUST be supported. address) MUST be supported.
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o Wait to learn the IP address of the remote CE (through PW o Wait to learn the IP address of the remote CE (through PW
signaling) and then select the local CE that is sending signaling) and then select the local CE that is sending
the request for IP address of the remote CE. the request for IP address of the remote CE.
o Augment cross checking with the local IP address learned o Augment cross checking with the local IP address learned
through listening of link local multicast packets (as per through listening of link local multicast packets (as per
section 5.1.1 above) section 5.1.1 above)
o Augment cross checking with the local IP address learned o Augment cross checking with the local IP address learned
through the Router Discovery protocol (as described below through the Router Discovery protocol (as described below
in section 5.1.5). in section 5.1.5).
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address of the CE as a means of verifying the continued address of the CE as a means of verifying the continued
existence of the address and its MAC address binding. The existence of the address and its MAC address binding. The
absence of a response from the CE device for a given number of absence of a response from the CE device for a given number of
retries could be used as a trigger for withdrawal of the IP retries could be used as a trigger for withdrawal of the IP
address advertisement to the remote PE. The local PE would then address advertisement to the remote PE. The local PE would then
re-enter the address resolution phase to rediscover the IP re-enter the address resolution phase to rediscover the IP
address of the attached CE. Note that this "heartbeat" scheme is address of the attached CE. Note that this "heartbeat" scheme is
needed only for broadcast links (such as Ethernet AC), where the needed only for broadcast links (such as Ethernet AC), where the
failure of a CE device may otherwise be undetectable. failure of a CE device may otherwise be undetectable.
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5.1.3. CE Devices Using Inverse ARP 5.1.3. CE Devices Using Inverse ARP
If a CE device uses Inverse ARP to determine the IP address of If a CE device uses Inverse ARP to determine the IP address of
its neighbor, the attached PE processes the Inverse ARP request its neighbor, the attached PE processes the Inverse ARP request
from the Attachment Circuit and responds with an Inverse ARP from the Attachment Circuit and responds with an Inverse ARP
reply containing the IP address of the remote CE, if the address reply containing the IP address of the remote CE, if the address
is known. If the PE does not yet have the IP address of the is known. If the PE does not yet have the IP address of the
remote CE, it does not respond, but records the IP address of remote CE, it does not respond, but records the IP address of
the local CE and the circuit information. Subsequently, when the the local CE and the circuit information. Subsequently, when the
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o The PE learns the IP address of the local CE from the o The PE learns the IP address of the local CE from the
Configure-Request received with the IP-Address option Configure-Request received with the IP-Address option
(0x03). If the IP address is non-zero, PE records the (0x03). If the IP address is non-zero, PE records the
address and responds with Configure-Ack. However, if the address and responds with Configure-Ack. However, if the
IP address is zero, PE responds with Configure-Reject (as IP address is zero, PE responds with Configure-Reject (as
this is a request from CE to assign it an IP address). this is a request from CE to assign it an IP address).
Also, the IP address option is set with zero value in the Also, the IP address option is set with zero value in the
Configure-Reject response to instruct the CE to not Configure-Reject response to instruct the CE to not
include that option in subsequent new Configure-Request. include that option in subsequent new Configure-Request.
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o If the PE receives Configure-Request without the IP- o If the PE receives Configure-Request without the IP-
Address option, it responds with a Configure-Ack. In this Address option, it responds with a Configure-Ack. In this
case the PE is unable to learn the IP address of the local case the PE is unable to learn the IP address of the local
CE using IPCP and hence must rely on other means as CE using IPCP and hence must rely on other means as
described in sections 5.1.1 and 5.1.5. Note that in order described in sections 5.1.1 and 5.1.5. Note that in order
to employ other learning mechanisms, the IPCP negotiations to employ other learning mechanisms, the IPCP negotiations
must have reached the open state. must have reached the open state.
o If the PE does not know the IP address of the remote CE, o If the PE does not know the IP address of the remote CE,
it sends a Configure-Request without the IP-Address it sends a Configure-Request without the IP-Address
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5.1.6. Manual Configuration 5.1.6. Manual Configuration
In some cases, it may not be possible to discover the IP address In some cases, it may not be possible to discover the IP address
of the local CE device using the mechanisms described in section of the local CE device using the mechanisms described in section
5.1 above. In such cases manual configuration MAY be used. All 5.1 above. In such cases manual configuration MAY be used. All
implementations of this draft MUST support manual configuration implementations of this draft MUST support manual configuration
of the IPv4 address of the local CE. This is the only REQUIRED of the IPv4 address of the local CE. This is the only REQUIRED
mode for a PE to support. mode for a PE to support.
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5.2. How a CE Learns the IPv4 address of a remote CE 5.2. How a CE Learns the IPv4 address of a remote CE
Once the local PE has received the IP address information of the Once the local PE has received the IP address information of the
remote CE from the remote PE, it will either initiate an address remote CE from the remote PE, it will either initiate an address
resolution request or respond to an outstanding request from the resolution request or respond to an outstanding request from the
attached CE device. attached CE device.
5.2.1. CE Devices Using ARP 5.2.1. CE Devices Using ARP
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Inverse ARP has not been enabled. In either case the CE has used Inverse ARP has not been enabled. In either case the CE has used
other means to learn the IP address of his neighbor. other means to learn the IP address of his neighbor.
5.2.3. CE Devices Using PPP 5.2.3. CE Devices Using PPP
When the PE learns the IP address of the remote CE, it should When the PE learns the IP address of the remote CE, it should
initiate a Configure-Request and set the IP-Address option to initiate a Configure-Request and set the IP-Address option to
the IP address of the remote CE to notify the IP address of the the IP address of the remote CE to notify the IP address of the
remote CE to the local CE. remote CE to the local CE.
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5.3. Discovery of IP Addresses of IPv6 CE Devices 5.3. Discovery of IP Addresses of IPv6 CE Devices
5.3.1. Distinguishing factors between IPv4 and IPv6 5.3.1. Distinguishing factors between IPv4 and IPv6
The IPv6 uses ICMPv6 extensions to resolve IP address and link The IPv6 uses ICMPv6 extensions to resolve IP address and link
address associations. These are essentially IP packets as address associations. These are essentially IP packets as
compared to ARP and invARP in IPv4 which is a separate protocol compared to ARP and invARP in IPv4 which is a separate protocol
and not IP packets. The IP pseudowire can not be used to carry and not IP packets. The IP pseudowire can not be used to carry
the ARP/invARP packets and hence requires local processing of the ARP/invARP packets and hence requires local processing of
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The PE MUST also be capable of generating packets in order to The PE MUST also be capable of generating packets in order to
interwork between Neighbor Discovery (ND) and Inverse Neighbor interwork between Neighbor Discovery (ND) and Inverse Neighbor
Discovery (IND). This is specified in Sections 5.3.3. to Section Discovery (IND). This is specified in Sections 5.3.3. to Section
5.3.6. below. 5.3.6. below.
A PE device MUST also be capable of intercepting Router A PE device MUST also be capable of intercepting Router
Discovery packets. This is required in order to translate Discovery packets. This is required in order to translate
between different link layer addresses. If a Router Discovery between different link layer addresses. If a Router Discovery
message contains a link layer address, then the PE MAY also use message contains a link layer address, then the PE MAY also use
this message to discover the link layer address and IPv6 this message to discover the link layer address and IPv6
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interface address. This is described in more detail in Section interface address. This is described in more detail in Section
5.3.7. and Section 5.3.8. 5.3.7. and Section 5.3.8.
The PE device MUST learn a list of CE IPv6 interface addresses The PE device MUST learn a list of CE IPv6 interface addresses
for its directly-attached CE and another list of CE IPv6 for its directly-attached CE and another list of CE IPv6
interface addresses for the far-end CE. The PE device MUST also interface addresses for the far-end CE. The PE device MUST also
learn the link-layer address of the local CE and be able to use learn the link-layer address of the local CE and be able to use
it when forwarding traffic between the local and far-end CEs. it when forwarding traffic between the local and far-end CEs.
The PE MAY also wish to monitor the source link-layer address of The PE MAY also wish to monitor the source link-layer address of
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1. Forward the Neighbor Solicitation to the local CE after 1. Forward the Neighbor Solicitation to the local CE after
replacing the source link-layer address with the link-layer replacing the source link-layer address with the link-layer
address of the local AC. address of the local AC.
2. Send an Inverse Neighbor Solicitation to the local CE, 2. Send an Inverse Neighbor Solicitation to the local CE,
specifying the far-end CE's IP address and the link-layer specifying the far-end CE's IP address and the link-layer
address of the local AC. address of the local AC.
5.3.4. Processing of Neighbor Advertisements 5.3.4. Processing of Neighbor Advertisements
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A Neighbor Advertisement received on an AC from a local CE A Neighbor Advertisement received on an AC from a local CE
SHOULD be inspected to determine and learn an IPv6 interface SHOULD be inspected to determine and learn an IPv6 interface
address and any link-layer address provided. The packet MUST address and any link-layer address provided. The packet MUST
then be forwarded over the pseudowire unmodified. then be forwarded over the pseudowire unmodified.
A Neighbor Advertisement received over the pseudowire SHOULD be A Neighbor Advertisement received over the pseudowire SHOULD be
inspected to determine and learn an IPv6 interface address for inspected to determine and learn an IPv6 interface address for
the far-end CE. If a source link-layer address option is the far-end CE. If a source link-layer address option is
present, the PE MUST remove it. The PE MAY substitute an present, the PE MUST remove it. The PE MAY substitute an
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these SHOULD also be learned. The packet MUST then be forwarded these SHOULD also be learned. The packet MUST then be forwarded
over the pseudowire unmodified. over the pseudowire unmodified.
An Inverse Neighbor Solicitation received over the pseudowire An Inverse Neighbor Solicitation received over the pseudowire
SHOULD be inspected to determine and learn one or more interface SHOULD be inspected to determine and learn one or more interface
addresses for the far-end CE. If the local AC supports Inverse addresses for the far-end CE. If the local AC supports Inverse
Neighbor Discovery (e.g., a Frame Relay AC), the packet may be Neighbor Discovery (e.g., a Frame Relay AC), the packet may be
forwarded to the local CE, after modifying the link-layer forwarded to the local CE, after modifying the link-layer
address options to match the type of the local AC. address options to match the type of the local AC.
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If the local AC does not support Inverse Neighbor Discovery If the local AC does not support Inverse Neighbor Discovery
(IND), processing of the packet depends on whether the PE has (IND), processing of the packet depends on whether the PE has
learned at least one interface address for its directly-attached learned at least one interface address for its directly-attached
CE. If it has learned at least one interface address for the CE, CE. If it has learned at least one interface address for the CE,
the PE MUST discard the Inverse Neighbor Solicitation (INS) and the PE MUST discard the Inverse Neighbor Solicitation (INS) and
generate an Inverse Neighbor Advertisement (INA) back into the generate an Inverse Neighbor Advertisement (INA) back into the
pseudowire. The destination address of the INA is the source pseudowire. The destination address of the INA is the source
address from the INS, the source address is one of the local address from the INS, the source address is one of the local
CE's interface addresses, and all the local CE's interface CE's interface addresses, and all the local CE's interface
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after modifying the link-layer address options to match the type after modifying the link-layer address options to match the type
of the local AC. of the local AC.
If the local AC does not support Inverse Neighbor Discovery, the If the local AC does not support Inverse Neighbor Discovery, the
PE MUST discard the INA and generate a Neighbor Advertisement PE MUST discard the INA and generate a Neighbor Advertisement
(NA) towards its local CE. The source address of the NA is the (NA) towards its local CE. The source address of the NA is the
source address from the INA, the destination address is the source address from the INA, the destination address is the
destination address from the INA and the link-layer address is destination address from the INA and the link-layer address is
that of the local AC on the PE. that of the local AC on the PE.
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5.3.7. Processing of Router Solicitations 5.3.7. Processing of Router Solicitations
A Router Solicitation received on an AC from a local CE SHOULD A Router Solicitation received on an AC from a local CE SHOULD
be inspected to determine and learn an interface address for the be inspected to determine and learn an interface address for the
CE, and, if present, the link-layer address of the CE. It MUST CE, and, if present, the link-layer address of the CE. It MUST
then be forwarded unmodified over the pseudowire. then be forwarded unmodified over the pseudowire.
A Router Solicitation received over the pseudowire SHOULD be A Router Solicitation received over the pseudowire SHOULD be
inspected to determine and learn an interface address for the inspected to determine and learn an interface address for the
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5.3.9. Duplicate Address Detection [RFC 2462] 5.3.9. Duplicate Address Detection [RFC 2462]
Duplicate Address Detection allows IPv6 hosts and routers to Duplicate Address Detection allows IPv6 hosts and routers to
ensure that the addresses assigned to interfaces are unique ensure that the addresses assigned to interfaces are unique
on a link. As with all Neighbor Discovery packets, those on a link. As with all Neighbor Discovery packets, those
used in Duplicate Address Detection will simply flow used in Duplicate Address Detection will simply flow
through the pseudowire, being inspected at the PEs at each through the pseudowire, being inspected at the PEs at each
end. Processing is performed as above. However, the source end. Processing is performed as above. However, the source
address of Neighbor Solicitations used in Duplicate Address address of Neighbor Solicitations used in Duplicate Address
Detection is the unspecified address, so the PEs can not Detection is the unspecified address, so the PEs can not
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
learn the CE's interface address (nor would it make sense learn the CE's interface address (nor would it make sense
to do so, given that at least one address is tentative at to do so, given that at least one address is tentative at
that time). that time).
6. CE IPv4 Address Signaling between PEs 6. CE IPv4 Address Signaling between PEs
6.1. When to Signal an IPv4 address of a CE 6.1. When to Signal an IPv4 address of a CE
A PE device advertises the IPv4 address of the attached CE only A PE device advertises the IPv4 address of the attached CE only
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the same manner as described above. However, since the CE the same manner as described above. However, since the CE
devices are local, the distribution of IPv4 addresses for these devices are local, the distribution of IPv4 addresses for these
CE devices is a local step. CE devices is a local step.
Note that the PEs discover the IPv6 addresses of the remote CE Note that the PEs discover the IPv6 addresses of the remote CE
by intercepting Neighbor Discovery and Inverse Neighbor by intercepting Neighbor Discovery and Inverse Neighbor
Discovery packets that have been passed in-band through the Discovery packets that have been passed in-band through the
pseudowire. Hence, there is no need to communicate the IPv6 pseudowire. Hence, there is no need to communicate the IPv6
addresses of the CEs through LDP signaling. addresses of the CEs through LDP signaling.
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If the pseudowire is only carrying IPv6 traffic, the address If the pseudowire is only carrying IPv6 traffic, the address
specified in the IP Address List TLV will always be zero. If the specified in the IP Address List TLV will always be zero. If the
pseudowire is carrying both IPv4 and IPv6 traffic, the pseudowire is carrying both IPv4 and IPv6 traffic, the
mechanisms used for IPV6 and IPv4 should not overlap. In mechanisms used for IPV6 and IPv4 should not overlap. In
particular, just because a PE has learned a link-layer address particular, just because a PE has learned a link-layer address
for IPv6 traffic by intercepting a Neighbor Advertisement from for IPv6 traffic by intercepting a Neighbor Advertisement from
its directly-connected CE, it should not assume that it can use its directly-connected CE, it should not assume that it can use
that link-layer address for IPv4 traffic until that fact is that link-layer address for IPv4 traffic until that fact is
confirmed by reception of, for example, an IPv4 ARP message from confirmed by reception of, for example, an IPv4 ARP message from
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follows. follows.
o If a pseudowire is configured for AC with IPv4 CEs only, o If a pseudowire is configured for AC with IPv4 CEs only,
the PE should advertise address list tlv with address the PE should advertise address list tlv with address
family type to be of IPv4 address. The PE should process family type to be of IPv4 address. The PE should process
the IPv4 address list TLV as described in this document. the IPv4 address list TLV as described in this document.
o If a pseudowire is configured for AC with both IPv4 and o If a pseudowire is configured for AC with both IPv4 and
IPv6 CEs, the PE should advertise IPv6 capability using IPv6 CEs, the PE should advertise IPv6 capability using
the procedures described in Section 7. below. the procedures described in Section 7. below.
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
o If a PE does not receive any address list TLV or IPv6 o If a PE does not receive any address list TLV or IPv6
capability advertisement, it MAY assume IPv4 behavior. The capability advertisement, it MAY assume IPv4 behavior. The
address resolution for IPv4 MUST then depend on local address resolution for IPv4 MUST then depend on local
manual configuration. manual configuration.
We use the Address List TLV as defined in [RFC 3036] to signal We use the Address List TLV as defined in [RFC 3036] to signal
the IPv4 address of the local CE. This IP address list TLV is the IPv4 address of the local CE. This IP address list TLV is
included in the optional parameter field of the Label Mapping included in the optional parameter field of the Label Mapping
message. message.
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IPv4 address of the CE attached to the advertising PE. The IPv4 address of the CE attached to the advertising PE. The
encoding of the individual address depends on the Address encoding of the individual address depends on the Address
Family (which may be of value zero). Family (which may be of value zero).
The following address encodings are defined by this version of The following address encodings are defined by this version of
the protocol: the protocol:
Address Family Address Encoding Address Family Address Encoding
IPv4 (1) 4 octet full IPv4 address IPv4 (1) 4 octet full IPv4 address
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The IP address field is set to all zeroes to denote that The IP address field is set to all zeroes to denote that
advertising PE has not learned the IPv4 address of its local CE. advertising PE has not learned the IPv4 address of its local CE.
Any non-zero value of the IP address field denotes the IPv4 Any non-zero value of the IP address field denotes the IPv4
address of advertising PE's attached CE device. address of advertising PE's attached CE device.
The IPv4 address of the CE is also supplied in the optional The IPv4 address of the CE is also supplied in the optional
parameters field of the LDP Notification message along with the parameters field of the LDP Notification message along with the
PW FEC. The LDP Notification message is used to signal any PW FEC. The LDP Notification message is used to signal any
change in the status of the CE's IPv4 address. change in the status of the CE's IPv4 address.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID | | Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (TLV) | | Status (TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address List TLV (as defined above) | | IP Address List TLV (as defined above) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWId FEC or Generalized ID FEC | | PWId FEC or Generalized ID FEC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Status TLV status code is set to 0x00000031 "IP address of The Status TLV status code is set to 0x0000002C "IP address of
CE", to indicate that IP Address update follows. Since this CE", to indicate that IP Address update follows. Since this
notification does not refer to any particular message the notification does not refer to any particular message the
Message Id, and Message Type fields are set to 0. [note: Status Message Id, and Message Type fields are set to 0. [note: Status
Code 0x00000031 is pending IANA allocation]. Code 0x0000002C is pending IANA allocation].
The PW FEC TLV SHOULD not include the interface parameters as The PW FEC TLV SHOULD not include the interface parameters as
they are ignored in the context of this message. they are ignored in the context of this message.
7. IPv6 Capability Advertisement 7. IPv6 Capability Advertisement
A 'Stack Capability' Interface Parameter sub-TLV is signaled by A 'Stack Capability' Interface Parameter sub-TLV is signaled by
the two PEs so that they can agree which stack(s) they should be the two PEs so that they can agree which stack(s) they should be
using. It is assumed by default that the IP PW will always be using. It is assumed by default that the IP PW will always be
capable of carrying IPv4 packets. Thus this capability sub-TLV capable of carrying IPv4 packets. Thus this capability sub-TLV
is used to indicate if other stacks need to be supported is used to indicate if other stacks need to be supported
concurrently with IPv4. concurrently with IPv4.
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
The 'Stack Capability' sub-TLV is part of the interface The 'Stack Capability' sub-TLV is part of the interface
parameters of the PW FEC. The proposed format for the Stack parameters of the PW FEC. The proposed format for the Stack
Capability interface parameter sub-TLV is as follows: Capability interface parameter sub-TLV is as follows:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter ID | Length | Stack Capability | | Parameter ID | Length | Stack Capability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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received from the far end PE is not set to all zeros, then the received from the far end PE is not set to all zeros, then the
sub-TLV MUST be treated as invalid and the PE MUST release the sub-TLV MUST be treated as invalid and the PE MUST release the
PW label. PW label.
The behavior of a PE that does not understand an interface The behavior of a PE that does not understand an interface
parameter sub-TLV is specified in RFC4447 [RFC4447]. parameter sub-TLV is specified in RFC4447 [RFC4447].
8. IANA Considerations 8. IANA Considerations
8.1. LDP Status messages 8.1. LDP Status messages
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This document uses new LDP status codes, IANA already maintains This document uses new LDP status codes, IANA already maintains
a registry of name "STATUS CODE NAME SPACE" defined by [RFC a registry of name "STATUS CODE NAME SPACE" defined by [RFC
3036]. The following values are suggested for assignment: 3036]. The following values are suggested for assignment:
0x00000031 "IP Address of CE" 0x0000002C "IP Address of CE"
8.2. Interface Parameters 8.2. Interface Parameters
This document proposes a new Interface Parameters sub-TLV, to be This document proposes a new Interface Parameters sub-TLV, to be
assigned from the 'Pseudowire Interface Parameters Sub-TLV type assigned from the 'Pseudowire Interface Parameters Sub-TLV type
Registry'. The following value is suggested for the Parameter ID: Registry'. The following value is suggested for the Parameter ID:
0x16 "Stack capability" 0x16 "Stack capability"
IANA is also requested to set up a registry of "L2VPN PE stack IANA is also requested to set up a registry of "L2VPN PE stack
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9. Use of IGPs with IP L2 Interworking L2VPNs 9. Use of IGPs with IP L2 Interworking L2VPNs
In an IP L2 interworking L2VPN, when an IGP on a CE connected to In an IP L2 interworking L2VPN, when an IGP on a CE connected to
a broadcast link is cross-connected with an IGP on a CE a broadcast link is cross-connected with an IGP on a CE
connected to a point-to-point link, there are routing protocol connected to a point-to-point link, there are routing protocol
related issues that must be addressed. The link state routing related issues that must be addressed. The link state routing
protocols are cognizant of the underlying link characteristics protocols are cognizant of the underlying link characteristics
and behave accordingly when establishing neighbor adjacencies, and behave accordingly when establishing neighbor adjacencies,
representing the network topology, and passing protocol packets. representing the network topology, and passing protocol packets.
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9.1. OSPF 9.1. OSPF
The OSPF protocol treats a broadcast link type with a special The OSPF protocol treats a broadcast link type with a special
procedure that engages in neighbor discovery to elect a procedure that engages in neighbor discovery to elect a
designated and a backup designated router (DR and BDR designated and a backup designated router (DR and BDR
respectively) with which each other router on the link forms respectively) with which each other router on the link forms
adjacencies. However, these procedures are neither applicable adjacencies. However, these procedures are neither applicable
nor understood by OSPF running on a point-to-point link. By nor understood by OSPF running on a point-to-point link. By
cross-connecting two neighbors with disparate link types, an IP cross-connecting two neighbors with disparate link types, an IP
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described in section 5.1, the attached PE can learn the local CE described in section 5.1, the attached PE can learn the local CE
router's IP address from the IP header of its advertisements. No router's IP address from the IP header of its advertisements. No
special configuration is required for RIP in this type of Layer special configuration is required for RIP in this type of Layer
2 IP Interworking L2VPN. 2 IP Interworking L2VPN.
9.3. IS-IS 9.3. IS-IS
The IS-IS protocol does not encapsulate its PDUs in IP, and The IS-IS protocol does not encapsulate its PDUs in IP, and
hence cannot be supported in IP L2 Interworking L2VPNs. hence cannot be supported in IP L2 Interworking L2VPNs.
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
10. Multi-domain considerations 10. Multi-domain considerations
In a back-to-back configuration, when two PEs are connected with In a back-to-back configuration, when two PEs are connected with
Ethernet, the ARP proxy function has limited application as Ethernet, the ARP proxy function has limited application as
there is no local CE. there is no local CE.
| |
Network A | Network B Network A | Network B
CE-1 <---> PE-1 <---> PE-2 <===> PE-3 <---> PE-4 <---> CE-2 CE-1 <---> PE-1 <---> PE-2 <===> PE-3 <---> PE-4 <---> CE-2
ATM LDP ETH LDP ETH ATM LDP ETH LDP ETH
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o Configure CE2's IP address as a local CE's IP address at o Configure CE2's IP address as a local CE's IP address at
PE2 and CE1's IP address as local CE's IP address at PE3. PE2 and CE1's IP address as local CE's IP address at PE3.
Additionally, PE2 and PE3 are required to generate ARP Additionally, PE2 and PE3 are required to generate ARP
requests using their own MAC addresses as the source requests using their own MAC addresses as the source
address. These PEs are in effect proxying for CEs present address. These PEs are in effect proxying for CEs present
in the each other's network. This is not a desirable in the each other's network. This is not a desirable
option as it requires configuration of IP address of a CE option as it requires configuration of IP address of a CE
that is present in others (possibly other service that is present in others (possibly other service
provider's) network. provider's) network.
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
o In the second option, PE2 and PE3 use gratuitous ARP which o In the second option, PE2 and PE3 use gratuitous ARP which
eliminates configuration of IP addresses of the CEs. In eliminates configuration of IP addresses of the CEs. In
this scheme, when PE2 learns the IP address of CE1 this scheme, when PE2 learns the IP address of CE1
(through LDP signaling), PE2 sends a gratuitous ARP to PE3 (through LDP signaling), PE2 sends a gratuitous ARP to PE3
with the source and destination IP address field set to with the source and destination IP address field set to
CE1's IP address and the source MAC address field set to CE1's IP address and the source MAC address field set to
PE2's MAC address. When PE3 learns the IP address of CE1 PE2's MAC address. When PE3 learns the IP address of CE1
(from the gratuitous ARP), PE3 notifies PE4 of the IP (from the gratuitous ARP), PE3 notifies PE4 of the IP
address of the CE1 through LDP signaling. Similarly, for address of the CE1 through LDP signaling. Similarly, for
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pseudowire options may prevent mis-wiring due to configuration pseudowire options may prevent mis-wiring due to configuration
errors. errors.
Learning the IP address of the appropriate CE can be a security Learning the IP address of the appropriate CE can be a security
issue. It is expected that the Attachment Circuit to the local issue. It is expected that the Attachment Circuit to the local
CE will be physically secured. If this is a concern, the PE must CE will be physically secured. If this is a concern, the PE must
be configured with IP and MAC address of the CE when connected be configured with IP and MAC address of the CE when connected
with Ethernet or IP and virtual circuit information (DLCI or with Ethernet or IP and virtual circuit information (DLCI or
VPI/VCI when connected over Frame Relay or ATM and IP address VPI/VCI when connected over Frame Relay or ATM and IP address
only when connected over PPP). During each ARP/inARP frame only when connected over PPP). During each ARP/inARP frame
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
processing, the PE must verify the received information against processing, the PE must verify the received information against
local configuration before forwarding the information to the local configuration before forwarding the information to the
remote PE to protect against hijacking the connection. remote PE to protect against hijacking the connection.
For IPv6, the preferred means of security is Secure Neighbor For IPv6, the preferred means of security is Secure Neighbor
Discover (SEND) [RFC3971]. SEND provides a mechanism for Discover (SEND) [RFC3971]. SEND provides a mechanism for
securing Neighbor Discovery packets over media (such as wireless securing Neighbor Discovery packets over media (such as wireless
links) that may be insecure and open to packet interception and links) that may be insecure and open to packet interception and
substitution. SEND is based upon cryptographic signatures of substitution. SEND is based upon cryptographic signatures of
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the source MAC address of the received frame against the MAC the source MAC address of the received frame against the MAC
address of the admitted connection. The frame is forwarded to PW address of the admitted connection. The frame is forwarded to PW
only when authenticity is verified. When spoofing is detected, only when authenticity is verified. When spoofing is detected,
PE must sever the connection with the local CE, tear down the PW PE must sever the connection with the local CE, tear down the PW
and start over. and start over.
12. Acknowledgements 12. Acknowledgements
The authors would like to thank Mathew Bocci, Yetik Serbest, The authors would like to thank Mathew Bocci, Yetik Serbest,
Prabhu Kavi, Bruce Lasley, Mark Lewis, Carlos Pignataro, Shane Prabhu Kavi, Bruce Lasley, Mark Lewis, Carlos Pignataro, Shane
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
Amante and other folks who participated in the discussions Amante and other folks who participated in the discussions
related to this draft. related to this draft.
13. References 13. References
13.1. Normative References 13.1. Normative References
[ARP] RFC 826, STD 37, D. Plummer, "An Ethernet Address [ARP] RFC 826, STD 37, D. Plummer, "An Ethernet Address
Resolution protocol: Or Converting Network Protocol Resolution protocol: Or Converting Network Protocol
skipping to change at page 29, line 4 skipping to change at page 29, line 4
December, 1998. December, 1998.
[RFC 3122] Conta, A., "Extensions to IPv6 Neighbor Discovery [RFC 3122] Conta, A., "Extensions to IPv6 Neighbor Discovery
for Inverse Discovery Specification", RFC 3122, for Inverse Discovery Specification", RFC 3122,
June 2001. June 2001.
[RFC 2462] Thomson, S. and Narten, T., "IPv6 Stateless [RFC 2462] Thomson, S. and Narten, T., "IPv6 Stateless
Address Autoconfiguration", RFC 2462, December Address Autoconfiguration", RFC 2462, December
1998. 1998.
[RFC 3971] Arkko, J. et al., "Secure Neighbor Discovery [RFC 3971] Arkko, J. et al., "Secure Neighbor Discovery
(SEND)", RFC 3971, March 2005. (SEND)", RFC 3971, March 2005.
[RFC2434] Narten, T et al., "Guidelines for Writing an IANA [RFC2434] Narten, T et al., "Guidelines for Writing an IANA
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
13.2. Informative References 13.2. Informative References
[L2VPN-FRM] L. Andersson et al., "Framework for L2VPN", June [L2VPN-FRM] L. Andersson et al., "Framework for L2VPN", June
2004, work in progress. 2004, work in progress.
[PPP-IPCP] RFC 1332, G. McGregor, "The PPP Internet Protocol [PPP-IPCP] RFC 1332, G. McGregor, "The PPP Internet Protocol
Control Protocol (IPCP)". Control Protocol (IPCP)".
[PROXY-ARP] RFC 925, J. Postel, "Multi-LAN Address [PROXY-ARP] RFC 925, J. Postel, "Multi-LAN Address
Resolution". Resolution".
[RFC 1256] S.Deering, "ICMP Router Discovery Messages". [RFC 1256] S.Deering, "ICMP Router Discovery Messages".
skipping to change at page 30, line 4 skipping to change at page 30, line 4
BT BT
Email: giles.heron@gmail.com Email: giles.heron@gmail.com
Sunil Khandekar and Vach Kompella Sunil Khandekar and Vach Kompella
Email: sunil@timetra.com Email: sunil@timetra.com
Email: vkompella@timetra.com Email: vkompella@timetra.com
Toby Smith Toby Smith
Network Appliance, Inc. Network Appliance, Inc.
EMail: tob@netapp.com EMail: tob@netapp.com
Draft-ietf-l2vpn-arp-mediation-11.txt Draft-ietf-l2vpn-arp-mediation-12.txt
Andrew G. Malis Andrew G. Malis
Verizon Verizon
EMail: Andy.g.Malis@verizon.com EMail: Andy.g.Malis@verizon.com
Steven Wright Steven Wright
Bell South Corp Bell South Corp
Email: steven.wright@bellsouth.com Email: steven.wright@bellsouth.com
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