draft-ietf-ipv6-ndproxy-03.txt   draft-ietf-ipv6-ndproxy-04.txt 
IPv6 Working Group D. Thaler IPv6 Working Group D. Thaler
INTERNET-DRAFT M. Talwar INTERNET-DRAFT M. Talwar
July 14, 2005 Microsoft October 20, 2005 Microsoft
Expires January 2006 C. Patel Expires April 2006 C. Patel
All Play, No Work All Play, No Work
Neighbor Discovery Proxies (ND Proxy) Neighbor Discovery Proxies (ND Proxy)
<draft-ietf-ipv6-ndproxy-03.txt> <draft-ietf-ipv6-ndproxy-04.txt>
Status of this Memo Status of this Memo
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applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 2, line 5 skipping to change at page 2, line 5
progress." progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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Copyright Notice Copyright Notice
Draft ND Proxy July 2005 Draft ND Proxy October 2005
Copyright (C) The Internet Society (2005). All Rights Reserved. Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract Abstract
Bridging multiple links into a single entity has several Bridging multiple links into a single entity has several
operational advantages. A single subnet prefix is sufficient to operational advantages. A single subnet prefix is sufficient to
support multiple physical links. There is no need to allocate support multiple physical links. There is no need to allocate
subnet numbers to the different networks, simplifying management. subnet numbers to the different networks, simplifying management.
Bridging some types of media requires network-layer support, Bridging some types of media requires network-layer support,
however. This document describes these cases and specifies the however. This document describes these cases and specifies the
IP-layer support that enables bridging under these circumstances. IP-layer support that enables bridging under these circumstances.
The behavior of one common type of IPv4 ARP Proxy deployed today
is documented herein for informational purposes, but this document
concentrates on describing similar behavior for IPv6.
1. Introduction 1. Introduction
In the IPv4 Internet today, it is common for Network Address In the IPv4 Internet today, it is common for Network Address
Translators (NATs) [NAT] to be used to easily connect one or more Translators (NATs) [NAT] to be used to easily connect one or more
leaf links to an existing network without requiring any leaf links to an existing network without requiring any
coordination with the network service provider. Since NATs modify coordination with the network service provider. Since NATs modify
IP addresses in packets, they are problematic for many IP IP addresses in packets, they are problematic for many IP
applications. As a result, it is desirable to address the problem applications. As a result, it is desirable to address the problem
(for both IPv4 and IPv6) without the need for NATs, while still (for both IPv4 and IPv6) without the need for NATs, while still
maintaining the property that no explicit cooperation from the maintaining the property that no explicit cooperation from the
router is needed. router is needed.
Another common solution is IEEE 802 bridging, as specified in One common solution is IEEE 802 bridging, as specified in
[BRIDGE]. It is expected that whenever possible links will be [BRIDGE]. It is expected that whenever possible links will be
bridged at the link layer using classic bridge technology [BRIDGE] bridged at the link layer using classic bridge technology [BRIDGE]
as opposed to using the mechanisms herein. However, classic as opposed to using the mechanisms herein. However, classic
bridging at the data-link layer has the following limitations bridging at the data-link layer has the following limitations
(among others): (among others):
o It requires the ports to support promiscuous mode. o It requires the ports to support promiscuous mode.
o It requires all ports to support the same type of link-layer o It requires all ports to support the same type of link-layer
addressing (in particular, IEEE 802 addressing). addressing (in particular, IEEE 802 addressing).
As a result, two common scenarios, described below, are not As a result, two common scenarios, described below, are not
solved, and it is these two scenarios we specifically target in solved, and it is these two scenarios we specifically target in
this document. While the mechanism described herein may apply to this document. While the mechanism described herein may apply to
other scenarios as well, we will concentrate our discussion on other scenarios as well, we will concentrate our discussion on
Draft ND Proxy July 2005
these two scenarios. these two scenarios.
Draft ND Proxy October 2005
1.1. SCENARIO 1: Wireless upstream 1.1. SCENARIO 1: Wireless upstream
The following figure illustrates a likely example: The following figure illustrates a likely example:
| +-------+ +--------+ | +-------+ +--------+
local |Ethernet | | Wireless | Access | local |Ethernet | | Wireless | Access |
+---------+ A +-))) (((-+ +--> rest of network +---------+ A +-))) (((-+ +--> rest of network
hosts | | | link | Point | hosts | | | link | Point |
| +-------+ +--------+ | +-------+ +--------+
In this scenario, the access point has assigned an IPv4 and/or an In this scenario, the access point has assigned an IPv6 subnet
IPv6 subnet prefix to the wireless link, and uses link-layer prefix to the wireless link, and uses link-layer encryption so
encryption so that wireless clients may not see each other's data. that wireless clients may not see each other's data.
Classic bridging requires the bridge (node A in the above diagram) Classic bridging requires the bridge (node A in the above diagram)
to be in promiscuous mode. In this wireless scenario, A cannot to be in promiscuous mode. In this wireless scenario, A cannot
put its wireless interface into promiscuous mode, since one put its wireless interface into promiscuous mode, since one
wireless node cannot see traffic to/from other wireless nodes. wireless node cannot see traffic to/from other wireless nodes.
This document describes a solution for both IPv4 and IPv6 which
does not involve NAT or require any change to the access point or
router.
Multiple variants of IPv4 ARP proxying have been used for some IPv4 ARP proxying has been used for some years to solve this
years to solve this problem. ARP-based bridges were first problem without involving NAT or requiring any change to the
described in [ARPPROXY], but that variant decrements the TTL, does access point or router. In this document, we describe equivalent
not forward all-ones broadcasts, and requires proxies to keep per- functionality for IPv6 to remove this incentive to deploy NATs in
packet state on recent subnet broadcasts. The first two IPv6.
characteristics can cause problems with applications and protocols
which assume that nodes in the subnet prefix can be reached with
TTL 1 (or with TTL 255, with TTL 255 verified on receipt) and/or
with a subnet broadcast. The third characteristic results in
scalability issues in proxy implementations. As a result,
multiple variants have emerged in different implementations over
time. In this document, we describe one such variant, and enable
equivalent functionality for IPv6 to remove this incentive to
deploy NATs in IPv6.
We also note that Prefix Delegation [PD] could also be used to We also note that Prefix Delegation [PD] could also be used to
solve this scenario. There are, however, two disadvantages to solve this scenario. There are, however, two disadvantages to
this. First, if an implementation already supports IPv4 ARP this. First, if an implementation already supports IPv4 ARP
proxying (which is indeed supported in a number of implementations proxying (which is indeed the case in a number of implementations
today), then IPv6 Prefix Delegation would result in separate IPv6 today), then IPv6 Prefix Delegation would result in separate IPv6
Draft ND Proxy July 2005
subnets on either side of the device, while a single IPv4 subnet subnets on either side of the device, while a single IPv4 subnet
would span both segments. This topological discrepancy can would span both segments. This topological discrepancy can
complicate applications and protocols which use the concept of a complicate applications and protocols which use the concept of a
local subnet. Secondly, the extent to which Prefix Delegation is local subnet. Secondly, the extent to which Prefix Delegation is
supported, and supported without additional charge, is up to the supported, and supported without additional charge, is up to the
service provider. Hence, there is no guarantee that Prefix service provider. Hence, there is no guarantee that Prefix
Delegation will work without explicit configuration or additional Delegation will work without explicit configuration or additional
charge. Bridging, on the other hand, allows the device to work charge. Bridging, on the other hand, allows the device to work
with zero configuration, regardless of the service provider's with zero configuration, regardless of the service provider's
policies, just as a NAT does. Hence bridging avoids the incentive policies, just as a NAT does. Hence bridging avoids the incentive
to NAT IPv6 just to avoid paying for, or requiring configuration to NAT IPv6 just to avoid paying for, or requiring configuration
to get, another prefix. to get, another prefix.
Draft ND Proxy October 2005
1.2. SCENARIO 2: PPP upstream 1.2. SCENARIO 2: PPP upstream
The following figure illustrates another likely example: The following figure illustrates another likely example:
| +-------+ +--------+ | +-------+ +--------+
local |Ethernet | | PPP link | | local |Ethernet | | PPP link | |
+---------+ A +-----------+ Router +--> rest of network +---------+ A +-----------+ Router +--> rest of network
hosts | | | | | hosts | | | | |
| +-------+ +--------+ | +-------+ +--------+
In this scenario, the router believes that the other end of the In this scenario, the router has assigned a /64 to the PPP link
PPP link (node A) has a single IPv4 address, as negotiated by PPP. and advertises it in an IPv6 Router Advertisement.
For IPv6, it has assigned a /64 to the link and advertises it in
an IPv6 Router Advertisement.
Classic bridging does not support non-802 media, and hence IPv4 Classic bridging does not support non-802 media. The PPP Bridging
connectivity is solved by making the proxy (node A in the above Control Protocol [BCP] defines a mechanism for supporting bridging
diagram) be a NAT. This document does not specify any other IPv4 over PPP, but it requires both ends to be configured to support
solution for this scenario. However, this document does specify a it. Hence IPv4 connectivity is often solved by making the proxy
solution for IPv6 which does not involve NAT or require any change (node A in the above diagram) be a NAT or an IPv4 ARP Proxy. This
to the router. document specifies a solution for IPv6 which does not involve NAT
or require any change to the router.
1.3. Inapplicable Scenarios
This document is not applicable to scenarios with loops in the
physical topology, or where routers exist on multiple segments.
These cases are detected and proxying is disabled (see Section 6).
In addition, this document is not appropriate for scenarios where
classic bridging can be applied, or when configuration of the
router can be done.
2. Terminology 2. Terminology
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 "OPTIONAL" NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in BCP 14, RFC in this document are to be interpreted as described in BCP 14, RFC
2119 [KEYWORDS]. 2119 [KEYWORDS].
The term "proxy interface" will be used to refer to an interface The term "proxy interface" will be used to refer to an interface
(which could itself be a bridge interface) over which network (which could itself be a bridge interface) over which network
layer proxying is done as defined herein. layer proxying is done as defined herein.
Draft ND Proxy July 2005
In this document we make no distinction between a "link" (in the In this document we make no distinction between a "link" (in the
classic IPv6 sense) and a "subnet". We use the term "segment" to classic IPv6 sense) and a "subnet". We use the term "segment" to
apply to a bridged component of the link. apply to a bridged component of the link.
Draft ND Proxy October 2005
Finally, while it is possible that functionality equivalent to Finally, while it is possible that functionality equivalent to
that described herein may be achieved by nodes which do not that described herein may be achieved by nodes which do not
fulfill all the requirements in [NODEREQ], in the remainder of fulfill all the requirements in [NODEREQ], in the remainder of
this document we will describe behavior in terms of an IPv6 node this document we will describe behavior in terms of an IPv6 node
as defined in that document. as defined in that document.
3. Requirements 3. Requirements
Proxy behavior is designed with the following requirements in Proxy behavior is designed with the following requirements in
mind: mind:
o Support connecting multiple segments with a single subnet o Support connecting multiple segments with a single subnet
prefix. prefix.
o Support media which cannot be bridged at the link-layer. o Support media which cannot be bridged at the link-layer.
Note, this document does not support bridging of non-802
media for IPv4.
o Support both IPv6 and IPv4 for 802 media.
o Do not require any changes to existing routers. That is, any o Do not require any changes to existing routers. That is,
routers on the subnet should be unaware that the subnet is routers on the subnet may be unaware that the subnet is being
being bridged. bridged.
o Provide full connectivity between all nodes in the subnet. o Provide full connectivity between all nodes in the subnet.
For example, if there are existing nodes (such as any routers For example, if there are existing nodes (such as any routers
on the subnet) which have addresses in the subnet prefix, on the subnet) which have addresses in the subnet prefix,
adding a proxy must allow bridged nodes to have full adding a proxy must allow bridged nodes to have full
connectivity with existing nodes on the subnet. connectivity with existing nodes on the subnet.
o Prevent loops. o Prevent loops.
o Also work in the absence of any routers. o Also work in the absence of any routers.
o Support nodes moving between segments. For example, a node o Support nodes moving between segments. For example, a node
should be able to keep its address without seeing its address should be able to keep its address without seeing its address
as a duplicate due to any cache maintained at the proxy. as a duplicate due to any cache maintained at the proxy.
o Allow dynamic addition of a proxy without adversely o Allow dynamic addition of a proxy without adversely
disrupting the network. disrupting the network.
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o The proxy behavior should not break any existing classic o The proxy behavior should not break any existing classic
bridges in use on a network segment. bridges in use on a network segment.
Draft ND Proxy October 2005
3.1. Non-requirements 3.1. Non-requirements
The following items are not considered requirements, as they are The following items are not considered requirements, as they are
not met by classic bridges: not met by classic bridges:
o Show up as a hop in a traceroute. o Show up as a hop in a traceroute.
o Use the shortest path between two nodes on different o Use the shortest path between two nodes on different
segments. segments.
skipping to change at page 6, line 33 skipping to change at page 6, line 30
o Support connecting media on which Neighbor Discovery is not o Support connecting media on which Neighbor Discovery is not
possible. For example, some technologies such as [6TO4] use possible. For example, some technologies such as [6TO4] use
an algorithmic mapping from IPv6 address to the underlying an algorithmic mapping from IPv6 address to the underlying
link-layer (IPv4 in this case) address, and hence cannot link-layer (IPv4 in this case) address, and hence cannot
support bridging arbitrary IP addresses. support bridging arbitrary IP addresses.
The following additional items are not considered requirements for The following additional items are not considered requirements for
this document: this document:
o Support network-layer protocols other than IPv4 and IPv6. We o Support network-layer protocols other than IPv6. We do not
do not preclude such support, but it is not specified in this preclude such support, but it is not specified in this
document. document.
o Support Neighbor Discovery, Router Discovery, or DHCPv4
packets using IPsec. We also note that the current methods
for securing these protocols do not use IPsec so this is
considered acceptable.
o Support Redirects for off-subnet destinations that point to a o Support Redirects for off-subnet destinations that point to a
router on a different segment from the redirected host. router on a different segment from the redirected host.
While this scenario may be desirable, no solution is While this scenario may be desirable, no solution is
currently known which does not have undesirable side effects currently known which does not have undesirable side effects
outside the subnet. As a result, this scenario is outside outside the subnet. As a result, this scenario is outside
the scope of this document. the scope of this document.
Draft ND Proxy July 2005
4. Proxy Behavior 4. Proxy Behavior
Network layer support for proxying between multiple interfaces Network layer support for proxying between multiple interfaces
SHOULD be used only when classic bridging is not possible. SHOULD be used only when classic bridging is not possible.
When a proxy interface comes up, the node puts it in "all- When a proxy interface comes up, the node puts it in "all-
multicast" mode so that it will receive all multicast packets. It multicast" mode so that it will receive all multicast packets. It
is common for interfaces to not support full promiscuous mode is common for interfaces to not support full promiscuous mode
(e.g., on a wireless client), but all-multicast mode is generally (e.g., on a wireless client), but all-multicast mode is generally
still supported. still supported.
As with all other interfaces, IPv4 and IPv6 maintain a neighbor Draft ND Proxy October 2005
cache (aka "ARP cache") for each proxy interface, which will be
used as described below. For readability, we will describe the As with all other interfaces, IPv6 maintains a neighbor cache for
neighbor cache as if both IPv4 and IPv6 neighbors use the same each proxy interface, which will be used as described below.
state machine described in [ND].
4.1. Forwarding Packets 4.1. Forwarding Packets
When a packet from any IP source address other than the When a packet from any IPv6 source address other than the
unspecified address is received on a proxy interface, the neighbor unspecified address is received on a proxy interface, the neighbor
cache of that interface SHOULD be consulted to find an entry for cache of that interface SHOULD be consulted to find an entry for
the source IP address. If no entry exists, one is created in the the source IPv6 address. If no entry exists, one is created in
STALE state. the STALE state.
When any IP or ARP packet is received on a proxy interface, it When any IPv6 packet is received on a proxy interface, it must be
must be parsed to see whether it is known to be of a type that parsed to see whether it is known to be of a type that negotiates
negotiates link-layer addresses. This document covers the link-layer addresses. This document covers the following types:
following types: ARP, IPv6 Neighbor Discovery, IPv6 Router Neighbor Solicitations, Neighbor Advertisements, Router
Discovery, IPv6 Redirects, and DHCPv4. These packets are ones Advertisements, and Redirects. These packets are ones that can
that can carry link-layer addresses, and hence must be proxied (as carry link-layer addresses, and hence must be proxied (as
described below) so that packets between nodes on different described below) so that packets between nodes on different
segments can be received by the proxy and have the correct link- segments can be received by the proxy and have the correct link-
layer address type on each segment. layer address type on each segment.
When any other IP broadcast or multicast packet is received on a When any other IPv6 multicast packet is received on a proxy
proxy interface, in addition to any normal IP behavior such as interface, in addition to any normal IPv6 behavior such as being
being delivered locally, it is forwarded unchanged (other than delivered locally, it is forwarded unchanged (other than using a
using a new link-layer header) out all other proxy interfaces on new link-layer header) out all other proxy interfaces on the same
the same link. (As specified in [BRIDGE], the proxy may instead link. (As specified in [BRIDGE], the proxy may instead support
support multicast learning and filtering but this is OPTIONAL.) multicast learning and filtering but this is OPTIONAL.) In
In particular, the IPv4 TTL or IPv6 Hop Limit is not updated, and particular, the IPv6 Hop Limit is not updated, and no ICMP errors
no ICMP errors (except as noted in Section 4.1.1 below) are sent (except as noted in Section 4.1.1 below) are sent as a result of
as a result of attempting this forwarding. attempting this forwarding.
Draft ND Proxy July 2005
When any other IP unicast packet is received on a proxy interface, When any other IPv6 unicast packet is received on a proxy
if it is not locally destined then it is forwarded unchanged interface, if it is not locally destined then it is forwarded
(other than using a new link-layer header) to the proxy interface unchanged (other than using a new link-layer header) to the proxy
for which the next hop address appears in the neighbor cache. interface for which the next hop address appears in the neighbor
Again the IPv4 TTL or IPv6 Hop Limit is not updated, and no ICMP cache. Again the IPv6 Hop Limit is not updated, and no ICMP
errors (except as noted in Section 4.1.1 below) are sent as a errors (except as noted in Section 4.1.1 below) are sent as a
result of attempting this forwarding. To choose a proxy interface result of attempting this forwarding. To choose a proxy interface
to forward to, the neighbor cache is consulted, and the interface to forward to, the neighbor cache is consulted, and the interface
with the neighbor entry in the "best" state is used. In order of with the neighbor entry in the "best" state is used. In order of
least to most preferred, the states (per [ND]) are INCOMPLETE, least to most preferred, the states (per [ND]) are INCOMPLETE,
STALE, DELAY, PROBE, REACHABLE. A packet is never forwarded back STALE, DELAY, PROBE, REACHABLE. A packet is never forwarded back
out the same interface on which it arrived; such a packet is out the same interface on which it arrived; such a packet is
instead silently dropped. instead silently dropped.
Draft ND Proxy October 2005
If no cache entry exists (as may happen if the proxy has If no cache entry exists (as may happen if the proxy has
previously evicted the cache entry or if the proxy is restarted), previously evicted the cache entry or if the proxy is restarted),
the proxy SHOULD queue the packet and initiate Neighbor Discovery the proxy SHOULD queue the packet and initiate Neighbor Discovery
as if the packet were being locally generated. The proxy MAY as if the packet were being locally generated. The proxy MAY
instead silently drop the packet. In this case, the entry will instead silently drop the packet. In this case, the entry will
eventually be recreated when the sender re-attempts neighbor eventually be recreated when the sender re-attempts neighbor
discovery. discovery.
The link layer header, and the link-layer address within the The link layer header, and the link-layer address within the
payload for each forwarded packet will be modified as follows: payload for each forwarded packet will be modified as follows:
1) The source address will be the address of the outgoing 1) The source address will be the address of the outgoing
interface. interface.
2) The destination address will be the address in the neighbor 2) The destination address will be the address in the neighbor
entry corresponding to the destination IP address. entry corresponding to the destination IPv6 address.
3) The link-layer address within the payload is substituted with 3) The link-layer address within the payload is substituted with
the address of the outgoing interface. the address of the outgoing interface.
4.1.1. Sending Packet Too Big Messages 4.1.1. Sending Packet Too Big Messages
Whenever any IPv4 packet is to be forwarded out an interface whose Whenever any IPv6 packet is to be forwarded out an interface whose
MTU is smaller than the size of the packet, and the Dont Fragment MTU is smaller than the size of the packet, the ND proxy drops the
bit is set, the ARP proxy drops the packet and sends a packet and sends a Packet Too Big message back to the source, as
Fragmentation Needed message back to the source. described in [ICMPv6].
Similarly, whenever any IPv6 packet is to be forwarded out an
interface whose MTU is smaller than the size of the packet, the ND
proxy drops the packet and sends a Packet Too Big message back to
Draft ND Proxy July 2005
the source, as described in [ICMPv6].
4.1.2. Proxying Packets With Link-Layer Addresses 4.1.2. Proxying Packets With Link-Layer Addresses
Once it is determined that the packet is either Once it is determined that the packet is either multicast or else
multicast/broadcast or else is not locally destined (if unicast), is not locally destined (if unicast), the special types enumerated
the special types enumerated above (ARP, etc.) that carry link- above (ARP, etc.) that carry link-layer addresses are handled by
layer addresses are handled by generating a proxy packet that generating a proxy packet that contains the proxy's link-layer
contains the proxy's link-layer address on the outgoing interface address on the outgoing interface instead. Such link-layer
instead. Section 7, "Guidelines to proxy developers", describes addresses occur in the link-layer header itself, as well as in the
the scenarios in which the link-layer address substitution in the payloads of some protocols. As with all forwarded packets, the
payload should be performed. link-layer header is new.
As with all forwarded packets, the link-layer header is also new.
Note that any change to the length of a proxied packet, such as
when the link-layer address length changes, will require
corresponding changes to fields in the IP header, namely the IPv4
Total Length and Header Checksum fields, or the IPv6 Payload
Length field.
4.1.3. IPv4 ARP Proxying
When any IPv4 or ARP packet is received on a proxy interface, it
must be parsed to see whether it is known to be one of the
following types: ARP, or DHCPv4.
4.1.3.1. ARP REQUEST Packets
If the received packet is an ARP REQUEST, the request is processed
locally but no ARP REPLY is generated immediately. Instead, the
ARP REQUEST is proxied (as described above) and the ARP REPLY will
be proxied when it is received. This ensures that the proxy does
not interfere with hosts moving from one segment to another since
it never responds to an ARP REQUEST based on its own cache.
4.1.3.2. ARP REPLY Packets
If the received packet is an ARP REPLY, the neighbor cache on the
receiving interface is first updated as if the ARP REPLY were
locally destined, and then the ARP REPLY is proxied as described
above.
Draft ND Proxy July 2005
4.1.3.3. DHCPv4 Packets Section 4.1.3 enumerates the currently known cases where link-
layer addresses must be changed in payloads. For guidance on
handling future protocols, Section 7, "Guidelines to proxy
developers", describes the scenarios in which the link-layer
address substitution in the payload should be performed. Note
If the received packet is a DHCPv4 DISCOVER or REQUEST message, Draft ND Proxy October 2005
then instead of changing the client's hardware address in the
payload, the BROADCAST (B) flag is set in the proxied packet.
This ensures that the proxy will be able to receive and proxy the
response since the response will be broadcast rather than unicast
to that hardware address. The hardware address is thus used only
as a unique identifier and hence need not be a link-layer address
on the same segment.
One limitation of this rule is that if the authentication protocol that any change to the length of a proxied packet, such as when
for DHCPv4 described in [DHCPAUTH] is used, only clients that set the link-layer address length changes, will require a
the BROADCAST flag themselves will be able to use DHCPv4 through corresponding change to the IPv6 Payload Length field.
the proxy. If [DHCPAUTH] is not used, a DHCPv4 client might still
detect, with previously undefined behavior, that the broadcast bit
has been changed from the setting in the message originally set by
the client. However, the point of this rule is not to solve this
problem, but rather to document existing practice.
4.1.4. IPv6 ND Proxying 4.1.3. IPv6 ND Proxying
When any IPv6 packet is received on a proxy interface, it must be When any IPv6 packet is received on a proxy interface, it must be
parsed to see whether it is known to be one of the following parsed to see whether it is known to be one of the following
types: IPv6 Neighbor Discovery, IPv6 Router Discovery, or IPv6 types: Neighbor Solicitation, Neighbor Advertisement, Router
Redirects. Advertisement, or Redirect.
4.1.4.1. ICMPv6 Neighbor Solicitations 4.1.3.1. ICMPv6 Neighbor Solicitations
If the received packet is an ICMPv6 Neighbor Solicitation, the NS If the received packet is an ICMPv6 Neighbor Solicitation (NS),
is processed locally as described in section 7.2.3 of [ND] but no the NS is processed locally as described in section 7.2.3 of [ND]
NA is generated immediately. Instead the NS is proxied as but no NA is generated immediately. Instead the NS is proxied as
described above and the NA will be proxied when it is received. described above and the NA will be proxied when it is received.
This ensures that the proxy does not interfere with hosts moving This ensures that the proxy does not interfere with hosts moving
from one segment to another since it never responds to an NS based from one segment to another since it never responds to an NS based
on its own cache. on its own cache.
4.1.4.2. ICMPv6 Neighbor Advertisements 4.1.3.2. ICMPv6 Neighbor Advertisements
If the received packet is an ICMPv6 Neighbor Advertisement, the
neighbor cache on the receiving interface is first updated as if
the NA were locally destined, and then the NA is proxied as
Draft ND Proxy July 2005
described above. If the received packet is an ICMPv6 Neighbor Advertisement (NA),
the neighbor cache on the receiving interface is first updated as
if the NA were locally destined, and then the NA is proxied as
described in 4.1.2 above.
4.1.4.3. ICMPv6 Router Advertisements 4.1.3.3. ICMPv6 Router Advertisements
The following special processing is done for IPv6 Router The following special processing is done for IPv6 Router
Advertisements (RAs). Advertisements (RAs).
A new "Proxy" bit is defined in the existing Router Advertisement A new "Proxy" bit is defined in the existing Router Advertisement
flags field as follows: flags field as follows:
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|M|O|H|Prf|P|Rsv| |M|O|H|Prf|P|Rsv|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
where "P" indicates the location of the Proxy bit, and "Rsv where "P" indicates the location of the Proxy bit, and "Rsv
indicates the remaining reserved bits. indicates the remaining reserved bits.
Draft ND Proxy October 2005
The proxy determines an "upstream" proxy interface, typically The proxy determines an "upstream" proxy interface, typically
through a physical choice dictated by the scenario (see Scenarios through a (zero-configuration) physical choice dictated by the
1 and 2 above), or through manual configuration. scenario (see Scenarios 1 and 2 above), or through manual
configuration.
When an RA with the P bit clear arrives on the upstream interface, When an RA with the P bit clear arrives on the upstream interface,
the P bit is set when the RA is proxied out all other the P bit is set when the RA is proxied out all other
("downstream") proxy interfaces (see secion 6). ("downstream") proxy interfaces (see section 6).
If an RA with the P bit set has arrived on a given interface If an RA with the P bit set has arrived on a given interface
(including the upstream interface) within the last 60 minutes, (including the upstream interface) within the last 60 minutes,
that interface MUST NOT be used as a proxy interface; i.e., proxy that interface MUST NOT be used as a proxy interface; i.e., proxy
functionality is disabled on that interface. functionality is disabled on that interface.
Furthermore, if any RA (regardless of the value of the P bit) has Furthermore, if any RA (regardless of the value of the P bit) has
arrived on a "downstream" proxy interface within the last 60 arrived on a "downstream" proxy interface within the last 60
minutes, that interface MUST NOT be used as a proxy interface. minutes, that interface MUST NOT be used as a proxy interface.
4.1.4.4. ICMPv6 Redirects The RA is processed locally as well as proxied as described in
section 4.1.2, unless such proxying is disabled as noted above.
4.1.3.4. ICMPv6 Redirects
If the received packet is an ICMPv6 Redirect message, then the If the received packet is an ICMPv6 Redirect message, then the
proxied packet should be modified as follows. If the proxy has a proxied packet should be modified as follows. If the proxy has a
valid (i.e., not INCOMPLETE) neighbor entry for the target address valid (i.e., not INCOMPLETE) neighbor entry for the target address
on the same interface as the redirected host, then the TLLA option on the same interface as the redirected host, then the TLLA option
in the proxied Redirect simply contains the link-layer address of in the proxied Redirect simply contains the link-layer address of
the target as found in the proxy's neighbor entry, since the the target as found in the proxy's neighbor entry, since the
redirected host may reach the target address directly. Otherwise, redirected host may reach the target address directly. Otherwise,
if the proxy has a valid neighbor entry for the target address on if the proxy has a valid neighbor entry for the target address on
some other interface, then the TLLA option in the proxied packet some other interface, then the TLLA option in the proxied packet
Draft ND Proxy July 2005
contains the link-layer address of the proxy on the sending contains the link-layer address of the proxy on the sending
interface, since the redirected host must reach the target address interface, since the redirected host must reach the target address
through the proxy. Otherwise, the proxy has no valid neighbor through the proxy. Otherwise, the proxy has no valid neighbor
entry for the target address, and the proxied packet contains no entry for the target address, and the proxied packet contains no
TLLA option, which will cause the redirected host to perform TLLA option, which will cause the redirected host to perform
neighbor discovery for the target address. neighbor discovery for the target address.
4.2. Originating Packets 4.2. Originating Packets
Locally originated packets that are sent on a proxy interface also Locally originated packets that are sent on a proxy interface also
follow the same rules as packets received on a proxy interface. follow the same rules as packets received on a proxy interface.
Draft ND Proxy October 2005
If no neighbor entry exists when a unicast packet is to be locally If no neighbor entry exists when a unicast packet is to be locally
originated, an interface can be chosen in any implementation- originated, an interface can be chosen in any implementation-
specific fashion. Once the neighbor is resolved, the actual specific fashion. Once the neighbor is resolved, the actual
interface will be discovered and the packet will be sent on that interface will be discovered and the packet will be sent on that
interface. When a multicast or broadcast packet is to be locally interface. When a multicast packet is to be locally originated,
originated, an interface can be chosen in any implementation- an interface can be chosen in any implementation-specific fashion,
specific fashion, and the packet will then be forwarded out other and the packet will then be forwarded out other proxy interfaces
proxy interfaces on the same link as described in Section 4.1 on the same link as described in Section 4.1 above.
above.
5. Example 5. Example
Consider the following topology, where A and B are nodes on Consider the following topology, where A and B are nodes on
separate segments which are connected by a proxy P: separate segments which are connected by a proxy P:
A---|---P---|---B A---|---P---|---B
a p1 p2 b a p1 p2 b
A and B have link-layer addresses a and b, respectively. P has A and B have link-layer addresses a and b, respectively. P has
skipping to change at page 13, line 4 skipping to change at page 11, line 38
A first does a route lookup on the destination address B. This A first does a route lookup on the destination address B. This
matches the on-link subnet prefix, and a destination cache entry matches the on-link subnet prefix, and a destination cache entry
is created as well as a neighbor cache entry in the INCOMPLETE is created as well as a neighbor cache entry in the INCOMPLETE
state. Before the packet can be sent, A needs to resolve B's state. Before the packet can be sent, A needs to resolve B's
link-layer address and sends a Neighbor Solicitation (NS) to the link-layer address and sends a Neighbor Solicitation (NS) to the
solicited-node multicast address for B. The SLLA option in the solicited-node multicast address for B. The SLLA option in the
solicitation contains A's link-layer address. solicitation contains A's link-layer address.
P receives the solicitation (since it is receiving all link-layer P receives the solicitation (since it is receiving all link-layer
Draft ND Proxy July 2005
multicast packets) and processes it as it would any multicast multicast packets) and processes it as it would any multicast
packet by forwarding it out to other segments on the link. packet by forwarding it out to other segments on the link.
However, before actually sending the packet, it determines if the However, before actually sending the packet, it determines if the
packet being sent is one which requires proxying. Since it is an packet being sent is one which requires proxying. Since it is an
NS, it creates a neighbor entry for A on interface 1 and records NS, it creates a neighbor entry for A on interface 1 and records
its link-layer address. It also creates a neighbor entry for B its link-layer address. It also creates a neighbor entry for B
(on an arbitrary proxy interface) in the INCOMPLETE state. Since (on an arbitrary proxy interface) in the INCOMPLETE state. Since
the packet is multicast, P then needs to proxy the NS out all the packet is multicast, P then needs to proxy the NS out all
other proxy interfaces on the subnet. Before sending the packet other proxy interfaces on the subnet. Before sending the packet
out interface 2, it replaces the link-layer address in the SLLA out interface 2, it replaces the link-layer address in the SLLA
option with its own link-layer address, p2. option with its own link-layer address, p2.
B receives this NS, processing it as usual. Hence it creates a B receives this NS, processing it as usual. Hence it creates a
Draft ND Proxy October 2005
neighbor entry for A mapping it to the link-layer address p2. It neighbor entry for A mapping it to the link-layer address p2. It
responds with a Neighbor Advertisement (NA) sent to A containing responds with a Neighbor Advertisement (NA) sent to A containing
B's link-layer address b. The NA is sent using A's neighbor B's link-layer address b. The NA is sent using A's neighbor
entry, i.e. to the link-layer address p2. entry, i.e. to the link-layer address p2.
The NA is received by P, which then processes it as it would any The NA is received by P, which then processes it as it would any
unicast packet; i.e., it forwards this out interface 1, based on unicast packet; i.e., it forwards this out interface 1, based on
the neighbor cache. However, before actually sending the packet the neighbor cache. However, before actually sending the packet
out, it inspects it to determine if the packet being sent is one out, it inspects it to determine if the packet being sent is one
which requires proxying. Since it is an NA, it updates its which requires proxying. Since it is an NA, it updates its
skipping to change at page 13, line 43 skipping to change at page 12, line 30
p1. The packet is then sent out interface 1. p1. The packet is then sent out interface 1.
A receives this NA, processing it as usual. Hence it creates a A receives this NA, processing it as usual. Hence it creates a
neighbor entry for B on interface 2 in the REACHABLE state and neighbor entry for B on interface 2 in the REACHABLE state and
records the link-layer address p1. records the link-layer address p1.
6. Loop Prevention 6. Loop Prevention
An implementation MUST ensure that loops are prevented by using An implementation MUST ensure that loops are prevented by using
the P bit in RA's as follows. The proxy determines an "upstream" the P bit in RA's as follows. The proxy determines an "upstream"
proxy interface, typically through a physical choice dictated by proxy interface, typically through a (zero-configuration) physical
the scenario (see Scenarios 1 and 2 above), or through manual choice dictated by the scenario (see Scenarios 1 and 2 above), or
configuration. As described in Section 4.1.3.3, only the upstream through manual configuration. As described in Section 4.1.3.3,
interface is allowed to receive RAs, and never from other proxies. only the upstream interface is allowed to receive RAs, and never
Proxy functionality is disabled on an interface otherwise. from other proxies. Proxy functionality is disabled on an
Finally, a proxy MUST wait until it has sent two P bit RAs on a interface otherwise. Finally, a proxy MUST wait until it has sent
given "downstream" interface before it enables forwarding on that two P bit RAs on a given "downstream" interface before it enables
interface. forwarding on that interface.
Draft ND Proxy July 2005
7. Guidelines to proxy developers 7. Guidelines to proxy developers
Proxy developers will have to accomodate protocols or protocol Proxy developers will have to accomodate protocols or protocol
options (for example, new ICMP messages) that are developed in the options (for example, new ICMP messages) that are developed in the
future, or protocols that are not mentioned in this document (for future, or protocols that are not mentioned in this document (for
example, proprietary protocols). This section prescribes example, proprietary protocols). This section prescribes
guidelines that can be used by proxy developers to accomodate guidelines that can be used by proxy developers to accomodate
protocols that are not mentioned herein. protocols that are not mentioned herein.
Draft ND Proxy October 2005
1) If a link-layer address carried in the payload of the 1) If a link-layer address carried in the payload of the
protocol can be used in the link-layer header of future protocol can be used in the link-layer header of future
messages, then the proxy should substitute it with its own messages, then the proxy should substitute it with its own
address. For example the link-layer address in NA messages is address. For example the link-layer address in NA messages is
used in the link-layer header for future messages, and, used in the link-layer header for future messages, and,
hence, the proxy substitutes it with its own address. hence, the proxy substitutes it with its own address.
For broadcast/multicast packets, the link-layer address For multicast packets, the link-layer address substituted
substituted within the payload will be different for each within the payload will be different for each outgoing
outgoing interface. interface.
2) If the link-layer address in the payload of the protocol will 2) If the link-layer address in the payload of the protocol will
never be used in any link-layer header, then the proxy should never be used in any link-layer header, then the proxy should
not substitute it with its own address. No special actions not substitute it with its own address. No special actions
are required for supporting these protocols. For example, are required for supporting these protocols. For example,
[DHCPv6] is in this category. [DHCPv6] is in this category.
8. IANA Considerations 8. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
9. Security Considerations 9. Security Considerations
Unsecured Neighbor Discovery has a number of security issues which
are discussed in detail in [PSREQ]. RFC 3971 [SEND] defines
security mechanisms that can protect Neighbor Discovery.
Proxies are susceptible to the same kind of security issues that Proxies are susceptible to the same kind of security issues that
plague hosts using unsecured Neighbor Discovery or ARP. Even if plague hosts using unsecured Neighbor Discovery. These issues
these protocols are secured, the proxies may process unsecured include hijacking traffic and denial-of-service within the subnet.
messages, and update the neighbor cache. Malicious nodes within Malicious nodes within the subnet can take advantage of this
the subnet can take advantage of this property, and hijack property, and hijack traffic. In addition, a Neighbor Discovery
traffic. The threats are discussed in detail in [PSREQ]. proxy is essentially a legitimate man-in-the-middle, which implies
that there is a need to distinguish proxies from unwanted man-in-
the-middle attackers.
As a result, securing Neighbor Discovery or ARP must take into This document does not introduce any new mechanisms for the
account the ability to proxy messages. This document does not protection of proxy neighbor discovery. That is, it does not
introduce any new requirements in this regard. provide a mechanism from authorizing certain devices to act as
proxies, and it does not provide extensions to SEND to make it
possible to use both SEND and proxies at the same time. We note
that RFC 2461 [ND] already defines the ability to proxy Neighbor
Advertisements, and extensions to SEND are already needed to cover
Draft ND Proxy July 2005 Draft ND Proxy October 2005
From an IPv6 perspective, RFC 2461 [ND] already defines the that case, independent of this document.
ability to proxy Neighbor Advertisements. Since the ND packets
must be modified whenever the link-layer address formats are Note also that the use of proxy Neighbor Discovery may render it
different (as with PPP) or promiscuous reception is not possible impossible to use SEND both on the leaf subnet and on the external
(as with 802.11), securing any solution in this space requires subnet. This because the modifications performed by the proxy
that hosts have a secure relationship with the proxy. will invalidate the RSA Signature Option in a secured Neighbor
Discovery message, and cause SEND-capable nodes to either discard
the messages or treat them as unsecured. The latter is the
desired operation when SEND is used together with this
specification, and ensures that SEND nodes within this environment
can selectively downgrade themselves to unsecure Neighbor
Discovery when proxies are present.
In the following we outline some potential paths to follow when
defining a secure proxy mechanism.
It is reasonable for nodes on the leaf subnet to have a secure It is reasonable for nodes on the leaf subnet to have a secure
relationship with the proxy, and accept ND packets from either the relationship with the proxy, and accept ND packets from either the
owner of a specific address (normal SEND), or which it can verify owner of a specific address (normal SEND), or which it can verify
are from a trusted proxy (see below). are from a trusted proxy (see below).
For nodes on the external subnet, there is a tradeoff between For nodes on the external subnet, there is a tradeoff between
security (where all nodes have a secure relationship with the security (where all nodes have a secure relationship with the
proxy) and privacy (where no nodes are aware that the proxy is a proxy) and privacy (where no nodes are aware that the proxy is a
proxy). In the case of a point-to-point external link (Scenario proxy). In the case of a point-to-point external link (Scenario
2) however, SEND may not be a requirement on that link. 2) however, SEND may not be a requirement on that link.
Verifying that ND packets come from a trusted proxy requires an Verifying that ND packets come from a trusted proxy requires an
extension to the SEND protocol and is left for future work, but is extension to the SEND protocol and is left for future work [SPND],
similar to the problem of securing Router Advertisements which is but is similar to the problem of securing Router Advertisements
supported today. which is supported today. For example, a rogue node can send a
Router Advertisement to cause a proxy to disable its proxy
behavior, and hence cause denial-of-service to other nodes; this
threat is covered in section 4.2.1 of [PSREQ].
Alternative designs might involve schemes where the right for
representing a particular host is delegated to the proxy, or where
multiple nodes can make statements on behalf of one address
[RINGSIG].
10. Appendix A: Comparison with Naive RA Proxy 10. Appendix A: Comparison with Naive RA Proxy
It has been suggested that a simple Router Advertisement (RA) It has been suggested that a simple Router Advertisement (RA)
proxy would be sufficient, where the subnet prefix in an RA is proxy would be sufficient, where the subnet prefix in an RA is
Draft ND Proxy October 2005
"stolen" by the proxy and applied to a downstream link instead of "stolen" by the proxy and applied to a downstream link instead of
an upstream link. Other ND messages are not proxied. an upstream link. Other ND messages are not proxied.
There are many problems with this approach. First, it requires There are many problems with this approach. First, it requires
cooperation from all nodes on the upstream link. No node cooperation from all nodes on the upstream link. No node
(including the router sending the RA) can have an address in the (including the router sending the RA) can have an address in the
subnet or it will not have connectivity with nodes on the subnet or it will not have connectivity with nodes on the
downstream link. This is because when a node on a downstream link downstream link. This is because when a node on a downstream link
tries to do Neighbor Discovery, and the proxy does not send the NS tries to do Neighbor Discovery, and the proxy does not send the NS
on the upstream link, it will never discover the neighbor on the on the upstream link, it will never discover the neighbor on the
upstream link. Similarly, if messages are not proxied during DAD, upstream link. Similarly, if messages are not proxied during DAD,
conflicts can occur. conflicts can occur.
Second, if the proxy assumes that no nodes on the upstream link Second, if the proxy assumes that no nodes on the upstream link
have addresses in the prefix, such a proxy could not be safely have addresses in the prefix, such a proxy could not be safely
deployed without cooperation from the network administrator since deployed without cooperation from the network administrator since
it introduces a requirement that the router itself not have an it introduces a requirement that the router itself not have an
Draft ND Proxy July 2005
address in the prefix. This rules out use in situations where address in the prefix. This rules out use in situations where
bridges and Network Address Translators (NATs) are used today, bridges and Network Address Translators (NATs) are used today,
which is the problem this document is directly addressing. which is the problem this document is directly addressing.
Instead, where a prefix is desired for use on one or more Instead, where a prefix is desired for use on one or more
downstream links in cooperation with the network administrator, downstream links in cooperation with the network administrator,
Prefix Delegation [PD] should be used instead. Prefix Delegation [PD] should be used instead.
11. Authors' Addresses 11. Acknowledgements
The authors wish to thank Jari Arkko for contributing portions of
the Security Considerations text.
12. Authors' Addresses
Dave Thaler Dave Thaler
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
Phone: +1 425 703 8835 Phone: +1 425 703 8835
EMail: dthaler@microsoft.com EMail: dthaler@microsoft.com
Mohit Talwar Mohit Talwar
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
Phone: +1 425 705 3131 Phone: +1 425 705 3131
Draft ND Proxy October 2005
EMail: mohitt@microsoft.com EMail: mohitt@microsoft.com
Chirayu Patel Chirayu Patel
All Play, No Work All Play, No Work
Bangalore, Karnataka 560038 Bangalore, Karnataka 560038
Phone: +91-98452-88078 Phone: +91-98452-88078
EMail: chirayu@chirayu.org EMail: chirayu@chirayu.org
12. Normative References 13. Normative References
[ARP]
D. Plummer, "An Ethernet Address Resolution Protocol", STD
37, RFC 826, November 1982.
[ARPPROXY]
J. Postel, "Multi-LAN address resolution", RFC 925, October
1984.
Draft ND Proxy July 2005
[BRIDGE] [BRIDGE]
T. Jeffree, editor, "Media Access Control (MAC) Bridges", T. Jeffree, editor, "Media Access Control (MAC) Bridges",
ANSI/IEEE Std 802.1D, 2004, ANSI/IEEE Std 802.1D, 2004,
http://standards.ieee.org/getieee802/download/802.1D-2004.pdf. http://standards.ieee.org/getieee802/download/802.1D-2004.pdf.
[DHCPv4]
R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[ICMPv6] [ICMPv6]
Conta, A. and S. Deering, "Internet Control Message Protocol Conta, A. and S. Deering, "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6) (ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", RFC 2463, December 1998. Specification", RFC 2463, December 1998.
[KEYWORDS] [KEYWORDS]
S. Bradner, "Key words for use in RFCs to Indicate S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March, 1997. Requirement Levels", BCP 14, RFC 2119, March, 1997.
[ND] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery [ND] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998. for IP Version 6 (IPv6)", RFC 2461, December 1998.
[NODEREQ] [NODEREQ]
J. Loughney, "IPv6 Node Requirements", Work in progress, J. Loughney, "IPv6 Node Requirements", Work in progress,
draft-ietf-ipv6-node-requirements-11.txt, August 2004. draft-ietf-ipv6-node-requirements-11.txt, August 2004.
13. Informative References 14. Informative References
[6TO4] [6TO4]
Carpenter, B. and K. Moore, "Connection of IPv6 Domains via Carpenter, B. and K. Moore, "Connection of IPv6 Domains via
IPv4 Clouds", RFC 3056, February 2001. IPv4 Clouds", RFC 3056, February 2001.
[DHCPAUTH] Draft ND Proxy October 2005
Droms, R. and W. Arbaugh, Eds., "Autentication for DHCP
Messages", RFC 3118, June 2001. [BCP]
Baker, F. and R. Bowen, "PPP Bridging Control Protocol
(BCP)", RFC 1638, June 1994.
[DHCPv6] [DHCPv6]
Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C. Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C.
Draft ND Proxy July 2005
and M. Carney, "Dynamic Host Configuration Protocol for IPv6 and M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[NAT] [NAT]
Srisuresh, P. and K. Egevang, "Traditional IP Network Address Srisuresh, P. and K. Egevang, "Traditional IP Network Address
Translator (Traditional NAT)", RFC 3022, January 2001. Translator (Traditional NAT)", RFC 3022, January 2001.
[PD] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host [PD] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
Configuration Protocol (DHCP) version 6", RFC 3633, December Configuration Protocol (DHCP) version 6", RFC 3633, December
2003. 2003.
[PSREQ] [PSREQ]
Nikander, P., Kempf, J. and E. Nordmark, "IPv6 Neighbor Nikander, P., Kempf, J. and E. Nordmark, "IPv6 Neighbor
Discovery (ND) Trust Models and Threats", RFC 3756, May 2004. Discovery (ND) Trust Models and Threats", RFC 3756, May 2004.
14. Full Copyright Statement [RINGSIG]
Kempf, J. and C. Gentry, "Secure IPv6 Address Proxying using
Multi-Key Cryptographically Generated Addresses (MCGAs)",
Work in progress, draft-kempf-mobopts-ringsig-ndproxy-02.txt,
August, 2005.
[SEND]
Arkko, J., Ed., Kempf, J., Zill, B. and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[SPND]
Daley, G., "Securing Proxy Neighbour Discovery Problem
Statement", Work in progress, draft-daley-send-spnd-
prob-01.txt, February 2005.
Draft ND Proxy October 2005
15. Full Copyright Statement
Copyright (C) The Internet Society (2005). This document is Copyright (C) The Internet Society (2005). This document is
subject to the rights, licenses and restrictions contained in BCP subject to the rights, licenses and restrictions contained in BCP
78, and except as set forth therein, the authors retain all their 78, and except as set forth therein, the authors retain all their
rights. rights.
This document and the information contained herein are provided on This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. PARTICULAR PURPOSE.
15. Intellectual Property 16. Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology to pertain to the implementation or use of the technology
described in this document or the extent to which any license described in this document or the extent to which any license
under such rights might or might not be available; nor does it under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to rights such rights. Information on the procedures with respect to rights
Draft ND Proxy July 2005
in RFC documents can be found in BCP 78 and BCP 79. in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr. at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to the to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org. IETF at ietf-ipr@ietf.org.
Draft ND Proxy July 2005 Draft ND Proxy October 2005
Table of Contents Table of Contents
1: Introduction ............................................. 2 1: Introduction ............................................. 2
1.1: SCENARIO 1: Wireless upstream .......................... 3 1.1: SCENARIO 1: Wireless upstream .......................... 3
1.2: SCENARIO 2: PPP upstream ............................... 4 1.2: SCENARIO 2: PPP upstream ............................... 4
1.3: Inapplicable Scenarios ................................. 4
2: Terminology .............................................. 4 2: Terminology .............................................. 4
3: Requirements ............................................. 5 3: Requirements ............................................. 5
3.1: Non-requirements ....................................... 6 3.1: Non-requirements ....................................... 6
4: Proxy Behavior ........................................... 7 4: Proxy Behavior ........................................... 6
4.1: Forwarding Packets ..................................... 7 4.1: Forwarding Packets ..................................... 7
4.1.1: Sending Packet Too Big Messages ...................... 8 4.1.1: Sending Packet Too Big Messages ...................... 8
4.1.2: Proxying Packets With Link-Layer Addresses ........... 9 4.1.2: Proxying Packets With Link-Layer Addresses ........... 8
4.1.3: IPv4 ARP Proxying .................................... 9 4.1.3: IPv6 ND Proxying ..................................... 9
4.1.3.1: ARP REQUEST Packets ................................ 9 4.1.3.1: ICMPv6 Neighbor Solicitations ...................... 9
4.1.3.2: ARP REPLY Packets .................................. 9 4.1.3.2: ICMPv6 Neighbor Advertisements ..................... 9
4.1.3.3: DHCPv4 Packets ..................................... 10 4.1.3.3: ICMPv6 Router Advertisements ....................... 9
4.1.4: IPv6 ND Proxying ..................................... 10 4.1.3.4: ICMPv6 Redirects ................................... 10
4.1.4.1: ICMPv6 Neighbor Solicitations ...................... 10 4.2: Originating Packets .................................... 10
4.1.4.2: ICMPv6 Neighbor Advertisements ..................... 10 5: Example .................................................. 11
4.1.4.3: ICMPv6 Router Advertisements ....................... 11 6: Loop Prevention .......................................... 12
4.1.4.4: ICMPv6 Redirects ................................... 11 7: Guidelines to proxy developers ........................... 12
4.2: Originating Packets .................................... 12 8: IANA Considerations ...................................... 13
5: Example .................................................. 12 9: Security Considerations .................................. 13
6: Loop Prevention .......................................... 13 10: Appendix A: Comparison with Naive RA Proxy .............. 14
7: Guidelines to proxy developers ........................... 14 11: Acknowledgements ........................................ 15
8: IANA Considerations ...................................... 14 12: Authors' Addresses ...................................... 15
9: Security Considerations .................................. 14 13: Normative References .................................... 16
10: Appendix A: Comparison with Naive RA Proxy .............. 15 14: Informative References .................................. 16
11: Authors' Addresses ...................................... 16 15: Full Copyright Statement ................................ 18
12: Normative References .................................... 16 16: Intellectual Property ................................... 18
13: Informative References .................................. 17
14: Full Copyright Statement ................................ 18
15: Intellectual Property ................................... 18
 End of changes. 78 change blocks. 
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