Follow-up to my own e-mail, after some off-line discussions.
Here's an updated suggestion for the address resolution etc part:
2.4 RFC2461 - Neighbor Discovery for IPv6
Neighbor Discovery is described in [RFC-2461]. This
specification is a mandatory part of IPv6.
2.4.1 Neighbor Discovery in 3GPP Networks
Hosts must support Neighbour Solicitation and
Advertisement messages.
In GPRS and UMTS networks, some Neighbor Discovery
messaging can be unnecessary in certain cases.
GPRS and UMTS links resemble a point-to-point link;
hence, the host's only neighbor on the cellular
link is the defaul router that is already known
through Router Discovery. There are no link layer
addresses. Therefore, address resolution and next-hop
determination are not needed.
Secondly, about alternative 1 for the advice to give for NUD.
I've been asked to provide more details about the specific
protocol layers, whether the tunnel and the payload stacks
are the same etc. We'll send an e-mail about this tomorrow.
Finally, for alternative 3 I have some updated text regarding
what kind of advice to give:
The host must support neighbour unreachability
detection as specified in [RFC-2461].
In GPRS and UMTS networks, it is very desireable to
conserve bandwidth. Therefore, hosts stacks used in
these environments should include a mechanism
in upper layer protocols to provide
reachability confirmation when two-way IP layer
reachability can be confirmed (see RFC-2461,
Section 7.3.1). These confirmations will allow the
suppression of most NUD-related messages.
Host TCP implementation should provide
reachability confirmation in the manner
explained in RFC 2461, Section 7.3.1.
The use of UDP for many purposes in 3GPP
networks poses a problem for providing this
reachability confirmation. UDP itself is
unable provide such confirmation. Instead,
applications running over UDP should provide
the confirmation where possible. In particular,
when UDP is used for transporting RTP, the RTCP
protocol feedback should be used as a basis for
the reachability confirmation. If an RTCP
packet is received with a reception report block
indicating some packets have gone through, then packets
are reaching the peer. If they have reached the
peer, they have also reached the neighbour.
When UDP is used for transporting SIP, responses to
SIP requests should be used as the confirmation that
packets sent to the peer are reaching it.
The receipt of new non-retransmitted requests within
a SIP dialog should be used as a confirmation that
previous responses have reached the peer.
Jari
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