Transcript Forwarding IPv6 Multicast Messages on Link-layer

Forwarding IPv6 Multicast Messages on Link-layer
Sri Gundavelli
Mark Townsley
Ole Troan
Wojciech Dec
draft-gundavelli-v6ops-l2-unicast
IETF 77:: v6ops:
Unicast Transmission of Multicast Messages on Link-layer
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Motivation

When transmitting an IPv6 packet to a layer-3 multicast
group address, the destination address in the link-layer
header is typically set to the corresponding mapped
address of that multicast group address.
Destination Address
in the Layer-3 Header
Destination Address
in the Layer-3 Header

It is not always desired that the destination address in the
link-layer header is a mapped multicast equivalent of its IP
destination address. There are various deployment
scenarios where there a need to transmit an IPv6
multicast message as an unicast message on the linklayer.

Such a message construct is used in various protocols,
such as in ISATAP [RFC5214] for sending a unicast
Router Advertisement message on ISTAP interfaces.
IETF 77:: v6ops:
Unicast Transmission of Multicast Messages on Link-layer
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Motivation (Contd ...)

For example, an 802.11 wireless access point may be
hosting multiple IPv6 subnets and it would need the ability
to selectively advertise hosted IPv6 prefixes on a per-node
basis. Such segregation can only be possible by sending
RA’s in unicast mode.

The base IPv6 specifications, such as [RFC4861], or
[RFC2464] do not make any assumption on such tight
relationship and it does not require the receiving IPv6
node to explicitly apply any such checks.

The function of the link-layer is purely for transmitting the
frame to a peer or to a set of peers on a given media. It is
inconsequential for the network layer protocols to go
across the layers and check the semantics of message
delivery in the link-layer header. Any such check is a
violation of the principles of protocol layering and does not
serve any purpose.
IETF 77:: v6ops:
Unicast Transmission of Multicast Messages on Link-layer
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Proposal
 This document proposes that we clearly allow this mode
of transmission by adding an explicit note.
IETF 77:: v6ops:
Unicast Transmission of Multicast Messages on Link-layer
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Thank You
IETF 77:: v6ops:
Unicast Transmission of Multicast Messages on Link-layer
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