As part of the NWAM project, we are investigating the support
of IPv4 LLA in Solaris. One big issue with IPv4 LLA support
is the multi-homing nature of most Solaris machine. In fact,
RFC 3927 is not clear exactly how LLA works in this case. The
problem is simple, LLA is not unique. And if a system has
multiple IP interfaces all using LLAs and an app wants to talk
to a peer with a LLA, on which interface should the system
"find" the peer? And what happens if there is a host using
that LLA in each links of those interfaces? Note that unlike
IPv6 apps, most IPv4 apps do not really care about which
interface is being used for communication, as it should not
matter mostly (LLA is a "new" concept).
To make the issue more complicated, the RFC mentions that a
system supporting LLA but with routable address should be able
to communicate with another system using LLA if both systems
have interfaces on the same "link." This means that LLA capable
systems can talk to each other using either routable address or
LLA. The following is a simple case,
A1 +--------+ A2 OOOOOOO B2 +--------+ B1
-----+ Host A +-------O Net X O--------+ Host B +-----
+--------+ OOOOOOO +--------+
A1, B1 and B2 are routable addresses and A2 is LLA. The
RFC requires that an app in B can talk to an app in A using
A2. So somehow B can find out which interface to use in order
to talk to A2, which is B2. Another interesting part is that
since B2 is routable, when an app in A wants to talk to B2,
the communication should "normally" be done via A1, not A2.
IPv6 used to have a "similar" behavior as the above, the on-link
assumption. But it was thought to be bad and has been removed.
Here are some questions.
1. Is LLA support essential to Solaris networking that we need
to include it and make it work?
2. If we really need to support it, is it OK for it to "work
in some cases but not all?" The RFC does not have a solution
to make it work with multiple interfaces.
3. Is it OK to have certain limitations, such as only supporting
LLA in one interface? Or not support the communication
between LLA and routable address? Or ... This is to allow
us to have a more "consistent" failure mode.
Comments and suggestions?
--
K. Poon.
[EMAIL PROTECTED]
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