Subject: RE: LLMNR and Rendezvous TTL disagreement, a modest proposal

From: Mika Liljeberg <[email-masked]>
Date: Sun, 14 Mar 2004 00:29:16 +0200

Christian,

> Setting the TTL to 1 provides a limited benefit in TCP operation,
> multicast queries and unicast responses, but contradicts the
> requirement of TTL=255 for IPv6 link-local addresses. Setting to
> either value will create operational problems in some future
> scenarios.

This is untrue. IPv6 does not require nor enforce hop limit 255 for
link-local addresses. Only ICMPv6 neighbor discovery packets use hop
limit 255. This is not a constraint for LLMNR.

> The simplest solution is probably to remove all mentions of TTL checks
> from the LLMNR document, and simply state that:
> 1) Nodes should verify that the source address of queries belong to an
> authorized range;

This seems useful.

> 2) The TTL field should be set by the stack to whatever default value
> is adequate for the interface and the source address (e.g., TTL=255
> for IPv6 link-local addresses.)

Ok, although I would rather suggest:

2) Use TTL=1 with TCP.

3) No TTL requirements for UDP requests and responses, but recommend
setting to 255 for compatibility with Rendezvous.

	MikaL

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From: Joshua Graessley <[email-masked]>
Date: Mon, 15 Mar 2004 10:30:45 -0800

Works for me.

-josh

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From: Mika Liljeberg <[email-masked]>
Date: Sun, 14 Mar 2004 00:29:16 +0200

Christian,

This seems useful.

2) Use TTL=1 with TCP.

	MikaL

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From: Joshua Graessley <[email-masked]>
Date: Mon, 15 Mar 2004 10:30:45 -0800

Works for me.

-josh