Subject: WG Action - 1 week to discuss [LL29] Link-local sources should specify TTL=1

From: Erik Guttman <[email-masked]>
Date: Thu, 27 Feb 2003 19:20:53 +0100 (CET)

The following issue is an alternative to LL3 and LL21.  Please discuss
this over the following week, ending March 6.  We will make a consensus
decision at that point between accepting issue LL3, LL21 or LL29.

Please also see http://www.spybeam.org/ll29.html

Description of issue: Link-local sources should specify TTL=1
Submitter name: John Schnizlein
Submitter email address: [email-masked]
Date first submitted: 2003-02-27
Comment type: ['T'echnical | 'E'ditorial] T
Priority: ['S' Must fix | '1' Should fix | '2' May fix ] S
Section: 2.7
Rationale/Explanation of issue: Alternative to LL3 and LL21
Proposal:

Replace the current contents of section 2.7 with the following:

   Any host sending an IPv4 packet with a source and/or destination
   address in the 169.254/16 prefix MUST set the TTL in the IP header
   to 1. This includes multicast and broadcast packets with a source
   address in the 169.254/16 prefix."
   
   This requirement enables the normal behavior of Internet routers
   to preclude leaking traffic that is supposed to be confined to a
   single link out into the Internet when the local link has an
   attachment to the Internet that it did not discover. Setting TTL
   to 1 precludes mistaken forwarding of link-local traffic even
   when proxy-ARP is used on a link.

Lengthy description of problem: see discussion of LL3 and LL21

---

From: John Schnizlein <[email-masked]>
Date: Thu, 27 Feb 2003 15:28:48 -0500

This is a good suggestion. It might also provide for interoperability, 
for example, where a Windows LL host wants to mount an AppleShare
file-store, it could use the TTL in legacy Macintosh implementations.

The default value protects the Internet; applications that want to
can accommodate the historical choices of pre-standard values.

John

At 03:00 PM 2/27/2003, Christian Huitema wrote:
>.... I would suggest accepting LL29, but rewriting it as:
>
>  address in the 169.254/16 prefix SHOULD set the TTL in the IP 
>  header to 1, unless another value is specifically requested by the
>  application. This includes multicast and broadcast packets with a
>  source address in the 169.254/16 prefix."