Subject: RE: WG Action - Accept [LL29] Link-local sources should specify TTL=1

From: "Christian Huitema" <[email-masked]>
Date: Wed, 30 Apr 2003 09:04:57 -0700

> Set TTL 255 and not check doesn't break anything.
> Set TTL 255 and check breaks some implementations, though we've never
> received a report of problems.
> Set TTL 1 breaks some implementations.
> 
> If you're really serious about not breaking any implementations, it
> seems the right thing to do is set the TTL to 255. If you don't care
> about compatibility, then why is setting the TTL to 1 an better than
> 255?

It is very clear that any mandate is going to break something. The
question is very much what the default should be. I believe that using a
TTL 1 makes sense in a lot of cases. It is the right thing to do when
sending UDP multicast. With TCP, the combination of TTL=1 and the three
ways handshake gives you a pretty airtight solution. So it is pretty
clear that if a system wanted to choose TTL=1 by default, they should be
authorized to do so.

-- Christian Huitema

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From: Joshua Graessley <[email-masked]>
Date: Wed, 30 Apr 2003 10:11:48 -0700

On Wednesday, Apr 30, 2003, at 09:04 US/Pacific, Christian Huitema 

> clear that if a system wanted to choose TTL=1 by default, they should 

I'm not sure I follow. How does requiring the TTL be set to 255 and not 
requiring any check break anything?

The only implementations doing any checking are checking for TTL 255. 
If you set the TTL to 255, you will work with those implementations. If 
you check for TTL 255, you will fail to interoperate with 
implementations that don't set the TTL to 255. If you set the TTL to 
anything other than 255, you fail to interoperate with implementations 
that perform the TTL 255 check.

-josh

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From: "Philip Nye" <[email-masked]>
Date: Wed, 30 Apr 2003 20:48:23 +0100

Can anyone here say whether the Apple implementations which set/check
TTL=255 do so for multicast in exactly the same way as for unicast?

Philip

----- Original Message -----
From: "Joshua Graessley" <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, April 30, 2003 6:11 PM
Subject: Re: WG Action - Accept [LL29] Link-local sources should specify
TTL=1