Re: [Softwires] Objection to 4rd-U made in Softwire meeting understood to be invalid

Rémi Després <> Wed, 16 November 2011 05:42 UTC

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From: Rémi Després <>
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Date: Wed, 16 Nov 2011 13:42:47 +0800
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Subject: Re: [Softwires] Objection to 4rd-U made in Softwire meeting understood to be invalid
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Le 16 nov. 2011 à 10:26, Ole Troan a écrit :

> Remi, et al,
>> In the Softwire meeting of Monday, the key argument against the 4rd unified approach (4rd-U) was that *Because checksum neutrality of addresses is part of 4rd-U, it would allegedly cause "address spreading" (addresses used between a pair of hosts would vary)*. 
>> You had a slide asserting it, and the argument was taken as granted, and important, in verbal comments from Mark Townsley and Dave Thaler.
>> I forcefully declared that this was technically false.
>> Since no time has been granted to explain, I invited anyone in doubt to contact me for explanations. 
>> Thanks for having taken the time to do it.
>> Following our discussion of yesterday, I think you now understand that, as I said:
>> - *TCP/UDP checksum neutrality of addresses DOES NOT interfere in any way with stability of addresses between host pairs*.
> acknowledged. as far as I can understand the checksum neutrality proposal will work, and it will result in stable addresses.
> two flows between two hosts will have the same addresses. and there is no "destination spread" with this mechanism.
> apologies for the uncertainty and confusion created by questioning this.

No problem left on this.

>> - Consequently, the key argument of the meeting against 4rd-U is invalid.
> that I disagree with. there were multiple arguments.

No contradiction here either: I just wished it to be known by the group that the "key" objection is now understood to be invalid.
I do agree that other objections you list in your email, despite their being much less decisive AFAIK, deserve to be seriously discussed. I will comment them in a separate response.