Re: [shim6] How long is a shim6 header?

Brian E Carpenter <brian.e.carpenter@gmail.com> Sat, 02 November 2013 14:39 UTC

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Date: Sun, 03 Nov 2013 03:39:06 +1300
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Cc: shim6@ietf.org
Subject: Re: [shim6] How long is a shim6 header?
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Sure, I agree about 8 minimum: my suggestion was that 40 was a typical
*large* header.

1280 would be a complete disaster since firewalls will *never* be able
to deal with that at line speed. Please read draft-wkumari-long-headers-02
to understand the concern. We missed this issue during the shim6 design,
I think.

Regards
   Brian

On 02/11/2013 21:22, Sébastien Barré wrote:
> Hi,
> 
> the biggest extension headers are found in signalling packets, in
> particular those that carry locator information.
> Since any number of locators can be advertised to the peer, the Shim6
> signalling packet may grow up to 1280 bytes, the maximum allowed for
> shim6 (ref: rfc5533, section 5.1), including
> the IPv6 header. This leaves up to 1240 bytes for the Shim6 header.
> 
> Now, this is for signalling. If you worry about payload packets only,
> then the Shim6 header is either simply absent (when ULIDs are used, the
> shim6 context at the receiver is looked up based on them), or it
> contains only a context tag and its size is then 8 bytes. (rfc5533,
> section 5.2)
> 
> So, unless I miss something, the Shim6 minimum header size is 8 bytes,
> not 40.
> 
> Hope this helps,
> 
> Sébastien.
>>
>> -------- Original Message --------
>> Subject: [shim6] How long is a shim6 header?
>> Date: Wed, 30 Oct 2013 07:53:41 +1300
>> From: Brian E Carpenter <brian.e.carpenter@gmail.com>;
>> Organisation: University of Auckland
>> To: shim6-wg <shim6@ietf.org>;
>>
>> Hi,
>>
>> Does anyone have a quick answer to this question: how big is the
>> biggest SHIM6 extension header that is likely to occur in practice?
>>
>> As far as I can see, it's at least 40 bytes.
>>
>> The context for this question is draft-wkumari-long-headers.
>>
>> Regards
>>    Brian Carpenter
>>
>> _______________________________________________
>> shim6 mailing list
>> shim6@ietf.org
>> https://www.ietf.org/mailman/listinfo/shim6
>>
>>
>>
> 
>