Re: [v6ops] draft-ietf-v6ops-pmtud-ecmp-problem WGLC

joel jaeggli <joelja@bogus.com> Wed, 10 June 2015 05:44 UTC

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To: Mark ZZZ Smith <markzzzsmith@yahoo.com.au>, Brian E Carpenter <brian.e.carpenter@gmail.com>, "v6ops@ietf.org" <v6ops@ietf.org>
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From: joel jaeggli <joelja@bogus.com>
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Subject: Re: [v6ops] draft-ietf-v6ops-pmtud-ecmp-problem WGLC
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On 6/9/15 3:09 AM, Mark ZZZ Smith wrote:
> 
> 
> 
> 
> ________________________________
> From: joel jaeggli <joelja@bogus.com>
> To: Brian E Carpenter <brian.e.carpenter@gmail.com>om>; v6ops@ietf.org 
> Sent: Monday, 8 June 2015, 5:02
> Subject: Re: [v6ops] draft-ietf-v6ops-pmtud-ecmp-problem WGLC
> 
> 
> On 5/31/15 4:45 PM, Brian E Carpenter wrote:
>> Hi,
>>
>> Generally I think this is useful and almost ready.
>>
>>> 3.1.  Alternatives
>>>
>>>    As an alternative, it may be appropriate to lower the TCP MSS to 1220
>>>    in order to accommodate 1280 byte MTU.  We consider this undesirable
>>>    as hosts may not be able to independently set TCP MSS by address-
>>>    family thereby impacting IPv4, or alternatively that it relies on a
>>>    middle-box to clamp the MSS independently from the end-systems.
>>
>> The "that" in the second sentence doesn't parse. I don't understand
>> what the draft is trying to say about MSS clamping.
> 
> Is this better?
> 
> or alternatively that middle-boxes need to be employed to clamp the MSS
> 
> independently from the end-systems.
> 
> / I think it is also necessary to point out that the 1220 MSS value doesn't allow for any EHs if the packet size is limited / being limited to 1280. Middle boxes should also be taking into account the present EHs if they adjust the TCP MSS.

It's worth noting i suppose, as a potential contributor to mtu size
issues I think we can do that. if you send extension header containing
packets or fragments to my servers, pmtud is maybe isn't the biggest
problem because they'll never arrive.  :/

>> Also, shouldn't we say "undesirable but possibly necessary in some
>> cases"? A server at the mercy of an ISP might *need* to apply MSS clamping.
> 
> since we are dealing with alternative mitigations we are justifying why
> we don't like them, I thin they can be employed.
> 
>> Nit:
>>
>> It's confusing to have these two sections with identical titles:
>>
>>> 3.1.  Alternatives
>>> 3.2.1.  Alternatives
>>
>> Maybe 3.1 should be "MSS-based Alternatives"
>> and 3.2.1 "Distributed Proxy Alternatives"
> 
> nice.
> 
> thanks
> 
> 
> 
> 
>>    Brian
>> On 01/06/2015 06:00, fred@cisco.com wrote:
>>> This is to initiate a two week working group last call of
>>> http://tools.ietf.org/html/draft-ietf-v6ops-pmtud-ecmp-problem. 
>>> Please read it now. If you find nits (spelling errors, minor suggested
>>> wording changes, etc), comment to the authors; if you find greater
>>> issues, such as disagreeing with a statement or finding additional
>>> issues that need to be addressed, please post your comments to the
>>> list.
>>>
>>> We are looking specifically for comments on the importance of the
>>> document as well as its content. If you have read the document and
>>> believe it to be of operational utility, that is also an important
>>> comment to make.
>>>
>>> _______________________________________________
>>> v6ops mailing list
>>> v6ops@ietf.org
>>> https://www.ietf.org/mailman/listinfo/v6ops
>>>
>>
>> _______________________________________________
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> 
> 
> 
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