Re: [Int-area] 答复: 答复: 答复: 答复: Is the UDP destination port number resource running out?// re: I-D Action: draft-ietf-intarea-gue-04.txt

Joe Touch <touch@isi.edu> Thu, 25 May 2017 19:14 UTC

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From: Joe Touch <touch@isi.edu>
To: Tom Herbert <tom@herbertland.com>
Cc: Xuxiaohu <xuxiaohu@huawei.com>, "int-area@ietf.org" <int-area@ietf.org>
References: <149514799195.6631.3231700013200014494@ietfa.amsl.com> <CALx6S37nrJNGLdRHWx9DYNQyS54YdwLCXcG9Mp3zi4L_wrr6=g@mail.gmail.com> <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE2BBA8877@NKGEML515-MBX.china.huawei.com> <a3915b87-f104-51d8-11e3-d9f8196462b5@isi.edu> <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE2BBA8903@NKGEML515-MBX.china.huawei.com> <54980b3a-2dc9-2ab1-f150-45b3f500f7ac@isi.edu> <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE2BBA892E@NKGEML515-MBX.china.huawei.com> <CALx6S350VcJCm4g70jycbXD3FxaGg9eF-dn61_SdVF8xmmkojg@mail.gmail.com> <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE2BBA95EA@NKGEML515-MBX.china.huawei.com> <CALx6S34dQX8gGCLvR4OG70FfO7MY8CbOxB_CA-crcTmFE_zX3g@mail.gmail.com> <d1c22f64-1cab-2946-32a6-4339a197402e@isi.edu> <CALx6S365N44zV=-N3BgA9ATibfqW5G78_4cDD4EnL1muDoA04Q@mail.gmail.com> <7b56cfb4-87a9-a3c0-98ab-19acfed01da5@isi.edu> <CALx6S37SQivoYNsPnQOCvG2UpNk=_7rThD5rQP3gPmwqx+1siA@mail.gmail.com> <85610864-3b00-67b3-6d3a-db1c4ef3870b@isi.edu>
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Date: Thu, 25 May 2017 12:13:54 -0700
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FWIW, my general concern with this service is that lacks a version
identifier, and cannot be extended to support such an identifier for
bare IP packets as payloads, as encouraged by RFC7605 Section 7.5

At a minimum, one of the first fields after the "Version 0" format
identifier (a name which is confusing, for this reason) needs to be a
version field, so that future variants of this service will not need a
new port assignment.

Joe


On 5/25/2017 12:07 PM, Joe Touch wrote:
>
>
>
> On 5/25/2017 11:47 AM, Tom Herbert wrote:
>>> You can't put bare Ethernet inside GUE. You need to use EtherIP -
>>> exactly because it has a 16-bit field, of which only the first 4 bits
>>> are (already) defined.
>>>
>>> My point is that EtherIP burns 16 bits vs bare Ethernet, but those 16
>>> bits allow it to be mapped to one of the IP versions (you picked IPv5).
>>> The same trick works for UDP and TCP - just pick a different 16 bit
>>> pattern for each one.
>>>
>> Inserting two bytes before the TCP header breaks four byte alignment
>> of the header which is a bigger hit than the benefit of saving two
>> bytes. A nice side effect of the two byte header in EtherIP is that it
>> aligns the Ethernet payload (e.g. an IP header) to four bytes.
>> Maintaining this four byte alignment is still important to some CPU
>> architectures most notably Sparc, but can even be problematic to x86
>> under certain circumstances.
>>
>> Tom
> Sure - I'm not sure the 4-byte penalty is worth avoiding any nearly
> any case, frankly -- even for IP.
>
> Joe