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Re: [tsvwg] RDMA Support by UDP FRAG Option

Tom Herbert <tom@herbertland.com> Sat, 19 June 2021 18:10 UTC

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From: Tom Herbert <tom@herbertland.com>
Date: Sat, 19 Jun 2021 11:09:45 -0700
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To: "C. M. Heard" <heard@pobox.com>
Cc: Gorry Fairhurst <gorry@erg.abdn.ac.uk>, Joseph Touch <touch@strayalpha.com>, TSVWG <tsvwg@ietf.org>
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Subject: Re: [tsvwg] RDMA Support by UDP FRAG Option
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On Sat, Jun 19, 2021 at 11:01 AM C. M. Heard <heard@pobox.com> wrote:
>
> On Sat, Jun 19, 2021 at 10:11 AM Tom Herbert wrote:
>>
>> There is another serious problem with transport checksums and use of
>> the UDP surplus area. Most of this discussion has presumed that the
>> UDP checksum is the one in the packet being offloaded, but that may
>> not be the case. Consider the case where a sender sends a TCP packet
>> that is encapsulated GRE/UDP or VXLAN (a very common use case in
>> virtual networks where VMs send packets on their virtual networks).
>
>
> Is there a use case for employing UDP options with GRE/UDP? Or GUE?
>
Mike,

We can divide UDP encapsulations into two flavors. Those that are
extensible and contain their own TLVs or equivalent method to encode
ancillary data, and those that don't have that. GUE and Geneve are
examples of UDP encapsulation protocols that have their own
extensibility mechanisms and hence wouldn't be used with UDP options,
GRE/UDP and VXLAN don't have extensibility so UDP options could be
useful with those protocols.

Tom

> Mike Heard

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