[Int-area] Re: [EXTERNAL] Re: [tsvwg] UDP options [was IP Parcels and Advanced Jumbos (AJs)]

Hi Joe, see annotations below:

Thank you - Fred

From: [email protected] <[email protected]>
Sent: Monday, September 30, 2024 8:30 AM
To: Templin (US), Fred L <[email protected]>
Cc: C. M. Heard <[email protected]>; Brian Carpenter <[email protected]>; Gorry (erg) <[email protected]>; Tim Chown <[email protected]>; Internet Area <[email protected]>; IPv6 List <[email protected]>; tsvwg IETF list <[email protected]>
Subject: [EXTERNAL] Re: [tsvwg] UDP options [was IP Parcels and Advanced Jumbos (AJs)]

On Sep 30, 2024, at 8:08 AM, Templin (US), Fred L <[email protected]<mailto:[email protected]>> wrote:

> Please review the UDP options doc. There is no “end *following* UDP options”; the options consume the entire surplus space.

Yes, so IP parcels and AJs will update the base UDP options spec. For IP parcels and AJs, a 2-octet trailer can
then be added beyond the end of the UDP options space.

In UDP options for <64K, the IP length field indicates the end of the options space. The UDP length indicates the payload. UDP options consume the difference between the two.



>> Yes, the same is true for parcels/AJs < 64K, except that the overall length appears in the Parcel Payload Length

>> of the HBH option  instead of in the IP length field. The same as for ordinary packets, though, the UDP length

>> indicates the end of the payload and the beginning of the options. The difference between these two lengths

>> also gives the length of the included options.

For parcels, where is that information as distinct from those to items?

Further, there are numerous other places where UDP options assume a 64KB limit (e.g., FRAG).

All that would need to be worked out in detail to consider whether the two could co-exist,  if and when we think we actually need support for beyond 64K.

>> For parcels/AJs >= 64K, the overall length appears in the Parcel Payload Length of the HBH option and
>> the UDP length is set to 0. The IP parcels draft specifies that UDP Length = 0 means that there will be
>> a trailing 2-octet UDP Option Length field beyond the end of what would be considered the UDP options.
>> The trailing field is not part of the UDP options, but is used to determine the starting offset and length
>> of the UDP options. Again, this is only for parcels/AJs >= 64K.

Joe

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