Re: [dccp] UDP encaps for SCTP and SCCP

[Eddie Kohler <[e-mail]>]

Hi Lars,

I vote for (1), SCTP-specific and DCCP-specific UDP encaps.

Although those specific encaps could be very similar, or in fact 
identical at first, there are enough protocol differences to recommend 
planning ahead for potential divergence.

At minimum there could be two documents that allocate different 
well-known UDP ports for SCTP-in-IP-in-UDP encapsulation and 
DCCP-in-IP-in-UDP encapsulation (which if I understand correctly is the 
"simple UDP tunnel" Lloyd prefers).  I would prefer this to GUT, which 
chooses to expend header space rather than port space.

FWIW, my preferred form of tunneling for DCCP would be DCCP-in-UDP 
encapsulation.  The DCCP header would be unchanged, except for the 
pseudoheader used for checksumming.  This pseudoheader would have source 
and destination addresses all zero; the padded IP protocol number for 
DCCP; and the padded DCCP length.  I believe this would suffice to pass 
current NAPTs, which won't modify the encapsulated DCCP ports.  The UDP 
header checksum could be 0 or not; if nonzero, the DCCP checksum could I 
suppose be ignored, but I don't feel strongly.  UDP-Lite could be used 
or not; I would hope the port number would be the same either way.

Eddie



On 5/18/10 12:37 AM, Lars Eggert wrote:
> Hi,
>
> the discussion has touched on lots of things related to UDP encaps, but I haven't seen anything I'd call consensus on the question below. I'd therefore like to ask folks to specifically state which option they support:
>
> (1) do one SCTP-specific and one DCCP-specific UDP encaps
> (2) do one generic UDP encaps that can be used with both
> (3) do neither (don't do any sort of UDP encaps for SCTP and DCCP)
>
> Thanks,
> Lars
>
> On 2010-4-22, at 12:57, Eggert Lars (Nokia-NRC/Espoo) wrote:
>> Hi,
>>
>> as most of you probably know, there are two different proposals for how to encapsulate SCTP and DCCP inside UDP.
>>
>> One approach proposes two protocol-specific encapsulation schemes (described in draft-tuexen-sctp-udp-encaps and draft-ietf-dccp-udpencap).
>>
>> The second approach proposes a generic encapsulation scheme that can be applied to both SCTP and DCCP (draft-manner-tsvwg-gut).
>>
>> As a community, we do need to come to consensus on which of these two approaches we want to follow when it comes to UDP encapsulation of SCTP and DCCP. I believe it would be very confusing if we were to standardize both approaches.
>>
>> I'd hence like to ask folks to read the three documents and post their views to the [e-mail] list. I'm personally especially interested in hearing from folks who aren't on the author lists of the documents, but obviously, the authors expert opinions do matter.
>>
>> Thanks,
>> Lars
>>
>> PS: I'm pushing on this topic, because UDP encapsulation is the last remaining work item in the DCCP working group before it can close...
>