|[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]|
On 7 Apr 2010, at 19:02, Pasi Sarolahti wrote:
On Apr 7, 2010, at 7:26 AM, Phelan, Tom wrote:[Tom P.] The purpose of short sequence numbers in DCCP-STD is to reduceHave the benefits vs. disadvantages of defining a different DCCP header for UDP encapsulation been discussed earlier? The current method saves some redundant header space, but may add to implementation complexity in the DCCP side. I can't say if this is a significant concern, but I wonder if it is a problem that DCCP-UDP supports different set of features than native DCCP, such as not supporting the short sequence numbers?header length. Supporting short sequence numbers in DCCP-UDP doesn't reduce the header size. The purpose of long sequence numbers in DCCP-STD is to reduce the probability of a blind attacker correctly guessing the sequence numbers in use.So in my view short sequence numbers are more of a bug than a feature,and not supporting them in DCCP-UDP is the better solution.Ok, this is fair reasoning. But still, as a matter of design principle, I think it is a little unusual that when receiving a packet for a protocol, the receiver would need to consider what was the previous header in order to parse the current protocol header. Ideally one might want to use the same DCCP implementation regardless of whether the packets go inside IP or UDP. But I'd be interested to hear what others think.
Agreed. The fewer changes that are required to run DCCP over UDP than over IP, the better. I'd greatly prefer the DCCP header to be identical in both cases, since it simplifies implementations.
-- Colin Perkins http://csperkins.org/