RE: Protocol and port fields in selectors

[sakari.poussa@nokia.com]

sakari.poussa@nokia.com wrote:
>> In 3G/IMS SIP case, the mobile phone binds to the same local port
>> for TCP and UDP. For the remote ports, the SIP uses 5060 for
>> both TCP and UDP. So in this case, the local&remote ports 
>> are the same for both protocols, and that's why there is
>> temptation to use wildcard for the protocol field. 
>> 
>> So it would work for this application, and may not be literally
>> according to the spec., but why do you think it is dangerous?
>
Joe Touch wrote:
>What happens if/when those ports are used by a new transport protocol, 
>e.g, for an application of which you are not aware?

You are rigth, it does not work. The assumption is that the 
same ports will be used for the new transport protocol.

>>>At best, though, it seems like this cuts the database down 
>by a factor 
>>>of 2; is there that much utility to such an optimization?
>> 
>> That is actually the whole idea; to reduce the number of SAs. Since
>> we are talking about several hundred thousands of SAs, 
>cutting the size
>> in half reduces the memory requirements (a lot) and improves 
>performance.
>
>That's purely an implementation detail. It seems sufficient in 
>this case 
>to implement it as an extra bit that says "TCP and UDP", 
>rather than to 
>leave it as a completely open wildcard.

Yes, I'll buy that one! I was actually thinking it myself, but 
the selector fields (in general) do not have this kind of AND/OR
capabilties. But one can easily add that.

>Joe

-sakari