On 15-jul-2005, at 3:25, Ned Freed wrote:
>> It would not make much sense, between 2 hosts you can already have >> 65536*65536 possible connections*, which should be more than >> enough(tm) ;) I wonder if there are any hosts actually using more >> than >> 65536 connections at the same time.
> True enough, however, you can only have 65536 connections to a > single service > on a given port.
Sounds like an implementation limitation to me.
Reread my message. It is nothing of the sort.
Demultiplexing should happen on source and destination IP addresses and source and destination port numbers. Assuming the server's IP address and port number are given, that allows for a 65536 sessions towards each possible IP address connected to the network.
This is the limit I'm talking about, which you now have agreed is a protocol design limit and not an implementation limit.
That should be enough, I'd think.
And you'd be wrong. The specific case I've seen is with IMAP4. IMAP4 has the characteristic that you often have a huge number of incoming connections, only a few of which are active at any given time. Designing servers to accomodate huge numbers of connections is a bit tricky, but workable: You typically have to multiplex the connections onto a pool of worker threads rather than having one thread per connection or one thread for all connections. But the key point is that it can be done without exposing the complexity to the people running the system. The 65536 limit, OTOH, has to be dealt with by using multiple server IP addresses, which in turn usually require multiple interfaces and configuration trickery. This slops over to product and even user client configuration, making things more complex and error prone. Mind you, I'm not saying that TCP needs to be redesigned ASAP to allow for a larger number of source ports. IMO the pain would probably outweigh the gain. But that doesn't mean nobody is hitting the 65536 limit imposed by source port numbers. They are, it causes problems, and this needs to be kept in mind. Ned _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf