| > | Do we calculate mss anywhere? | > Yes there is support in dccps_mss_cache . | > At the begin of dccp_send_msg e.g. it is used. | | Yup, look at dccp_sync_mss() used in dccp_connect_init(): <snip> Thank you for the helpful `pointers' :) - I was amazed a couple of months ago about how much of that code is active and quietly doing its job with accuracy. | /* | * FIXME: this should come from the CCID infrastructure, where, | * say, TFRC will say it wants TIMESTAMPS, ELAPSED time, etc, | * for now lets put a rough estimate for NDP + TIMESTAMP + | * TIMESTAMP_ECHO + ELAPSED TIME + TFRC_OPT_LOSS_EVENT_RATE + | * TFRC_OPT_RECEIVE_RATE + padding to | * make it a multiple of 4 | */ | | mss_now -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4; | I thought that when we are actively using the provided MSS facilities, then there is more incentive to tackle this one above too. | Infrastructure wise I guess struct ccid_operations should have a... | lemme read the relevant part of 4340... there CCMPS: | | ----------------- 8< ------------- | 14. Maximum Packet Size | | A DCCP implementation MUST maintain the maximum packet size (MPS) | allowed for each active DCCP session. The MPS is influenced by the | maximum packet size allowed by the current congestion control | mechanism (CCMPS), the maximum packet size supported by the path's | links (PMTU, the Path Maximum Transmission Unit) [RFC1191], and the | lengths of the IP and DCCP headers. | ----------------- 8< ------------- I don't know how often I read through 4340, 4341 and 4342 trying to find out what `CCMPS' is for - it seems that in CCID2 and CCID3 it is both set to `infinity', at least I can find no explicit mention in 4341/4342 of CCMPS. But for the MSS caching a `ccid_mps' member would be useful anyway for the above required purpose. This in turn re-opens other questions - in CCID3 e.g. feedback packets should always contain also a Loss Intervals option - which is still missing in CCID 3. It is good that you raise this; I put a copy into my ToDo folder and will ask around in some time if anyone is working on it. If no one else does it I will give it a try at some time, but am bogged down by other work. I am re-working the CCID `larger initial windows' patch at the moment, plus sequence number issues. - To unsubscribe from this list: send the line "unsubscribe dccp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
