2010/3/19 Jim Thomas <jimthomasembed...@yahoo.com>: > The DNS server is provisioned to rotate the SRV records > round-robin, so the first choice will alternate among the three > destinations. I can see in a packet trace that the SRV record > sequence is in fact alternating across DNS lookups. (These are > the external DNS lookups after the Sofia-SIP DNS cache expires). > The problem is that even though the DNS response presents the > SRV records in varying order, Sofia-SIP always selects the same > particular SRV record, so outbound calls always go to a single > destination and are not distributed. ... > The result is that Sofia-SIP loses the SRV record sequence intended > by the round-robin ordering by the DNS server, and the SRV record > selected by Sofia-SIP is always the record that just happens to have > the target name with the lowest alpha sort key.
Sofia SIP is supposed to select SRV record randomly. However there is a problem with SRV records with zero weight. If all the SRV records have zero weight, the first one after the sort is always selected. A far as I can remember, this is because the weight 0 is used to indicate that no server selection is done. If the weights are greater than 0, the server selection should be pretty random. > It seems to me that the correct sort would be by priority and weight > only, and where those are identical for adjacent records, the original > SRV record sequence would be preserved so the first choice intended > by the DNS server round-robin ordering would be used by Sofia-SIP > to determine where to send the SIP for the outbound call. You are right, the sorting tries now support stateless proxies, the nta should probably not use the default sorting algorithm but do its own or do some special randomization in case of 0 weights. -- Pekka.Pessi mail at nokia.com ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Sofia-sip-devel mailing list Sofia-sip-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sofia-sip-devel
