It might be worth looking at whether the servers support multiple queries over one connection, and whether they support pipelining, and what - if any - difference that makes. A 2nd, and any subsequent, query on a TCP connection won't incur the cost of a handshake, and if pipelining is handled correctly - using Nagling, or TCP_CORK/TCP_NOPUSH, then responses can co-habit TCP packets. I can tell from real-world metrics that at least some resolvers do support, and actually make, multiple requests over the same TCP connection - though they are rare. On Wed, Oct 17, 2012 at 1:49 AM, Anand Buddhdev <anandb@ripe.net> wrote:
[Apologies for duplicates]
Dear colleagues,
The RIPE NCC has just published an article on RIPE Labs, comparing the TCP and UDP response times of DNS queries to the root name servers:
https://labs.ripe.net/Members/bwijnen/tcp-udp-dns-soa-rt-ratio
Your comments, questions and suggestions are welcome.
Regards,
Anand Buddhdev RIPE NCC
-- Colm