We have offices in the UK and the US, both with DSL connections. Linux
routers at both ends. We frequently get high packet loss (>10%) and
have had occasional ISP router outages. Yes, we can spend more money
on a leased line, but even so, the transatlantic / continental
carriers on the leased line have had routing problems when the DSL has
been OK. TCP traffic becomes very slow with any appreciable packet
loss - terminal traffic is very slow indeed. End-to-end service
providers cost a fortune - and we don't need very high bandwidth. The
speed of light dictates that we'll always have fairly high latency, so
any retransmissions will be noticeable.
So - it occurs to me that we could use multiple cheap DSLs at both
ends from different telcos/ISPs to guarantee that office-office comms
work. My thought is that something like eql (I'll call it "dup") can
be adapted to duplicate all packets down several links rather than
distributing packets down each link.
UK US
uk-dsl0 --------- us-dsl0
\___ ___/
/ \/ \
uk-dup0 ___/\___ us-dup0
\ / \ /
uk-dsl1 --------- us-dsl1
Every packet into dup0 generates 4 packets out (eth0-eth0, eth0-eth1,
eth1-eth0, eth1-eth1). The exact mechanism isn't the point (I imagine
4 VPNs of some sort, enslaved by dup in the same way as eql) - we just
make multiple packets end up at the destination router somehow.
Q 1: Does mass duplication cause problems to e.g. TCP, which probably
expects a small amount of duplication in the same way that it expects
a small amount of packet loss?
Q 2: Are there any alternative / better (Linux) solutions to provide
this sort of resilience over high latency connections?
Q 3: Has anyone written "dup" ? :-)
--
Peter Lister P.Lister@xxxxxxxxxxx PGP (RSA): 0xE4D85541
Sychron Ltd http://www.sychron.com PGP (DSS): 0xBC1D7258
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