Re: Split flows across Domains

[Matt Buford]

On Tue, 24 Jan 2006, Christopher L. Morrow wrote:

> that was my thought... and yes, it could get ugly for tcp services. Why
> would you knowningly induce this complication?
When you want single flows to go faster than a single member link? (not that 
I am saying this is a good idea)

Actually, TCP handles out of order packets rather well as long as the 
reordering isn't too severe.  You see a bunch of SACKs flying around, but as 
long as it doesn't get too out of hand it doesn't affect throughput.

It is the non-TCP protocols that often suffer.  Many of them implement 
sequence numbers and simply drop out of order packets.  From my own 
experience, RealPlayer UDP streams and PPTP are two examples that fail (or 
at least feel like 50% packetloss) under heavy reodering, where TCP 
continues to work reasonably well.

Years ago, I had ISDN and IDSL between home and the ISP I worked at, and out 
of curiosity I experimented with per-packet load balancing across these 
links.  Reordering was rather severe, as these links had slow uneven speeds, 
and uneven latencies.  TCP transfers got about 192kbit (75% total link 
capacity, 1.5 times single link capacity), but things like RealPlayer and 
PPTP VPNs were downright unusable.