Re: Residential VSAT experiences?

["Fred Baker (fred)" <fred () cisco com>]

> On Jun 22, 2015, at 3:11 PM, William Herrin <bill () herrin us> wrote:
>
> Two-way satellite systems based on SV's in geostationary orbit (like
> the two you're considering) have high latency. 22,000 miles out,
> another 22,000 miles back and do it again for the return packet.
> You'll start around 500ms latency and go up from there. Any kind of
> interactive session (like SSH and RDP) will be excruciating.

It is indeed. This is first-hand in the sense that I once worked for an earth station manufacturer and did a fair bit 
of work related to this environment, and second-hand in that my sister, for a while, used VSAT connectivity to her home.

The trick in the context is what's called a "performance-enhancing proxy", or PEP. What it does, in concept, is 
terminate a TCP connection at each earth station and use some form of private protocol over the bird. Cisco RBSCP 
(which maps TCP connections to SCTP sessions over the bird, 
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/15-sy/ir-15-sy-book/ir-rt-bsd-sat.html) is an 
example of such a technology. The obvious benefit of a PEP is that it can convince a TCP sender to keep enough data in 
flight to make good use of the throughput rate of the satellite - you have a start-up issue with the first RTT, but 
after that it has essentially figured out what the effective window should be and makes that happen. The downside of a 
PEP is when the application is itself interactive (it's not about rate, it's about responsiveness clocked by end-to-end 
RTT) or the protocol in question isn't TCP (noting that TCP in IPsec ESP isn't TCP to the PEP - it's IPsec ESP, and 
can't be goosed along).

In my sister's case, her description of the service was somewhat colorful, and included the word "slow".

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