A lot of times, bad MTU settings are the problem with a sat link. The problem is simply stated: GRE tunnels are common on such links, and a GRE tunnel will encapsulate each packet and add a 16 byte header. Since the modems usually only permit a 1500 byte MTU, this means the maximum packet size you can get through the GRE tunnel will be 1484 bytes long, inclusive of header. If someone sends out a packet that is maximum size for a 1500 byte MTU, and sets the DF (Don't Fragment) bit, when the packet hits this GRE tunnel it will be dropped. This happens frequently with bad SSL implementations.
This is only one version of MTU problems with sat links. There are others.
The problem with a satellite connection is not precisely related to latency but rather to jitter, the large differences in latency from one packet to the next. This happens as a result of rain fade, or a poorly engineered link to your transponder on the bird, or a variety of other more infrequent issues.
You can (and should) up your TCP timeout values from the default 3 seconds on a satellite connection, and adjust the http keep-alive timeout, etc, but a lot of times this just means you wait longer to be told when the connection fails.
The solution is a combination of caching, compression, and a performance enhancing proxy or PEP. The PEP does TCP spoofing, basically faking the acknowledgements to speed up the transmission of packets. Compression is similar to the MNP5/v.42bis stuff from modem days applied to a satellite connection. Caching is basically Squid. A lot of PEPs combine all three functions into one - Riverbed is a really good example, though i've worked with pretty much every vendor and they all do the same stuff, with differences in ease of use and efficency.
Implement the timeout fixes, implement a good PEP with all three of the ingredients noted, and make sure the connection is dialed in well with a good shot (line of sight) without physical impediments like trees, buildings, and most importantly microwave interference, and you should have a fairly reliable internet connection. You will still take hits, but you can look at the front of the satellite modem and see that is happening if it's an iDirect or something similar.
Bottom line though is that unless you are taking hits, you should be able to set up downloads of a lot of images and never see a timeout.
- someone who has spent a lot of time doing this (and living off sat connections) in awful places in the world
Maybe, 'except, you're not surviving Venereal weather?'
I seem to recall that we only use 'Venusian' because 'Venereal' was already taken by the medical community.....
Not really, but I do make a point to listen to new episodes of the Adam Ruins Everything podcast; I enjoy the show, and the podcasts are usually interesting as all hell.
Also, Freakonomics Radio.
I am here by the will of the people and I won't leave until I get my raincoat back. - a slogan of the anarchists in Richard Kadrey's "Metrophage"