Bi-Directional IP Over Satellite?

Kranky asks: "My company is looking at doing bi-directional TCP/IP over satellite, ie. data over satellite with a satellite backhaul as opposed to modem backhaul, and being the solo IT pleb here I was wondering if anyone had any recommendations for gear to use to achieve the goal or if they'd done similar and could give any pointers. Basically we're looking at 512kb/s [in both] directions and I'm wondering what sort of gear we'll need for the link, as well as any tips towards curing the inevitable latency issues. I assume there will be a cache and routers at either end (remote site will use us for internet access) but having never come across doing this whole IP over satellite thing before I have no real idea what we'll need. Any recommendations, pointers, or links would be appreciated."

Comments

Standard reply

[RabidMonkey]

I found some great resulting using google ...

http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe =UTF-8&q=bidirectional+satellite+internet&spel l=1

here's the info you need

[Anonymous Coward]

what sort of gear we'll need for the link

A satellite dish, and a satellite. Don't forget the satellite, many people forget this essential device.

any tips towards curing the inevitable latency issues

Simply change the speed of light on your immediate area, and latency issues are solved!

I think this is enough to get you started! Hope this helps!!

Re:here's the info you need

[n9hmg]

On the mod to C, he may be kidding, but he's got a point. Some latency issues can't be solved, except by reducing the latency. You call yourself an IT pleb, so I take it you're doing business work. If it's to supply email and web access to your business, the latency really won't hurt much, for most things. If you're planning to provide remote access over the link, find a lower-latency link. Interactive work with significant latency is very nearly impossible. Also, satellite latency is much more than roundtrip time. You're in a huge collision domain, covering what, 45% of the Earth's surface? I don't know how they resolve it, but I know that on my Sprint Broadband Direct (one central tower on a mountaintop, covering much of the northern Colorado Front Range), I get pingtimes as low as 40ms, and as high as 6000ms. Seems there's a lot of "waiting your turn". I can't imagine what it's like over satellite, but unless there's a seperate channel for every single user of the transponder, you face the same problem, only worse. In space service, you may have access to more frequencies than in terrestrial broadcast protocols, but you're still limited.
If you're going to be doing remote access, your users will probably be happier coming in over a 33.6Kbps modem link (if you can keep internal surfers under control).

Re:here's the info you need

[aminorex]

Now most network engineers, when asked to adjust the
speed of light, will just look at you like you are
crazy, but in fact, given that you can adjust the
electrical permittivity and magnetic permeability
of the medium (in this case, free space), it's
actually a no-brainer: Just frob the mu-zero and
epsilon-zero numbers until your ping times through
the bird are optimal.

I have permittivity and permeability modulators
ready to ship. Unfortunately they are locked
up in Nigeria in customs, but if you would care to
send me your bank routing number, I could deduct
the small customs fee, and in return cut you 10%
of the gross on sales when they get to the states!
It's a great opportunity for a smart mover!

Latency can delay link

[grantdh]

Make sure that whatever you're using lets you configure buffer sizes and such for the TCP/IP transmission. A client of mine was using a satellite to link their networks in head office and a mine in the back of nowhere. They used a large number of transponders on the satellite but weren't getting anywhere near the transfer rate they should. It was all due to the TCP/IP stack not sending on packets until it had received ACKs for those it had already sent. Given the small pending buffer size and the high latency of sending packets up & back twice (from HQ to site then the ACK coming back), it could only send a few before it had to stop & wait. Increasing the buffer solved the problem.

They were using NT and Citrix (this was back in 1997) and had to hack the registry on the gateway machines, but once it was done they got the expected bandwidth.

First thing to check, of course, is what bandwidth you'll need between the remote site and your HQ (could be high if you're going to use the link to hook them into the 'net). Next thing is figure out how many transponders you'll need on the bird to give you that bandwidth. Then figure the cost of using that many transponders. Once you recover from the sticker shock, you can determine whether they get a slow email/news only link or a full high-speed surfing link :)

Sorry I can't give you exact details - I wasn't doing the technical aspects of the project and haven't kept up with satellite pricing lately...

Latency....

[jsimon12]

It is ok if you have no other solutions, but be aware that the latency is mind numbing at times, especially for Internet access. The geosync orbit of the satellites adds almost a half a second to the round trip (and that is simply the electromagnetic signal traveling the 80,000 miles it takes to get there and come back), so on average your best ping will be at least 900-1000ms, least that is my experience with bidirectional satellite Internet access. Other then that it is good for transferring large files and stuff, just tweak your TCP/IP stack, just sucks if you have to do lots of small files or shell access, they are doable, but the latency will drive you nuts.

Why do you "have" to go satellite? Is terrestrial wireless an option?

Latency 2

[jsimon12]

...as well as any tips towards curing the inevitable latency issues...

Really not going to cure the latency issues, since the main problem involves the speed of light being limited to 186,000 miles/second and the satellite being in orbit about 40,000 miles up, meaning 80,000 miles both ways, in turn equaling about half a second of travel time. So sure you can tweak the TCP/IP stack, but the main problem is you will be lucky to ever get a ping better then 600ms, more then likely you will get something on the order or 1000ms or worse.

Re:Latency 2

[crmartin]

Mild quibble: a geosycnhronous satellite is only about 18,000 miles "up" -- geosynchronous orbit is 22,300 miles from the center of the Earth, and one Earth radius is about 4,000 miles. But I've observed the ping time to be 770 +/- 35 msec in a configuration that I was trying to work with. (There's a lot of other delay in there in things like the signal processing of the very low level signal.) Thus the basic point is correct, even if the arithmetic is wrong.

Here's research about it

[Isomer]

The WAND Research group did a lot of research about this several years ago, when NZ's bandwidth was a piece of string and people were investigating using satellite for most of NZ's traffic. Their publications are available on their website. You probably want to look at all the ones that mention a high bandwidth delay product. basically issues you have are not having a large enough tcp window size, and the latency on connection setup/tear down. The tcp window size can be easily tuned on most OS's (including windows), the latency on connection setup issue can be resolved by using proxies at both ends that forward from one to the other and keep their connections open.

Starband

[jaydho]

My family lives way out in the woods (no phone, solar for electricity.) For the past couple years we've had Starband. It is really solid and can get 300kps+ download speeds, uploads won't come close to what you're wanting, probably 20kps max. However, they offer a more expensive (monthly fee) for businesses that need more badnwidth (probably 400kps downloads 100kps uploads), I think instead of the $79 we pay it is about $149 for the higher speed and they may call this "Plus" service. You also get a dedicated IP address... Definitley worth checking out, good luck to you!

Hire an expert

[anticypher]

Basically we're looking at 512kb/s [in both] directions

For the prices you will pay for 512kb/s, you can afford to hire an engineer who has done this before for less than your first month's bill. If you have so little clue "being the solo IT pleb here" you have to ask /., then your company is going to be in for some very nasty surprises. A company with only one IT guy doesn't have the budget for what the satcomms companies will propose, 512k with both/several ground stations, maintenance contracts, SLAs, installation, training, commisioning, licensing, etc.

Others have pointed out the technical problems you will face, TCP slow start vs. transaction mode, TCP windows, TCP/UDP/ICMP timeouts. Those technical problems are small compared to the administrative, billing, negotiation and regulatory problems you must deal with. Find an expert, pay them what they are worth, and avoid being screwed by the satcomms companies. It will be worth it, even in the short term.

Packeteer was working on specialised satellite gear, but I don't see anything on their web page. Ask them, their boxes work great for tweaking long latency and high congestion links. Somehow you will have to tweak the machines on both sides of the link, either at the router level or each machine's TCP stack. Consider not allowing "interactive" traffic, especially not web browsing, or putting some severe restrictions on which web sites the lusers can view.

the AC

Re:Hire an expert

[SirLeNerd]

The most costly part of running a satellite operation is the bandwidth. I'm the operations/engineering manager for a satellite provider in Canada and I've experienced this first hand.

Depending on your choice of systems you can get anywhere from approx 590ms to over 1000ms. We operate 3 different flavors of satellite services.

A SCPC (Single channel per carrier --> think dedicated) with a frame relay core. Very reliable and average pings are 650ms. This system even supports voice over frame technology too!

The other system is a dedicated IP based TDM/TDMA system (Time Division Multiplexing/Time Division Multiple Access). The unit does IP spoofing (ie does local 3way TCP handshaking) etc... Ping times with our setup usually come in at about 900ms (based on timeplan and a few other parameters)

Since you are not driving a business with this, your needs will differ. Finding an expert to help you would be very benificial.

Personally I believe you would be best off with an SCPC solution since you have only 2 sites (HO and a remote).

Best of luck.

Simple solution.

[cybermace5]

Head down to the local hobby store and pick up a few model rocket kits. Start with one of the ready-to-go plastic ones, then gradually work up to a multi-stage D engine model. Go to college and get a complement of engineering and science majors, all doctorates. Design and build a liquid-fuel launch vehicle, and place the satellite of your own design into orbit.

You could skip a few steps, and rubberband enough Estes model rockets to an 802.11 wireless access point, trailing a really long Ethernet cable.

Hughes solution "helps" tcp streams...

[jvanick]

You still have the latency issues, but one of the Hughes DIUs actually gratiutiously(sp) acks the tcp packets on both sides... much like the old telebit PEP based modems... they also do http cacheing. Their satellites are LEO, so you've got about 750ms RTT to deal with between your location and their headend... Like other posters have said, it's good for bulk non-attendated data transfer, but to actually be sitting there using it for day to day activites, it's kinda painful. (Try to run a ssh or telnet session over a satellite link some time... you gain a whole new respect for using ed :)

MS Windows Required?

[Sloppy]

I was looking at some stuff related to this a few weeks ago, and I noticed they all seemed to have one thing in common: they don't have "normal" interfaces.

Instead of giving you an ethernet interface like you get with DSL or a cable modem, these things (at least the ones I looked at) all required you to use a weird USB box, that had to be plugged into a machine running Microsoft Windows and some proprietary drivers.