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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."
I found some great resulting using google ...
e =UTF-8&q=bidirectional+satellite+internet&spel l=1
http://www.google.com/search?hl=en&lr=&ie=UTF-8&o
We emerge from our mother's womb an unformatted diskette; our culture formats us. - Douglas Coupland
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!!
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...
I left my body to science, but I'm afraid they've turned it down...
you'd be better off in the long haul having a T1 trunk line pulled to your building. cheaper, not necessarily faster, but better response times (dont have to worry about the 200ms delay in getting a transmission between the ground and the satellite)
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?
...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.
money lots of money.
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.
If you are looking to connect sites in remote areas, satelliete untethers you from the phones.
If you are looking at satellite for any other reason, forget about it. Especially if you are looking to use Direcway as your solution.
Satellite give you fast transfer rates, but managing a network on the other side will be very difficult.
Conformity is the jailer of freedom and enemy of growth. -JFK
Sorry, I must have been hopped up on goofballs or something.
I changed the gravitational constant of the universe, but after your help I have been latency free!
Whatever happened to the ZModem file transfer protocol? It was optimized to work over high latency satellite connections, and did so very robustly.
I wounder if it would be possible to use it's capabilities to solve the TCP/IP latency problems. Is Chuck Forsberg still living on his houseboat in Seatlle?
An older and more expensive option may be "Satellite Frame Relay".
If you have $20K to spend on a larger dish and related hardware, you can have T1 bandwidth from anywhere. High latency of course!
Remember that with any satellite link you will experience eclipse outages at certain times of the year when the satellite is directly between you and the sun. (Your dish is then focused on a very big microwave emitter 93 million miles away!)
You will need to be able to cope with these outages somehow.
It all depends on what you want to spend, what you're going to use it for. If it's just for casual Web access, go get a DirecPC type of unit from Best Buy or a Starband unit from Radio Shack and save some $$. Those are low-end, small, cheap and they do work.
It would help if you can give us more details on how you intend to use the Internet connection. If it's mostly for hauling "bulk" data, Satellite is okay. But it's danged slow for interactive use.
One alternative to satellite that I have considered,
in order to get Internet into a remote location
(Faya-Largeau, in northern Chad, a Saharan oasis
town about 300 miles from land lines) is a tethered
balloon with a repeater. The power for the repeater
would be solar, and run up the tether. Does anybody
know of someone who has done anything like this?
UAVs are pricey, but I have no clue whether the
operating time of a helium weather balloon, or the
tether-weight vs. balloon-size tradeoffs would
make such an approach prohibitively expensive.
-I like my women like I like my tea: green-
The main telecom in Australia has a two-way satellite service available Australia wide (mostly for rural areas). They also have a 1-way satellite with modem back channel.
Perhaps you can check their web-site and e-mail their tech's - perhaps they'll be willing tell you the setup they use.
Failing that - are there any slashdot readers that have this service? - if so, what is your setup?
Their two-way satellite web-site is here
/..sig file not found - permission denied.
you're right, actually..except that satellite communications don't use light.
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!
My employer is currently looking at the IP3 (they say cubed) product fom Kromos.com We are pleased at what we have seen so far of the product and the engineers' willingness to address concerns we have so far expressed.
You lost me here, if satellites don't use light "ie electromagentic radiation", then what do they use? Hamsters?
Basically we're looking at 512kb/s [in both] directions
/., 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.
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
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
Hemos is like...sci-fi fans;he thinks technology is cool, but he hasn't bothered to understand the science it's based on
then don't do that then !
Seriously, first ensure through the use of traffic shapers if the bad satellite network latencies are no problem for you before you go on thinking more deeply about the real implementation.
I know of an organisation where someone from management decided that for the new infrastructure they'll go for satellite instead of DSL... 'for reliability reasons'.
Well it turns out that an (extremely crappy) application they depend on is not able to accept latencies above 1sec, which the satellite turns out to have. And then one day the satellite link failed for some hours (I don't know why).
Now they still pay for the satellite they don't use plus the DSL lines they wanted to avoid... because DSL turns out to be more reliable and has far lower latencies... D'oh !
But try convincing such a suit that a satellite would be a bad idea in the first place :-) He didn't believe us and now he has to justify the consequences (= more money spent than necessary)
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.
...
The raw link BER my be poor, but that may not be what the user sees. I've worked at places that had 56K international data circuits through Intelsat and DOMSAT earth stations and satellites. From what I remember, the earth stations used special satellite modems to provide the digital data link through the analog spacecraft transponder. The only problems we had with the BER on the circuits was when the Sun was in alignment with the satellite, which increased the noise floor and temporarily interrupted the circuit.
Mea navis aericumbens anguillis abundat
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 :)
Moron moderator. A FIRST POST cannot, by definition, be redundant.
I think it really was raditaion from orbiting solar debris, I had forgetten my foil hat, or was it statis electrcity from slide rules?
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.
As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
Don't forget, these guys BUILD the birds before NASA or ESA put them into orbit so they know what they are talking about.
Disclaimer - I don't work for Hughes but I think that their service is way cool and if I needed something like this again I would contact them in a heartbeat.
Steve Gunn
You didn't even say WHY your company needs it.
If you don't know why you need it, you probably don't. If you don't say why you need it and ask such a question...
The fact that modem backhaul was an option is also another indicator.
Advantages:
1) Good for remote areas - middle of ocean, middle of desert, on some mountains (some have WiFi tho).
2) Good for broadcast.
3) Good for mobile stuff (but wireless/cellular networks are good in some areas).
Disadvantages:
1) Latency (if geosync).
2) Expensive (you said bi-directional).
3) Not that reliable (lightning, bad weather, or sun got up on wrong side of satellite, feeling grumpy etc).
Why expensive? Most geosync satellite stuff is shared bandwidth over big footprint - unless they figured out how to send and receive holographic sat signals. Good for broadcasting the same 1.5Mbps stream to 200 million people, but bad for different streams per person. Which is why many satellite ISPs died. Copper pair, coax, fibre cheaper for most populated locations - one fibre could carry as much bandwidth as a whole satellite, and doesn't have to be shared by all subscribers.