Bi-Directional IP Over Satellite? 51
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."
Standard reply (Score:2, Interesting)
http://www.google.com/search?hl=en&lr=&ie=UTF-8&o
here's the info you need (Score:3, Funny)
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 (Score:2, Informative)
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 (Score:4, Funny)
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 (Score:5, Insightful)
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...
Re:Latency can delay link (Score:2)
Another common method for reducing the effect of a large latency on TCP is to place special proxies at either end of the satelitte link. These proxies will fake TCP ACKs in order to stop latency problems. The also handle any error recovery by buffering the packets they have received, until they receive the real ACK from the other side of the satelitte link. As far as I remember, there was some jiggery-pokery involved in dealing with all possible combinations of SYN and FIN flags but I cannot remember the details.
Steve.
not worth it... (Score:1, Informative)
Latency.... (Score:4, Informative)
Why do you "have" to go satellite? Is terrestrial wireless an option?
Latency 2 (Score:3, Informative)
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 (Score:2, Informative)
Duh.... (Score:1)
Re:Duh.... (Score:1)
Actually (Score:1)
Huh? (Score:1)
Re:Huh? (Score:2)
I'm guessing they are using IP over avian carriers [faqs.org] to get around the altitude issue.
Here's research about it (Score:5, Informative)
Why satellite? (Score:2)
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.
Zmodem (Score:2)
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?
Re:Zmodem (Score:1)
Re:Zmodem (Score:2)
Steve.
BER (Score:1)
Re:BER (Score:2)
Re:Zmodem (Score:2)
Why Satellite? (Score:2)
Re:Why Satellite? (Score:1)
Remote locations... (Score:2)
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.
Re:Remote locations... (Score:1)
Telstra has such a service (Score:2)
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 [bigpond.com]
Starband (Score:3, Informative)
A (hopefully) helpful reply (Score:1)
Hire an expert (Score:3, Insightful)
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 [packeteer.com] 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 (Score:1)
Re:Hire an expert (Score:2, Informative)
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.
If latency could be a problem... (Score:1)
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)
Re:If latency could be a problem... (Score:2)
Well if on that day the sun appears to be right behind your satellite to your dish, it could make things harder for your receiver.
And if you use microwave bands - there's always rain.
Satellite is good for remote locations - no cables, no towers nearby with access to cables, no nothing.
But use the cables when you can.
Satellite bandwidth is fine for broadcasting because everyone gets the same info and latency usually doesn't matter. Not good for situations when each user wants different info.
I don't see it changing unless you can increase bandwidth using spatial means (e.g. multiple satellites working together to send "holographic" signals which are resolved by each receivers differently - they each see a different "picture"). Someone is probably working on that somewhere.
There will always be latency until someone finds a way of sending info faster than light, or manages to launch and run lots of low orbit satellites cheaply.
Simple solution. (Score:3, Funny)
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... (Score:2, Informative)
MS Windows Required? (Score:2, Insightful)
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.
Recommendation (Score:2)
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.