If you are a corporation in search of disaster recovery networking solutions, a first responder who may need connectivity from anywhere at any time, or you simply need broadband internet connectivity from remote locations you have probably considered that satellite may be your only reliable option. In the midst of a disaster many businesses and first responders may find themselves without communications of any kind due to the loss of terrestrial infrastructures, or the lack of it ever existing in the first place.
The problem is that most business professionals and emergency service workers do not have a complete understanding of the satellite business and the idiosyncrasies of communications via satellite, and why should they? Satellite communications is not their profession. In the quest for a satellite internet service provider there are certain questions you should be prepared to ask before you get locked into a contract for services that won’t satisfy your needs:
1) Do you have Non pre-emptible satellite space segment?
Satellite operators such as SES Americom, Intelsat among others lease space segment to satellite service providers. There are different levels of protection available in varying price ranges. Many service providers will opt to contract for pre-emptible space segment because it’s much less expensive and they can make larger profit margins which they may or may not pass on to their end users. Pre-emptible space segment gives the satellite operator the ability to deny access to the satellite for the service provider in the event of an on board equipment failure, or to make room for a service provider who is willing to pay the Non pre-emptible premium.
During large scale disasters such as the hurricanes in the Gulf States in 2005 many pre-emptible segments of satellite space were cleared to make room for government requests for satellite service leaving other service providers with no access. If you are considering contracting for service for disaster recovery applications it is highly recommended that you find service providers that guarantee that they have contracted for Non pre-emptible space segment. The service provider should be able to provide you with evidence of their service agreement with the operators if you ask. You may pay a little more each month for your non pre-emptible service, but at least it will be available when you most need it.
2) What is your “Over Subscription” or “Contention Ratio”?
Most satellite service providers who are providing Internet services are operating systems that use TDMA (Time Division Multiple Access) based systems. A TDMA system is normally controlled by a central hub location which will command the remote units in the field to transmit their data when the hub is ready to receive it. This allows for many remote units to share the same slice of bandwidth improving the overall efficiency of the system. The transmissions from the remote units are sequenced at a very high rate, many times per second, which makes the service appear to be continuous.
However, the more units that are added to the system, the slower the service will be. A true enterprise level operator will never allow their contention ratio to exceed 20:1 or essentially 20 terminals per segment of bandwidth. Many operators that offer lower grade services will over subscribe their systems as high as 40, 80, 120:1 or more. Some operators may not be willing disclose this information to their end users. If a service provider will not tell you their contention ratio, you might consider looking elsewhere as their ratios are likely to be high. This will directly affect the quality of the service you receive. Enterprise level operators with contention ratios of 20:1 or less will charge more for their services since they have fewer users for their contracted space segment. But, you get what you pay for.
3) What is your system Latency, and does your hardware or software include TCP/IP acceleration?
Any IP transport platform will have a certain amount of latency that is inherent to the structure of the system. Latency is normally measured by how long it takes for a TCP/IP “Ping” to be sent to a server on the other side of the transport link and be returned back over the link to the point of origin. Satellite systems, due to the physics involved will have much higher latency figures than any terrestrial link. Data is transmitted to the satellite at the speed of light, or 186,000 miles per second. The satellite is located 22,223 miles above the equator.
For a ping to make its round trip it must travel up to the satellite, back to earth to the server, up to the satellite again and back to the origination point. This is a round trip is approximately 88,892 miles. When calculated with the speed of light, in a perfect world the round trip will take about 448 milliseconds. When you add in coding delays and processing delays you can increase that figure by 100 to 250 milliseconds. On an efficient system, a round trip ping should take between 550 and 700 milliseconds (225 ms one way in each direction).
Many lower grade systems on the market today will actually return ping times of 1200 milliseconds or greater which is too slow to allow for functionality of certain software applications. Some system operators have added TCP/IP acceleration products to their equipment. This can either be a hardware or software solution. Acceleration of TCP/IP does not speed up the actual transmission as it is already being transmitted at the highest speed possible, the speed of light. The acceleration is achieved by modifying the TCP protocol in ways that allow for more efficient transmission over high latency networks such as satellite. Acceleration can significantly improve the speed of loading web pages, so it is a highly desirable product to have. Most of the products are not capable of accelerating encapsulated data such as VPN’s, but the system should still pass that data, however more slowly. Be sure to ask whether or not the system has an acceleration product included.
4) Does your system support VoIP, VPN, and Streaming Video transmissions?
If you have certain applications that you intend to operate, be sure to inquire whether or not these applications are supported on the system. VoIP (Voice over IP) for telephone connectivity is becoming a very common need in satellite communications. All types of users from emergency services to business continuity are asking for telephone connectivity. The biggest concern most prospective users of VoIP over satellite have is that the latency will be too high for effective voice communications. This has largely been proven to not be true. In fact, most cellular telephone systems will experience as much or more delay in their systems than VoIP over satellite. Most satellite providers will support these systems, but if the system latency is more that about 800 milliseconds, you may experience difficulty carrying on a conversation. Some service providers will also sell VoIP equipment. If you choose to purchase from them, or on your own you will want to make sure the equipment includes good voice compression.
Most off the shelf VoIP systems that are not designed for use with satellite will occupy between 40 Kbps and 90 Kbps of bandwidth to complete each call. If you purchase 128K of satellite uplink bandwidth you may consume all of your bandwidth with one or two phone calls leaving none for internet access for your computers. There are compression VoIP systems available that have been designed for use over satellite that will use as little as 8 Kbps per phone call and the call is toll quality. There are even compression systems that will allow for a 1544 Kbps T1/PRI connection over less than 256 Kbps of satellite bandwidth. You will also want to inquire about connectivity to the PSTN (Public Switched Telephone Network). When the signal lands at the hub it will need
to connect your VoIP traffic to a telephone line. Some service providers will provide this service for a fee; some will not provide it at all, so be sure to ask.
If you need to operate a VPN over the system, keep in mind that it will likely not be accelerated over the satellite. Acceleration of VPNs can be achieved with external hardware; however it is normally up to the customer to provide that equipment. There are some systems, mostly consumer grade, that will not support VPN’s at all or there are additional charges so be sure to ask. The same goes for Video transmissions from a streaming device, or a web cam. Video streams are highly bandwidth intensive applications and most service providers will require dedicated bandwidth for these applications. The pricing for dedicated bandwidth will be substantially higher than the shared ratio pricing as it consumes 100% of the bandwidth 100% of the time. If you are planning to stream video to multiple receive sites it is recommended that you stream the video over the satellite to a server, and allow other users to get the stream from the server. This way there is only one active stream over the satellite where the bandwidth is expensive.
5) Do you offer CIR or CRA services?
CIR (Committed Information Rate) and CRA (Committed Rate Assignment) are different acronyms with the same meaning. It is dedicated satellite bandwidth that is usually required by the service provider if you intend to operate high bandwidth applications such as video streaming over the satellite. Most enterprise level service providers offer CIR/CRA packages, most consumer level operators do not. The pricing for these services will be significantly higher than shared ratio services, so be prepared. Some providers also require CIR/CRA services for VoIP. Be sure to inquire if this is something you need as some operators may not volunteer this information until it’s too late.
6) How many public IP addresses do I get?
Many consumer level services do not assign public static IP addresses for you to use. This is primarily why they don’t support services such as VoIP and VPN. Enterprise level providers usually provide at least one address, some will provide more. Most providers will give you a fixed number of addresses with your service and charge you if you want additional static IPs. The recommended way to avoid the additional charges is by using your own router on the system and natting your own addresses. Some systems will not support natting so be sure to inquire if this is what you need.
7) Do you have a FAP?
A FAP or Fair Access Policy is a set of rules that you agree to abide by when contracting for their services. They also will include certain restrictions on your service. Read this policy very carefully as the providers like to include wording that can seriously restrict your usage. Some service providers will “meter” your throughput on the system. If you reach a certain level of usage, usually recorded in Kbps, or Mbps they may restrict your bandwidth to a low level, or cut off your service entirely until the next billing cycle. It is very difficult to measure your own usage since most people have no Idea how many Kbps are sent or received when loading a web page. The FAP is also where the provider will spell out the rules of usage concerning applications such as streaming video and VoIP. Going over that document with a fine toothed comb will be in your best interest.
What will be my actual measured speeds?
The service providers will sell you a specific rate plan that will have an uplink or return data rate, and a downlink or forward data rate. This will usually be expressed in a manner such as “128 x 512” or sometimes “512 x 128”. The larger number will always be the forward channel which is your downlink as a user. Most providers will not tell you that the speeds include IP overhead. Every internet system whether its satellite or terrestrial uses IP protocols that require a certain amount of bandwidth to process the IP traffic. Because of the overhead you can expect that your actual measured payload speeds will be around 20% lower than what you are paying for. Actual speeds can be measured by running a speed test from a PC over the satellite link.
If the service provider has their own speed test server at the hub location this will give you a more accurate test of the satellite link than an Internet based speed server. The internet based servers have too many variables to obtain accurate results since the data is being transferred over connections that are not under your control, or theirs. Most systems will be similar in their IP overhead usage, but be aware of this when you purchase your service. If you don’t think the speeds will be high enough when you factor in the 20% overhead you may want to consider a higher service level plan.
9) What Pricing plans do you offer?
In your search for a service provider you will likely encounter a multitude of pricing plans. Each provider will create pricing structures that meet their business model, and that will give them an edge over their competition. Because of this you may find it difficult to compare price. All providers will offer full time 24x7x365 service plans. Some will also offer plans based on usage, and some will sell daily or hourly plans. There are even providers that will sell service for a fixed number of days each month. These plans can be attractive as you will not likely use a system designed for disaster recovery every day of the month, so why should you pay for full time service? If you are comparing price between providers it is easiest to look at their full time rates to determine the cost. However, keep in mind that operators base their pricing on their cost for the satellite space segment. If they are charging less it may be because they don’t have non pre-emptible space or because they operate with high contention ratios, or both.
10) Do you offer other services such as terrestrial connectivity and collocation?
Be sure to inquire about value added services such as collocation space and terrestrial connectivity. Unless you are only buying internet access and have no need for VoIP, streaming, or data backup, you will likely need these services. Some service providers will provide connectivity to the telephone network, and some will not. If you need dial tone you will probably want to contract for that as well. For disaster recovery solutions it is highly recommended that you originate your dial tone from a safe location that is far away from the affected area.
In many disaster scenarios the terrestrial connectivity including cellular phones will not be available. It is important that this is taken into account when designing a backup network. Some of the satellite providers will also offer services to back up corporate or government server data at the satellite hub location. This is highly beneficial to the customer as it provides both off site storage of valuable data, and easy access to that data via the satellite when it is most needed. A satellite hub with a collocation facility can be a powerful tool, and should be highly considered when contracting for satellite services.
This article was written by Bob Exum who is a 24 year veteran in the communications and satellite industries.