[ Contents | Post | Reply | Next | Previous | Up ]
From: Lyle Sharp
Category: Internet
Date: 03 May 2006
Time: 23:41:00 -0400
Remote Name: 24.182.111.42
A recent service call introduced us to one of many network applications that fail under high latency network conditions. Latency is essentially the trip time for a single packet in either direction. This condition is easy to test for and isolate to troublesome routers or segments by using ping and tracert commands in Windows XP. The types of applications that fail or respond so slowly as to be unuseable in high latency environments are streaming 2 way video, VOIP, VPNs, and any other application where network communication timing is critical. Most applications developed for Internet use have a pretty high tolerance for latency below 100ms for a packet to travel round trip. Some, like VOIP do not. VOIP works best in conditions where latency doesn't exceed 30ms. Anything higher and the human hear can discern the lag. This is important to many of our clients because VOIP and streaming media applications are becoming more popular as broadband Internet connections become more common. However, not all broadband Internet connections are created equally. Satellite based Internet connections like Direcway have huge latency problems due to the distances each packet must travel. Each packet must travel more than 44,000 miles rountrip to reach a satellite and return to earth. By contrast, the Earth at the equator has less than a 4,000 mile circumference. Even at very near the speed of light, this trip to space and back creates a built in latency issue of greater than 280ms. A comparable trip around the surface of the Earth at the equator would take less than 35ms. This effectively kills the potential for VOIP or any other two way communication protocol that needs lower latencies to work for a satellite based Internet connection. Residential cable modem networks typically have higher latency as the customer base increases on the local segment in your area. This means packets are waiting for the local line to be available before taking their turn using a crowded pipe. In our call today, an overcrowded cable network was at the root of our client's inability to host a web conference. In the cable company's defence, they do have more uncrowded pipe available, but usually not for residential services nor at residential service prices. DSL services can also fall victim to high latency conditions as switches begin to carry more traffic than they were designed for. These conditions occur more frequently in recent years with the large expansion of the broadband cable and DSL markets. ISDN/T-1/OC-??? and other high speed telcom offerings are premium business connectivity solutions designed to provide gauranteeed bandwidth rates and low latency conditions regardless of the other clients provided for by that communication company. The pricing, of course matches the premium connectivity service tag and hardly competes with residential connectivity markets. What does this all mean? It means there is a good reason why businesses pay for the premium connection services. Whether your business can get away with using lower cost residential connectivity solutions depends on what you need to do with your Internet connection. Consider your proposed use before you sign that two year service contract with the low rate. If you still have any questions, call us. We'll be glad to help. For our own client, the web conference was a solid short term requirement and Advotech pitched in by lending an office space and our network connection to the client after determining the cause and with no other resolution possible before the scheduled conference. They seemed to enjoy the unintended visit and the conference went off without a hitch. We love to see our clients get the results they want, but have recommended that this client either book a virtual office for such future events, or invest in a better Internet connection. Unfortunately, our offices are not always available for such things and leasing them out isn't part of our business model. ;-)