Original article: Pinning down latency
Getting to grips with latency
Packet latency is a big issue in Internet-based applications (i.e. the stuff in the cloud). In conducting analysis on Internet infrastructure over the years, we have seen many patterns of connectivity. One such pattern that can wreak havoc on latency is "hair-pinning", a phenomenon where traffic takes an unnecessarily long physical path between two points on the Internet due to suboptimal routing.
The increased distance results in increased latency, and the "lag" or "sluggishness" that users experience as a result can hinder latency-sensitive online applications whether they are financial trading applications or MS SharePoint.
A couple of weeks ago (September 23rd to be exact), I noticed a small routing outage (150 globally routed prefixes) in Sakhalinskaya Oblast, the most Eastern part of Russia. We observe these types of outages every day — the Internet is a big messy place behind the scenes. The obscurity of this location piqued my curiosity and I looked into how this area gets Internet connectivity — almost exclusively through Russian provider, TransTelecom.
[T]his province connects to Japan via Hokkaido-Sakhalin Cable System (HSCS), built by NTT in 2008 to provide a shorter path from Japan to Europe over Russian soil.
However, despite the proximity to Japan, a traceroute from NTT's Tokyo Looking Glass to an IP address in Sakhalinskaya [typically follows a path from Japan to the UK and back again].
Circuitous routes like this are called "hair-pinning" in the business - this traceroute travels from Japan to London just so it can make its way back to a location just off the coast of Japan. On the Internet, geographic locality does not translate into Internet locality, and the distinction can result in unexpected latency, frustrating users of real-time applications.
Latency in the Middle East
Last week I was in the fascinating city of Muscat, Oman for MENOG 9 giving a talk about latencies we have measured into each Middle Eastern country.
While regional traffic in the Middle East often suffers from hair-pinning via European Internet exchanges, latencies to and from Europe appear to be steadily improving.
In the past, when Renesys has analyzed Middle East connectivity it was with regard to complete outages such as the cable cuts in 2008. This year, connectivity into the Middle East has been much more stable (obvious exceptions notwithstanding) and the fact that regional providers can focus energy on reducing latency is a good sign for the region. For example, OmanTel's strategy (AS8529) to reduce latency to Europe by gaining presence at AMSIX (AS1200) is paying dividends in 2011 by reducing median latency by 41ms or 20%.
Until a regional Internet Exchange emerges for the Middle East, the best regional providers can hope for is to reduce latency on the path of the hair-pinning through Europe for regional traffic!
Impact of IMEWE Activation in Lebanon
The most recent (and intriguing) development in the area of latencies to the Middle East is the reported activation of the India-Middle East-Western Europe (IMEWE) cable system at Tripoli, Lebanon. Despite speculation the activation would be delayed, there is evidence that the cable is now being actively used. Certainly something has happened in Lebanon to reduce latencies in recent days.
Thus far, development of the Internet market in Lebanon has been stifled by the country's extensive dependence on satellite Internet service — the ultimate form of hair-pinning.
[L]atencies into Lebanon separate into two modes based on delivery medium: satellite (primarily via SatGate, AS30710) and submarine (primarily via Level3, AS3356).
In the coming weeks we expect to see a dramatic shift in transit as Lebanese providers move away from expensive and high-latency satellite service to IMEWE-based service. This is likely to resemble the collapsing of satellite Internet markets which we have observed occurring in African countries almost immediately after new cable landings are established nearby.
There are many causes of latency in network performance, such as congestion and router overutilization, but hair-pinning is often avoidable. Businesses need Internet intelligence to know their high latency is a result of hair-pinning and then press their providers to do something about it! This is particularly important for mobile providers because it adds another potentially severe performance penalty to the Internet service they provide.