Why TCP optimisation has become more important than content optimisation
Since the very early days of 2G and 3G deployments, mobile operators from all around the world have been deploying and using content optimization platforms. The reasons for deploying these technologies were pretty straightforward. Bandwidth at the 2G and 3G radio layers was pretty low compared to bit rates that were available on wireline networks, so reducing the bit rates of the ever increasing amount of video streams helped save bandwidth at the radio layer and hence costs. At the same time reducing the video bit rates by using video transrating and transcoding techniques also helped improve the subscriber experience as it is better to keep a lower quality video stream steadily flowing rather than a high quality video stream stalling all the time.
A couple of recent industry evolutions are now forcing mobile operators to rethink how to optimize their subscribers’ traffic. Since the Snowden revelations the internet has seen a massive surge in encrypted traffic (https). Speaking to several mobile operators in Europe we are hearing that in many countries between 40% and 50% of all internet traffic is encrypted these days, and the trend is still going up. Also videos are delivered more and more over encrypted https instead of over unencrypted http. In addition LTE technology is capable of delivering very high bandwidths to mobile users at much lower costs (per bit transported) than 2G and 3G technologies. So the primary motivation for deploying video optimization platforms which originally was saving costs, is now shifting more and more towards either differentiating the subscriber’s quality of experience or to make use of this technology for specific traffic only instead of for all data traffic. Examples of selectively using video optimization are to optimize videos on the 3G network but not on LTE, or to only optimize subscribers that are on specific tariff plans.
Given that less and less traffic can be ‘content optimized’ due to the increasing percentage of encrypted traffic on the network, mobile operators have started to focus heavily on TCP optimization. Over 90% of all traffic on the mobile network is TCP based, and therefore a TCP optimizer can optimize almost all traffic on the network regardless of whether that traffic is encrypted or not. Indeed, TCP optimization works at the TCP layer, which in the OSI model is the layer sitting on top of IP, but below the encryption and application layers. TCP optimization is used to enhance the subscriber’s quality of experience in two ways. First, it helps to increase the peak and average bandwidth that a subscriber can enjoy over the mobile network and hence it increases the quality of experience. You could argue that because of this, it also helps to make more efficient use of the available radio spectrum and as such provides a cost benefit. Second, and this is very often overlooked, this technology also helps to reduce web page load times. One of the most frustrating experiences for mobile subscribers is that very often it takes so long to load your favorite web pages or open your facebook home page even on a high bandwidth connection. It is important to note that web page load times are not so much impacted by the available bandwidth but much more by the latency on the mobile network, and latency on mobile networks is much higher than on wireline networks. So TCP optimization not only delivers faster downloads but it also helps to keep the latency in the mobile network at much lower levels than without TCP optimization, ultimately leading to faster web browsing experiences for the mobile subscribers.
Mobile operators that have started trialing or deploying LTE Advanced have also noticed that TCP optimization will be important to achieve the maximum possible throughput rates that these new technologies promise. So TCP optimization should not be looked at solely to improve the performance in some 3G areas with poor coverage, but as a key building block on the Gi LAN that will help mobile operators achieve the maximum possible throughput and hence maximized subscriber satisfaction on any radio technologies that get deployed today and in the future.
Technically speaking, what a TCP optimization platform actually does is decoupling any TCP connection between a mobile client and a content server in two separate TCP connections by acting as a full TCP proxy in between as shown in the picture below. The TCP proxy ensures that the TCP flow and congestion management techniques are fully adapted and tuned to the specific characteristics of the networks the proxy is connected to. The bandwidth, delay and packet loss characteristics from the cellular network are very different from the IP backbone network and the internet and therefore the TCP optimization proxy is capable of getting the maximum efficiency out of the networks it is connected to. Satellite networks also exhibit much higher latencies then wireline networks so also in that market sector you will find TCP technology being heavily used to optimize overall performance over satellite links.
Even though TCP optimization as a technology is not new (it has been deployed for many years), the heavily increased focus of mobile operators towards this technology in the last 9 to 12 months is. And given that TCP optimisation is agnostic for the encryption and application layers, plus the fact that we see great benefits not only for 3G and LTE, but also for LTE advanced, it is a technology worth exploring for any mobile operator.
Interested in hearing more? Stop by our booth at MWC Hall 5, G11