* The long and short of P2P apps
Though not all peer-to-peer applications are evil, they are frequently recreational in nature. As such, they tend to generate network traffic that businesses often like to limit, usually by means of network monitoring and traffic-shaping tools.
The primary reasons are three-fold. First, the way P2P applications work can suck up a lot of unnecessary bandwidth and degrade the performance of legitimate business applications. Second, since the Napster brouhaha, people tend to associate P2P applications – which allow desktops to share files directly – with the potential for copyright infringement and corporate liability.
Finally, P2P apps traversing the Internet can be cunning, circumventing the traditional security set up in firewalls and intrusion protection systems. This opens the enterprise net to potential risks, should viruses or other malware slip onto the network.
With a P2P application running, a PC acts both as a client and a server. It becomes a peer with other PCs – local or across the Internet – running the same app. Peers deluge other peers across the network with queries in search of files they want, often consuming huge volumes of network bandwidth.
These days, it’s not enough just to block the TCP or UDP port number associated with a known P2P application to deny access. Many P2P apps use a random or manually defined port number, or they might hop across ports during a session. In addition, some apps might sneak onto your network using a well-known port, such as HTTP port 80, which usually remains open for Web browsing.
The Layer-7 traffic management appliance from Allot Communications, Expand Networks, Packeteer and Peribit (and similar integrated traffic management capabilities in Cisco routers) identify the application’s pattern within the TCP payload to distinguish it. This allows you to set a policy for what to do with a packet flow of this application type (block it, rate-limit it or otherwise assign low priority to it, for example).
Louisiana State University told Joanie last year, for example, that it created a policy using Allot’s NetEnforcer traffic-shaper that allowed students to download music files but blocked music uploads over the Internet to guard against music-sharing litigation.
