Pay Attention To QOS While Doing CCIE VOICE,In Case You Have To Find P2P Traffic In Your Enterprise Network, Read The Catching The Torrent Guy Post].

I am positive you all know that. I also hope that you're ensuring it is not hogging your enterprise network; in case you have to detect P2P traffic in your enterprise network, go through the Catching the torrent guy post.

Service Providers are not so fortunate - a few Internet surfers claim using infinite amounts of P2P traffic is their birth right. I don't really care what kind of content these users transfer, they are consuming massive amounts of network resources because of a combination of P2P client behavior (which is clearly "optimized" to grab whenever possible) and the default TCP/QoS interaction.

Let's begin with the ccie voice lab:

P2P implementations (for instance, BitTorrent clients) open a huge amount of simultaneous TCP sessions. 200 concurrent sessions is a very "reasonable" number and a few people claim that the 10 new sessions per second limit included by Windows XP SP2 is lowering their speed. Now you know how many sessions they tend to open.

P2P client could saturate any link for quite a long time. I am a heavy Internet user, but I still use around 1% of my access speed (long-term average). A P2P client can bring the long term average about 100%.

I would not mind the reckless implementations of P2P clients if the Internet will be an infrastructure where every user gets its fair share of bandwidth. Sadly, the idealistic design of the early Internet makes sure that (using default router settings) each TCP session gets the similar amount of bandwidth. A P2P user with 200 concurrent sessions thus gets 200 times the bandwidth of another user downloading her e mail with a POP3 session. Clearly not a mutually beneficial situation (for anyone however the P2P guy) that could very easily lead to "a few" irritated calls to the SP helpdesk.

What we would need to deal with the P2P users is per user (per IP address) queuing, which is not available on any router that I'm acquainted with (let alone on any high-speed platform). In case you have more information, make sure you share it in the comments.

The most effective alternative I am aware of is a dedicated box like Cisco's SCE that can perform per user measuring with real-time actions. Sadly, we cannot deploy SCE at each bottleneck in the network; it is often deployed anywhere between the access and core network with plenty of bandwidth surrounding it.

To address the P2P challenge with SCE, you can define extremely smart bandwidth groups or you might use SCE to monitor per user quotas (in fact per IP address quotas) and to act once an user surpasses her quota - for instance, by hard limiting the user's bandwidth or remarking her packets having a low priority DSCP value which can then be used to select a different (low priority) queue on congested links.

Are you wondering if SCE will help you fix your difficulties? Why don't you check our ccie voice workbook ; these workbook has implemented SCE based solutions in more than 20 large SP networks world-wide. Alternatively, you might want to join our ccie voice training.