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Cogent Depeers China Telecom


On March 5th, 2012 at 14:00 UTC (10:00 PM China Standard Time), Renesys observed that Cogent (AS174) and China Telecom (AS4134) appear to have dropped their mutual connectivity. Prior to this time, China Telecom regularly announced about 3000 prefixes to Cogent. After depeering, this ASN adjacency no longer exists in the global routing table.


In addition, the depeering appears to have resulted in an increase in transit from China Telecom to Sprint (in grey below), as expected, since Sprint is China Telecom’s paid transit provider of last resort:


Finally, we can see the impact of the Cogent-China Telecom depeering in our traceroutes. To pick just one example, we see that, prior to the depeering, our traceroute collector in Barcelona was almost exclusively using Cogent to reach China Telecom networks. After the depeering, traceroutes must take paths through one of China Telecom’s transit providers, either Sprint (AS1239) or Level3 (AS3356):


So, what happened? This disconnection will increase China Telecom’s transit costs (mostly to Sprint) and will decrease Cogent’s revenue by losing multi-homed customer traffic destined for China that will now take shorter alternative paths through Level3 or Sprint.
So, is this evidence of another Cogent peering dispute or was there an equipment failure in San Jose, California where the two providers used to connect?

It is important to note that, unlike prior depeerings, there is no complete loss of transit between anyone on earth as a result of this event. Even those brave souls who are single-homed to Cogent will still have paths, because Cogent will peer away their traffic toward Level3 or Sprint, both of whom count China Telecom among their customers.

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  • This comes at a very inconvenient time for Cogent, who are still recovering from the massive loss incurred by the MegaConspiracy bust. I’d like to think that there’s a noble reason (like, Cogent was fed up with abusive traffic or wanted to stress net neutrality), but it’s more likely a business issue.
    We are seeing an increase in sales activity by the Cogent drones as a result of their latest customer losses, frantically pumping special offers out of the door. Personally, I’m going to wait for the point in time when a cogent drone offers to actually pay ME for taking up their routes. 😉

  • Dave

    There are circumstances where de-peering someone may actually improve Cogent’s revenue. If, for example, total available capacity increases as a result of the route through the peer.

  • Joe Ferretty

    First in most, I can’t see Cogent benefiting from the increase of China’s traffic, other than the ISP’s having direct contractual peering agreement with China Telecom. Peering cost are enforced by the amount of upload traffic being surpassed set by peering agreement. This is just another move by Cogent to avoid piracy traffic on their network, as Internet pirates are now moving away from safe havens such as Sweden to new territories that include China and Ukraine, as they try to avoid prosecution for illegal file sharing, according to experts. This is just my two cents.

  • Joe

    I would guest cogent don’t have much of enterprise customers, that’s why they don’t care about peering with China telecom.

  • vpn

    I am very happy to see this. I am working in China and everything is blocked here. They do not respect anything then their silly Internet rules. I must pay every month VPN services to pass their stupid restrictions and great firewall.

Whois: Doug Madory

Doug Madory is a Director of Internet Analysis at Dyn where he works on Internet infrastructure analysis projects. Doug has a special interest in mapping the logical Internet to the physical lines that connect it together, with a focus on submarine cables.