[Nanog] Cogent Router dropping packets

Joe Greco jgreco at ns.sol.net
Sat Apr 19 13:01:54 UTC 2008

> Same here... frequent packet loss.  We had Cogent GigE service for about
> 9 months if I recall - more than one major outage per month and packet
> loss issues at least once a week.
> You get what you pay for (within reason)....

Cogent tends towards being a content network, and has occasional peering
issues with other networks who wind up bearing some of the related costs.
Internally, their network earns better than average marks, but sometimes
there will be strange things that don't seem to make sense, and these may
or may not be explained or fixed if you contact Cogent.  Externally, we've
seen their history of peering problems.

We've noticed that there tend to be specific routes where Cogent
experiences problems for long periods of time.  In the last few years,
for example, if packets went through Paris or London to destination ISP's
in the associated countries, there tended to be some performance problems.
Some of these have cleared up.  It would appear to be peering and/or
congestion issues.  These would typically only affect specific
destinations, but often required analysis and workarounds to be

We've not noticed problems with major outages, but that may be because of
our location (Ashburn).  There seem to be some people who do not experience
outages, and others who experience frequent outages.  This may be dependent
on where in the Cogent network you are.

In their original business model, providing business ethernet connections
in a metro area, they're a very attractive provider, but I'd guess their
overall reliability would feel to be on par with some commercial ISP's, due
to occasional peering problems, packet loss, etc.

>From a service provider's point of view, in many places in the country,
their service is still sufficiently cheap that it could be worth
considering as part of a bandwidth mix.  Given the availability of
automated tools to manage connections susceptible to brownouts (Cisco 
OER, Avaya/RouteScience, etc), it may be quite attractive and viable to 
use Cogent in certain environments, but you have to give it some thought.

To the original poster, Cogent to AT&T (DSL, etc) has historically been 
what I'd consider to be "problematic."  For years.  Filtering out routes
that involve both AT&T and Cogent seems to work, though it may be
unnecessarily aggressive (and obviously you'd need an alternate carrier
with good connectivity to AT&T).

... JG
Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net
"We call it the 'one bite at the apple' rule. Give me one chance [and] then I
won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN)
With 24 million small businesses in the US alone, that's way too many apples.

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