The recent dispute between Level 3 Communications and
Cogent Communications demonstrates why firms should use more than
one ISP, says analyst Gartner.
At the beginning of the month, Level 3 ceased its peering
relationship with Cogent, claiming the connectivity arrangement was
financially unfair – an allegation Cogent rejected.
The dispute initially led to thousands of internet users being
cut off from other users. Faced with pressure from its customers,
Level 3 relented and restored connectivity to Cogent.
Gartner said the dispute underscored the vulnerability of the
internet’s connections. The internet is a network of networks, so
for one ISP to reach the network of another ISP, it must either
peer with that ISP or buy transit through another service provider
that peers with that ISP.
When Level 3 ceased its peering relationship with Cogent,
"single-homed" customers – those who buy internet connectivity from
just one of these providers – could not reach customers on the
other network.
Level 3 not only disrupted connectivity to Cogent’s customers,
but for its own too. Multi-homed customers could still reach the
other provider, via their other ISP connections, although this may
have resulted in greater network latency (delays), said
Gartner.
Gartner said this wasn’t the first time peering relationships
had ceased, either deliberately or accidentally, and nor would it
be the last.
It said no matter how many circuits firms purchase from a single
ISP, or how reliable that ISP’s operations are, firms are
vulnerable unless they are multi-homed.
Gartner said every location that requires mission-critical
internet connectivity, including externally hosted websites, should
be multi-homed.
It said firms must buy connectivity through at least two ISPs,
and ensure that the second ISP is not simply a customer of the
first.