Tunnel vision is a rather serious medical condition and the Internet or at least a number of service providers could be at risk if not treated soon enough.

Symptoms of inter AS (Autonomous System) tunnel vision are many slower connections with IPv6 compared to IPv4 with some failing all together. Reason is that tunnels, especially inter-AS tunnels, can lead to long paths and non-optimal routing. Indeed a tunnel will hide routers and networks traversed and packets could emerge at a tunnel end-point at the other side of the world an untold number of routers and Autonomous Networks away. Tunnels for local access or to traverse one or two nodes that have not yet been upgraded are perfectly acceptable and often indispensable but to use them to traverse two or multiple Autonomous Networks is just plain bad business. Long AS paths lead to slow convergence, long RTT’s (Round Trip delay Time), questionable quality of service and ultimately poor experience and loss of revenue

Bernhard Schmidt illustrates this perfectly in his May presentation on IPv6 routing issues at RIPE 56 . In October at RIPE 57 Google’s Lorenzo Colitti puts the question: ‘how do we offer IPv6 content without harming user experience?’, and is rather critical of ISP’s and the high latency currently observed on many inter AS IPv6 routes.

While most major tier 1 Internet Service Providers have IPv6 connectivity on par with IPv4 between themselves, a New Year resolution, as we start 2009, should be to improve inter-AS IPv6 routing throughout the internet. One relatively easy contribution would be to activate dual stack connectivity, at no charge, to as many of their adjacent AS peers and customers on the existing interconnections between border gateways and make IPv6 routing more congruent with IPv4. This rather straightforward initiative would go a long way to help decent IPv6 routing percolate down the internet fabric and secure continuing customer satisfaction and associated revenues throughout the ecosystem.

Tunnel vision can be detrimental. Nobody wants to wake up bypassed by too many major content providers.

Any opinions, findings, conclusions or recommendations expressed in these articles are solely those of the author and are not in any way attributable to nor reflect any existing or planned official policy or position of his employer in respect thereto.