An Acid-Test for Service Provider Routers

by Jeff Loughridge

Business school majors learn that an acid-test ratio measures a company’s ability to pay off immediate  liabilities without selling inventory. I’m using this post to suggest an acid-test for edge and core routers in service provider (SP) networks. The analogy isn’t perfect, but let’s follow the lead of  the Acid-3 HTML compatibility test and go with it.

If I’m involved in an SP (or SP-like networks such as the mobile packet core) router RFP, I can usually gauge the vendor’s ability to play in the SP space based on a small subset of necessary features. The following list is intentionally inexhaustive.

  • ISIS – The implementation of ISIS historically has been a barrier to entry into SP networks. While OSPF deployments vastly outnumber ISIS deployments overall, ISIS has its proponents in many engineers who have maintained large-scale SP networks. The movement to IPv6 will likely increase ISIS’s popularly since its use eliminates the need for two IGPs to carry IPv4 and IPv6 prefixes.
  • IPv4-IPv6 feature parity – In a previous post, I mentioned the cavalcade of “buts” in IPv6 feature support. Being very explicit in RFPs about IPv6 is vital. You don’t want to find out after purchase that control plane protection of the route processor does not support IPv6 or something similarly frustrating.
  • Two-stage commit – A vendor in 2011 that pitches a product without the ability to change configuration and then apply the new configuration is not serious about courting SP business.
  • Solid In-Service Software Upgrade (ISSU) and High Availability (HA) Story – When I joined a Tier 1 ISP in 1998, I heard the stories from the veterans about reloading routers during and day and upgrading code at night without supervision by using the “reload at” IOS command. Times have changed. Businesses’ reliance on IP and the Internet demands five nines reliability and fast convergence after a failure. Ten minutes of downtime for a software upgrade or software defect blows your five nines budget for the year on an edge device in the SP network. (Yes, I know how SPs play with definitions and averages, but we need to be serious with the vendors in laying out requirements for uptime in today’s IP networks).
  • /31s – Many provisioning systems for ISPs are set up to select and configure /31s for internal point-to-point interfaces to avoid the waste of two addresses when using /30s for point-to-point. Let’s hope for the day when we can implement IPv6-only and spend our time debating the best practice for numbering point-to-point links in IPv6.
Keep these items in mind the next time you are involved in selecting a new router. Even if you don’t maintain a Tier 1 ISP network now, you’ll likely find yourself dealing with scaling challenges as bandwidth utilization continues to rapidly increase.
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