[arin-ppml] ARIN 2-Byte ASN inventory and issuance

Michel Py michel at arneill-py.sacramento.ca.us
Mon Apr 11 18:59:47 EDT 2016

> Owen DeLong wrote :
> However, if you have a configuration using extended communities and full support of modern ASNs enabled on
> your router, then all ASNs are treated as 32-bit ASNs and there is no fundamental difference remaining.

Big if, and in reality this is simply untrue. For large and /or heterogeneous networks, there will be a need to deal with both for quite a number of years. Event with compliant gear, there is always some legacy stuff somewhere else that has not been upgraded yet. Using extended communities is just the same as operating dual-stack : twice the number of things to manage, and a bridge to build between the old ones and the new ones.
Two different configuration lines. Two sets of regexp to match. Limitations in extended communities that did not exist with the old ones.

I gave examples recently. Show me in the real-world where old-style BGP communities have been completely deprecated.

Moving to extended communities is time consuming, prone to mistakes, and not simple. Trying to argue that you can treat all AS numbers the same way is the same as trying to pretend that operating an IPv6-only network is simple. Let's not make with extended communities and 4-byte ASNs the same mistake we made with IPv6 : for the foreseeable future, we will have to deal with 2-byte ASNs, non-extended communities, and IPv4.

Here is the real question : do we want a grey market for 2-byte ASNs ? because as long as they are easier to use than 4-byte ones, there will be a value attached to them.

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