[routing-wg] Need for "import-via:" and "export-via:" attributes in AUT-NUM object

On Thu, 24 Oct 2013 15:05:21 +0200
Denis Walker <denis at ripe.net> wrote:

> Although the proposal had received some support when discussed recently 
> on the Database Working Group mailing list, there was some discussion 
> during the RIPE 67 Routing Working Group session that the community 
> field can be used to achieve the same result as these proposed "via" 
> attributes. However, some people have commented that the community field 
> cannot be used for this purpose with 32-bit AS Numbers. As a result, the 
> RIPE NCC was asked to bring the issue back to this mailing list for 
> further discussion.

Overloading of the community field is something that is done by current
route server operators. This is because of the lack of a proper alternative.
While it is something that works for most cases, it does not accurately
describe the actual policy.

An example:

  export:       to AS6777 action community .= { 6777:6777, 6777:64514,
  6777:64515 }; announce AS1200

This specifies that routes are being sent to AS6777 tagged with a set of
communities. Without the additional knowledge of how AS6777 treats these
communities it is not at all clear that this policy in fact describes a peering
relationship between AS1200 and AS64514/AS64515 via the Multi-Lateral Peering
service operated by AS6777.

The "import-via/export-via" attributes would allow operators to accurately
describe these indirect adjacencies, because it actually defines 64514 and 64515
as Autonomous System numbers.


Furthermore, the community-approach is problematic due to the lack of room
for specifying policies for 32-bit ASNs, which has already been mentioned in
this thread.


For the above two reasons I would like to see these attributes implemented.

Kind regards,
Martin