[routing-wg]Routing Aggregation Policy
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Barry Greene (bgreene)
bgreene at cisco.com
Wed Oct 12 15:41:10 CEST 2005
How would you enforce a policy like this (Other than peer pressure)? > -----Original Message----- > From: routing-wg-admin at ripe.net > [mailto:routing-wg-admin at ripe.net] On Behalf Of Mike Hughes > Sent: Wednesday, October 12, 2005 12:29 AM > To: routing-wg at ripe.net > Subject: [routing-wg]Routing Aggregation Policy > > Hi folks, > > Joao asked me to forward some background to an item that I > will do on Thursday. > > This is the last draft of the defunct Route Aggregation > Policy that was formulated by the LINX Council/Members, > before it was rejected as a "policy" by the LINX General > Meeting in August. > > I took an action from the LINX Membership at that meeting to > donate what we had to the RIPE community for re-formulation > into a best practice document. > > I'll give you some more background during Thursday's WG > meeting, but for now, here's the draft itself, as it stood at > the point of the rejection as an enforced policy by the Membership: > > -------------------------------------------------------------- > ------------- > Revised Route Aggregation Policy > -------------------------------- > A LINX member shall announce no more than (N * 2) + 3 > prefixes, where N is the number of maximally aggregatable > prefixes that could originate from the AS under ideal conditions. > > Prefixes are aggregatable if: > > 1. They have the same AS path > 2. They are adjacent > 3. They are of equal size and are 2**N in size where N is > an integer > 4. They start on "power of two" boundaries > 5. After aggregation, the result starts on a "power of > two" boundary > > In order to determine maximal aggregation such prefixes shall > be aggregated, and the criteria above applied again. > > This process shall be repeated until no further prefixes can > be aggregated. > This final number of prefixes is the maximally aggregatable > prefixes announced from that AS. > > In order to ensure neutrality and to guard against bias in > the measurement, announcements shall be observed at several > locations, decided from time to time by the LINX Council. > > For those members with large amounts of address space, for > prefixes smaller than /16, deaggregates up to /16 will be > permitted without penalty and all such announcements will be > considered as one, for the purposes of calculating the > metric. For example, a member with a /14 will be able to > announce this as 4 /16s and this will be counted as 1 announcement. > > Examples of aggregation calculations > ------------------------------------ > Example #1 > > If you currently advertise the following prefixes from your ASN: > > 10.123.4.0/24 > 10.123.5.0/24 > 10.123.6.0/23 > > On the first aggregation pass, you could aggregate the first > two prefixes into a single /23, leaving you with: > > 10.123.4.0/23 > 10.123.6.0/23 > > If you then aggregate again, you'll be able to further > aggregate these together into a single /22, leaving you with: > > 10.123.4.0/22 > > However, if you were advertising the following prefixes: > > 10.201.5.0/24 > 10.201.6.0/24 > > then these are already aggregated as far as possible, as > although they are consecutive, and it appears that they > could be replaced with a single /23, the first prefix, > 10.201.5.0/24 is not on a /23 boundary. > > -------------------------------------------------------------- > -------------- > > Obviously, it will need re-drafting to be more BCP-like, > rather than a policy, and don't ask me what happened to > Examples 2 and 3 ;). > > Thanks, > Mike > -- > Mike Hughes Chief Technical Officer London Internet Exchange > mike at linx.net http://www.linx.net/ > "Only one thing in life is certain: init is Process #1" >
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