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Last update: 2004-03-31

End: 2003-01

Atom-Based Routing; Related Ideas

Improving global internet routing by implementing atom-based routers.

7. Related Ideas

For completeness we point to related ideas that we are aware of.

7.1. Geoff Huston's Atoms

Geoff Huston mentions `atoms' as well in HustonAtom. Huston's atoms are somewhat different from the atoms in this proposal. Huston's atoms are allocated to ASes; ours are computed by backbone routers. Either approach has its advantages: allocated atoms are conceptually more easily established (not requiring computation), whereas computed atoms are likely to be more effective, in that they are computed based on the similarity of prefixes as observed by the routers. For instance, computed atoms allow prefixes originated by different ASes to be part of the same atom (such as atom A3 in Figures 2 and 3). In addition, computed atoms allow for greater transparency, since non-backbone routers are not involved in any way (Section 5).

However Huston's definition of atoms provides an interesting alternative that may be of use to us. In particular we can use the techniques in Sections 5.1 and 5.2 and apply them to allocated rather than computed atoms. So it should be possible to use allocated atoms as a `fallback' should it turn out that computed atoms are too expensive or unscalable.

To elaborate a little further on allocated atoms: rather than computing atoms in the backbone of the Internet, ASes throughout the Internet can be allocated atom ids (e.g. by IANA). ASes then announce and withdraw atom ids rather than prefixes in routing update messages. To propagate the mapping between atom ids and prefixes, BGP update messages that include a BGP community attribute RFC1997 can be used. The BGP community attribute contains the atom id, which applies to the prefixes carried by the update message. Such an approach removes the burden of atom computation from backbone routers. On the other hand, it is more drastic in that it requires all ASes in the Internet to cooperate.

7.2. Frank Kastenholz's Aggregates

In Kastenholz Frank Kastenholz introduces a new kind of aggregate. Kastenholz's aggregates are a significantly different concept from atoms. However, Frank Kastenholz is addressing similar issues. Also, like us, Kastenholz separates aggregate ids from aggregate contents, and performs routing computations on aggregate ids instead of prefixes. However, Kastenholz's approach does not remove knowledge of prefixes from any routers. In contrast, we remove prefixes from a subset of routers (the transit routers in Section 5.1), or at least from the forwarding tables (Section 5.2).

We also believe that our approach is somewhat less disruptive than Kastenholz's: we point to ways in which atoms can be applied effectively within the backbone (or part of the backbone) transparently (Sections 5.1 and 5.2).

Next: 8. Planning