Dear all, Matthieu and I are considering changing the encoding of source-specific updates in an incompatible manner. We haven't decided anything yet, here's a summary of our thinking.
The current encoding of source-specific updates is described in https://tools.ietf.org/html/draft-boutier-babel-source-specific-01 In short, a source-specific update is carried by a new TLV type, which is silently ignored by non-source-specific implementations. There are two other new TLV types, for requests for source-specific routes. Note that source-specific updates cannot be encoded as an ordinary update with a sub-TLV for the source, since Babel lacks a mandatory bit: the sub-TLV would be discarded by non-source-specific routers, and the update would be mis-interpreted, leading to routing pathologies. Now Babel uses a single Update TLV for both IPv4 and IPv6; IPv4 is distinguished from IPv6 by the AE, which is a one-octet field with values 1 for IPv4 and 2 for IPv6. See Section 4.1.3 of RFC 6126. Unknown TLVs are silently discarded according to RFC 6126 (although Matthieu has noted a bug in the implementation with this). The idea would be to encode source-specific updates using the existing Update TLV, with two new AE values for v4 source-specific and v6 source-specific. This avoids the need for three new TLVs, and significantly simplifies the packet parser. There are some minor complications; the structure of the Update TLV changes, but only for the new AEs (so compatibility is preserved). Additionally, there are some complications with address compression (do we organise a leak of information between different AEs, or do we make compression completely independent? the latter is simpler and cleaner, so I tend to favour it, while the former gives slightly better compression). Opinions? -- Juliusz _______________________________________________ Babel-users mailing list [email protected] http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/babel-users
