Commit 21148a84 authored by Juliusz Chroboczek's avatar Juliusz Chroboczek

Tweaks to the protocol spec.

parent 6fa22d7b
......@@ -38,22 +38,23 @@ will interoperate reliably.
2. Protocol operation
Every Babel speaker has a router id, which is an arbitrary string of 16
bytes that MUST be unique across the routing domain. A simple choice is to
use one of the speaker's IPv6 addresses as the router id; the encoding of
some messages is more efficient when this is indeed the case.
bytes that MUST be unique across the routing domain. A natural choice is
to use one of the speaker's global IPv6 addresses as the router id; the
encoding of some messages is slightly more efficient when this is indeed
the case.
2.1 Message emission and reception
Babel speakers exchange Babel protocol messages. One or more Babel
messages are appended to form a Babel packet, which is sent as a UDP
datagram.
datagram over IPv6.
The source address of a Babel packet is always a link-local unicast
The source address of a Babel packet is always a link-local unicast IPv6
address; a Babel speaker MUST silently discard any packets whose source
address is not a unicast link-local address. Babel packets may be sent to
a well-known link-local multicast address (this is the usual case) or
a link-local unicast address.
to a link-local unicast address.
With the exception of Hello messages, all Babel messages can be sent either
in unicast and multicast packets, and their semantics does not depend on
......@@ -246,17 +247,21 @@ source table entry is updated according to the following rules:
- if metric' is infinite, then nothing is done;
- if seqno' > seqno, then seqno := seqno', metric := metric', and the
garbage collection timer for the entry is reset ;
garbage collection timer for the entry is reset;
- if seqno' = seqno and metric < metric', then seqno := seqno',
metric := metric', and the garbage collection timer for the entry is
reset;
- otherwise, the garbage collection timer for the entry is reset.
An entry in the table of sources is purged when its garbage collection
timer hasn't been reset for 200 seconds.
An update (id, prefix, seqno', metric') received from a neighbouring node
is feasible when either metric' is infinite, or (seqno', metric') is
strictly smaller than the reference distance of (id, prefix). In other
words, an update (id, prefix, seqno', metric') is feasible when one of the
following conditions is true:
(Section 2.3.2) is feasible when either metric' is infinite, or
(seqno', metric') is strictly smaller than the reference distance of (id,
prefix). In other words, an update (id, prefix, seqno', metric') is
feasible when one of the following conditions is true:
- no entry exists in the source table for (id, prefix); or
- metric' is infinite; or
......
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