[e2e] Narada: what does the "refresh message" mean?
sds at dcs.gla.ac.uk
Sun Apr 18 08:52:51 PDT 2010
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> Now, I have a question about the refresh message mentioned in the paper "A Case
> for End System Multicast" ------ what is the content of the message? only the
> sequence number or the list of entry that represent the group membership or both
> Several places in the paper metioning the notion "refresh message" which I'm
> confused of are: 1) paragraph two of section III-A : "To handle this, we require
> that each member periodically generate a refresh message with monotonically
> increasing sequence number, which is disseminated along the mesh." ------ I
> think it refer to a message containing only sequence number here 2) figure 3.
> and its description: "Actions taken by a member i on receiving a refresh message
> from member j." ------ I think it refer to a message containing a list
> representing the group member ship here. Seems contradictory in these places, so
> what does "refresh message" really mean?
It's not contradictory. The paragraph in S.III-A simply doesn't describe the full contents of a packet.
- Every group member periodically generates a message containing it's identity (IP address, perhaps), and a counter.
- Each peer periodically sends a list of origin:counter pairs to its neighbours.
It doesn't take much of a leap for each peer to issue one message regularly which satisfies the algorithm.
Remember that although the mesh is not fully connected, each peer maintains state referring to all other group members. So while refresh messages are exchanged between /neighbours/, the messages may contain information about the whole group.
> by the way, does any one have an implementation of narada?
I couldn't find any when I looked a few years ago. Though I did work on a link-state variant of Narada, called Orta, and you should still be able to pull the source code for that from here: http://svn.sdstrowes.co.uk/
The University of Glasgow, charity number SC004401
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