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The Ordered Core Based Tree protocol
(OCBT) is a shared-tree, loop-free multicast routing protocol that I developed
after showing that Tony Ballardie's original Core Based Tree (CBT) protocol
did not work correctly. Under common circumstances, CBT would not properly
form the multicast tree; under less common ones the multicast tree could
develop undetected loops, which would be disastrous in a shared multicast
tree. |
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Besides correcting the deficiencies
in the original CBT, OCBT extends the single core of CBT to allow multiple
cores, which provide robustness and flexibility in configuration, as well
as continued correct operation in the presence of network paritions. The
latest versions of CBT have incorporated some changes first described by
OCBT, but still does not use multiple cores; thus CBT is still subject
to the effects of network partitions and the failure of the single core. |
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There are three publications available
describing OCBT. The first is my master's thesis, which details the problems
with CBT, describes OCBT, and provides a complete proof and pseudo-code
for the protocol along with simulation results comparing OCBT and CBT.
The second is my paper published in the proceedings of INFOCOM '97, which
briefly covers the same topics, updating the pseudo-code but omitting the
proof of correctness. The third is a submission to Transactions on Networking
which adds mechanisms to construct multicast trees in the face of network
partitions and proves the correctness of protocol and the added mechanism. |
thesis
infocom
ton submission |
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Extending OCBT to the inter-domain case, we have developed
HIP, a hierarchical multicast routing scheme that uses OCBT to route between
heterogeneous multicast routing domains. HIP uses the underlying unicast
routing protocol and is therefor suitable for wide scale use with BGP.
The paper describing HIP appeared in the proceedings of PODC '98, and is
available from the link at the right. A version of this paper has also
been selected to appear in Computer Communications. I will make a link
available when the fraft is finished. |
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We have also developed a secure version of OCBT and
HIP called Keyed HIP (KHIP) that provides not only an efficient mechanism
for distributing multicast keys and changing them as necessary, but also
limits access to the multicast routing tree to authorized members, preventing
unauthorized members from sending to or receiving even encrypted data from
the multicast session. KHIP is to appear in the proceedings of Sigcomm99. |
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