Information Technology Reference
In-Depth Information
Rendezvous point
UMRP
Host
DM
Unicast tunnel
Designated member
DM
DM
Multicast router
Host
Host
IP multicast Island
Normal member
Figure 1.11
The architecture of universal multicast. (From Zhang, B., Wang, W., Jamin, S., Massey, D., and
Zhang, L., Computer Networks, 50, April 2006. With permission.)
In HMTP, an IP-multicast island is defined as a network of any size
that supports IP multicast. One member host in an island is elected as the
Designated Member (DM) for that island. Different islands are connected by
user datagram protocol (UDP) tunnels. In HMTP, only DMs participate in
tree construction and maintenance. Data communication among DMs use
ALM, and, within each IP-multicast island, it takes advantage of IP-multicast.
The HMTP is a protocol to build a group-shared tree where multisenders
share this group-shared tree for bulk data transfer. UM employs HTMP for
inter-island routing and the Host Group Management Protocol (HGMP) for
intra-island multicasting. Disadvantages of hybrid multicasting include the
complexity of the system and performance variation due to the dynamic
nature of the end host.
1.3 Content Lookup in Peer-to-Peer Networks
As previously mentioned, P2P networks can be used to share the server load,
and one of the methods is to distribute the content to peers. To do so, we need
to have a protocol to distribute that content, and a method to locate the con-
tent afterward. In this section, we first introduce structured P2P networks,
in which pieces of content are distributed and searched by using a DHT.
We also introduce some systems that employ structured P2P networks as
their content lookup substrate. In addition to the content discovery, we will
see that in a structured P2P network, the route to the content can also be
employed to form a multicast tree for content delivery. After that, we briefly
introduce unstructured P2P networks and a system that uses an unstruc-
tured P2P network as its content lookup substrate.
 
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