Multicast Flashcards
What is ASM, and where is it applied?
Any-Source Multicast:
– Movie-distribution, Pay-TV
– Software updates, multicast file transfer
– Video conference
Why is ASM receiver based?
New group members attach to the closest branch of the multicast tree: Very scallable.
What is needed for the IPv4 multicast model?
IPv4 + IGMP
What is needed for the IPv6 multicast model?
IPv6 integrates Multi Listener Discovery (MLD)
In IGMP, who sends the membership reports and to whom?
The Hosts (receivers) to routers.
In IGMP, who initiates a general membership query?
Any multicast-capable router.
Explain Dense-mode ASM
All multicasts packets are forwarded to and by all multicast routers. If packet from interfacei is received from source S, and i is in the shortest path from S, then packets fromi are forwarded. Else the packet is refuced.
This is called Reverse path forwarding (RPF)
If pruning is included, If there are no group members in a subtree, this subtree is cut off by sending a prune message to the previous hop router.
Explain Sparse-Mode ASM
First, build a tree from a core/center. The recipients send a join/leave message to that core. During multicast, a source sends a message to the core, who distributes it to all group members.
What is the disadvantage for general ASM?
Connection state scalability:
– Entries for each multicast group
– Huge multicast tables in backbone
What is the disadvantage for sparse-mode ASM?
Source advertisement mechanism scalability: core node needs to
be globally advertised
What is the disadvantage of dense-mode ASM?
Source advertisement mechanism scalability: flood and prune mechanism.
What is the selection strategy for BitTorrent Up/Download?
Rarest piece/chunk first
What is the balance between up and download speed in Bittorrent?
Fair = equal
