Course Matters

1
Course Matters
2
Deadlines

• 11 Oct Survey Paper Due
• 18 Oct Paper Reviews Due

3
Reminder

• No lecture next week
• Make-up lecture
• 23rd October 2004, Saturday
• 1-3pm

4
Previously, on CS5248..
5
New Model IP Multicast
sender
receivers
6
Multicast
S
A
G
Router
B
Router
Router
Router
C
7
Multicast
S
A
Router
G
B
Router
Router
Router
G
C
8
Multicast
S
G
A
Router
B
Router
Router
G
Router
C
9
So, why cant we multicast?

• Who assign multicast address?
• Who pay for multicast traffic?
• How to inter-operate between protocols?
• How can we prevent DoS?

10
Application-Level Multicast
11
You are Here
Encoder
Decoder
Middlebox
Sender
Receiver
Network
12
Application-Level Multicast
S
A
A
Router
B
Router
Router
Router
C
13
Application-Level Multicast
S
B
C
A
Router
B
Router
Router
Router
C
14
Overlay Network
S
A
B
C
15
Penalty Delay
S
A
Router
B
Router
Router
Router
C
16
Penalty Network Resource
S
A
Router
B
Router
Router
Router
C
17
Link Stress
S
A
Router
B
Router
Router
Router
C
18
Questions

• How to construct overlay multicast tree?
• How to maintain overlay multicast tree?

19
A Case for End-System Multicast

• Y. Chu, S. Rao, S. Seshan, H. Zhang
• JSAC 2002

20
Naradas Idea

• Build a mesh, then build a tree

S
S
A
A
B
C
B
C
21
Why Build Mesh?
22
Desirable Property of Mesh

• Path between any two nodes must be good
• Cannot be too sparse or too dense

23
How to build Mesh?

• Node join
• Randomly choose some existing members as neighbour

S
A
B
C
24
How to maintain Mesh?

• Everybody knows everybody
• Each node maintains a table

25
How to update table?

• Refresh messages
• Exchange of tables

26
How to maintain Mesh?

• Node failure
• Probes if no refresh messages for a while

S
A
B
C
27
How to maintain Mesh?

• Mesh Partition
• Probes if no refresh messages for a while, add
  random edges if alive

S
A
B
C
28
How to Optimize Mesh?

• Mesh needs to periodically updated because
• nodes join and leave
• network condition changes
• partition repair add unneeded edges
• initial constructions are random

29
Adding a Link

• Node i periodically probe randomly selected
  members j
• Ask what if I add (i,j)?

30
Adding a Link
S
S
A
A
B
C
B
C
31
Removing a Link

• Harder to ask what if I remove link (i,j)?
• compute cost(i,j) instead number of nodes for
  which i uses j as next hop

32
cost(i,j)
cost(S,A) 2
S
A
B
C
33
cost(i,j)
cost(S,A) 3 cost(A,S) 1
S
E
A
D
B
C
34
Removing a link

• if max(cost(i,j), cost(j,i)) lt Threshold
• drop (i,j)
• (Threshold should depends on group size)

35
Naradas Idea

• Build a mesh, then build a tree

S
S
A
A
B
C
B
C
36
How to build tree?

• Modify DVMRP
• Cost definition
• Pick widest path
• Break ties by latency

37
Evaluation Bandwidth
38
Evaluation RTT
39
Evaluation Link Stress
40
Evaluation Resource Usage
41
Scalable Application Layer Multicast

• S. Banerjee, B. Bhattacharjee, and C. Kommareddy
• SIGCOMM 2002

42
Problem

• Narada does not scale
• State maintenance
• Message overhead

43
NICE

• NICE is scalable
• State maintenance
• Message overhead

44
Members
45
Clusters
46
Leader
47
Layer
48
Nodes per Cluster
k, 3k-1
49
Control Topology
50
Multicast Tree
51
Analysis
height
52
Analysis

• Control Message Overhead

53
Analysis

• Worst Case Control Message Overhead
• Average Case Control Message Overhead

54
Analysis

• Number of hops between 2 nodes

55
Analysis

• Maximum Degree of a Node

56
Multicast Tree (Improved)
57
Node Join
58
Other operations

• Node leave
• Node failure
• Cluster merge/split

59
Evaluation Control Overhead
60
Evaluation Link Stress
61
Evaluation Path Length
62
Previously, on CS5248..
63
Patching
Time
mcast
unicast
Client Request
64
Patching (Attempt 2)
Network
S
65
Patching (Attempt 2)
Network
S
66
Patching (Attempt 2)
Network
S
67
Patching (Attempt 2)
Network
S
68
Patching (Attempt 2)
Network
S
69
Patching (Attempt 2)
Network
S
70
Patching (Attempt 2)
Network
S
71
Patching (Attempt 2)
Network
S
72
Patching with Cache Proxy
Network
S
73
Patching with Cache Proxy
Network
S
74
P2Cast P2P Patching Scheme for VoD

• Y. Guo, K. Suh, J. Kurose, D. Towsley
• WWW 2003

75
ALM with Patching
76
P2Cast
77
New Session
78
Existing Session Patch
?
?
79
Node Join
join
80
Node Join
(measure B)
81
Node Join
82
Failure Recovery
X
83
Failure Recovery

• What if
• Patch server failed?
• Base server failed?