overlay multicast mechanism

Overlay Multicast Mechanism

Student : Jia-Hui Huang

Adviser : Kai-Wei Ke

Date : 2006/5/9

2

Outline

Introduction Topology-Aware Grouping End system multicast Simulation Summary

3

Introduction

IP multicast Drawback Require router to maintain per-group state Reliability, congestion control, flow control more

difficulty Overlay multicast

Build an overlay multicast tree on top IP layer Unicast data along tree links Application level multicast

4

Overlay multicast mechanism

Topology-Aware Grouping (TAG) End system multicast (ESM)

Narada

5

Outline


6

TAG(1/2)

Exploits underlying network topology information

Use path overlap among member to reduces Delay Link Stress

TAG node maintain IP and paths for parent and children – Family table (FT)

7

TAG(2/2)

Definition A path from node A to node B

The spath of A where S is the root of the tree

Length of a path or is the number of routers in the path

if is a prefix of where s is the root of the tree

( , )P A B

( , )P S A

P ( )len P

A B ( , )P S A ( , )P S B

8

Complete path matching(1/2)

Like longest prefix match Algorithm consider three mutually exclusive

conditions Select a node A such that A is child of C Select children of C No child of C satisfying 1 or 2

N : new member

C : the node being examined

A N

iA iN A

9

Complete path matching(2/2)

Recursive algorithm until condition 2 or 3 is meet

Tree management Member join Member leave Fault resilience

Parent and children periodically exchange messages Child failure : discards the child from it’s FT Parent failure : rejoin

10

Outline


11

ESM

Shift multicast feature to end system Group membership Multicast routing Packet duplication

Using a self-organizing and fully distributed algorithm Narada algorithm

Two steps of Narada algorithm Construct a mesh Construct per-source spanning tree for mesh

12

ESM Concept

Link Stress (Si): number of identical copies of a packet carried by a physical link

Distance (di) Resource usage

l

lii sd

1

*

A

B D

C

R1 R125

1

2 1

1

A

B D

C27

27

3 2

28

28

IP Multicast Resource Usage : 30IP Unicast Resource Usage : 57End System Multicast Resource Usage : 32

Complete virtual graph

13

Narada Design (1/2)

objectives of Narada algorithm Self-organizing Overlay efficiency Self-improving

Narada algorithm Group Management Mesh Performance Data delivery

14

Narada Design (2/2)

Two steps of algorithm Group management functions are

abstracted out and handled at the mesh

Distributed heuristics for repairing mesh partition

We may leverage standard routing algorithms for construction of data delivery trees

Mesh

Tree

15

Group management (1/5)

Distributed manage membership Every member maintain a list of other members in

the group List need update when join, leave or fail

Refresh message mechanism Each member periodically generate a refresh

message with sequence number Dissemination refresh message along the mesh

16


Member i keeps track of the information for every other member k in the group Member address k Last sequence number Time of first receive

Reduce overhead of refresh message Each member periodically exchange its knowledge of

membership with neighbors

kiS

kiS

17


Three operation of group management Member join Member leave and failure Repairing mesh partitions

Member join process It assume can get a some member list Random select member from list to send join message The join message request added as a neighbor of that

member Repeat process until successful join the group Refresh message mechanism to obtain group info.

18


Member leave and failure Member must notifies its neighbors before leave Leave information will propagated to the rest of group

members Abrupt

Detected by neighbors when stop receive refresh Propagate information to other members

Ex of failure if node c fail

E

F

B A

D

G

C

19


Repairing mesh partitions Member failure may cause partition Each member maintain a queue that stopped rece

ive refresh message for at least time Periodically run a scheduling algorithm to probe a

nd delete member from head of queue

mT

20

Mesh performance (1/3)

The constructed mesh can be suboptimal because Random selection neighbor when join Link add in partition repair my not useful in long

time Underlying network conditions may vary

Using utility mechanism to add or drop link dynamically and improve quality

21


Utility function depends on the what kind of performance metric specific Example latency and bandwidth ( conferencing

application ) Addition of links

Every member periodically probe some random members that is not neighbor

And evaluate the utility of adding a link to this member

Determine if add link by a given threshold

22


Dropping of links Every member periodically computes the cost of

its link to every neighbor using the cost algorithm The cost of a link between I and j in I’s perception

is the number of group members for which I use j as next hop

Picks the lowest cost link and drops it if it falls below threshold

23

Data delivery

The per-source trees constructed from the reverse shortest path between each recipient and source

24

Outline


25

Simulation (1/2)

Properties of simulation topology Power-law

Larger number of low-degree routers than high-degree routers

Small-world Avg. shortest distance between two randomly chosen

nodes is approximately six hops

26

Simulation (2/2)

Property of constructed overlay tree High-degree high-bandwidth router more likely

traversed by links near the source Simulation metrics

Number of hops vs. overlay tree level Relative delay penalty (RDP) Longest Latency Mean Bandwidth

27

Number of hops vs. overlay tree level

Number of hops decreases as the host level increases

28

Relative delay penalty (RDP)

ESM < MDDBST < TAG

29

Longest Latency

Latency & RDP for ESM decrease as more hosts join Lower latency paths become availableESM > TAG > MDDBST

30

Mean Bandwidth

Trade-off between latency and bottleneck bandwidthMDDBST > TAG > ESM

31

Outline


32

Summary

Both delay and number of hops between parent and child decrease as the level increase

Balance the trade-off between delay and bandwidth

33

Reference

Yang-hua Chu, Sanjay G. Rao, Srinivasan Seashan, and Hui Zhang, “A Case for End System Multicast,” IEEE Journal On Selected Areas In Communications, VOL. 20 ISSUE 8, Oct. 2002, pp. 1456-1471

Sherlia Y. Shi, Jonathan S. Turner and Marcel Waldvogel, “Dimensioning Server Access Bandwidth and Multicast Routing in Overlay Networks,” Proceedings of NOSSDAV 2001.

Minseok Kwon and Sonia Fahmy, “Topology-Aware Overlay Networks for Group Communication,” Proceedings of NOSSDAV'02, May 2002.

Minseok Kwon and Sonia Fahmy, “Characterizing Overlay Multicast Networks,” IEEE International Conference on Network Protocols, pp. 61

34

Outline

Introduction Dimensioning server multicast routing Topology-Aware Grouping End system multicast Simulation Summary

35

Dimensioning server multicast routing(1/2) Use AMcast network architecture

Deploy application servers on the networks Spawn a start topology from each server to its end

users End users send/receive exactly one copy of

packet Work shifted from source to all servers

Design routing algorithms from two objectives

36

Dimensioning server multicast routing(2/2)

Delay Optimization Minimum diameter, degree-bounded spanning

tree (MDDBST) Load balancing

Bounded diameter, residual-balanced spanning tree (BDRBST)

Two objectives are orthogonal

37

MDDBST(1/4)

Definition

given

G=(V,E) : undirected complete graph

: degree bound

: cost for edge e

Find

A spanning tree T of G for each and

degree of v satisfies

diameter (the cost of the longest simple path) of T

is minimized

max ( )d v

( )c e

v Tmax( ) ( )Td v d v

( )dia T

38

MDDBST(2/4)

Start from single node

Select smallest node

Add node u to Tree T

Update nodes in tree T

Update nodes not in tree T

All node in tree T

All node has corresponding

tree

complete

A

A

N

Y

N

Y

Longest path of u to any other nodes in T

( )u

39

MDDBST(3/4)

max ( ) 3d v

{ }W A

( ) 0A A

B E

DC

12

9

8

3

764

5 10

A

B C D E( ) 2B ( ) 1E ( ) 7D ( ) 6C

( ) 1A

A

B C D

E

( ) 4B

( ) 1E

( ) 9D ( ) 10C

A

B

E

DC

{{ , }}L E A{ , }W A E { , , }W A E B {{ , },{ , }}L E A B A

( ) 2A

( ) 10C ( ) 9D

( ) 4B

( ) 4E

40

MDDBST(4/4)

( ) 6A

( ) 9E

( ) 4B

A

B

E

DC( ) 10C

( ) 9D

{ , , , }W A E B C {{ , },{ , },{ , }}L E A B A C B

( ) 7A

( ) 10E

( ) 5B

A

B

E

DC( ) 10C

( ) 9D

{ , , , , }W A E B C D

{{ , },{ , },{ , },{ , }}L E A B A C B D B

4

1

109

41

BDRBST(1/3) Definition given G=(V,E) : undirected complete graph : degree bound : cost for edge e B : cost Bound Find A spanning tree T of G for each and degree of v satisfies diameter (the cost of the longest simple path) of T

< B and maximize (residual bandwidth)

max ( )d v

( )c e

v Tmax( ) ( )Td v d v

( )dia Tmaxmin( ( ) ( ))Td v d v

42

BDRBST(2/3)

Introduce balance factor M Algorithm similar MDDBST Main difference

Select a set of M smallest nodes Select the largest residual bandwidth (smallest

degree) node as parent node Special cases

M=1 : algorithm same as MDDBST M= # of servers : only considers load balancing

43

BDRBST(3/3)

Increase system capacity by increase end-to-end delay

Small values of M provide good load balance while still meeting the diameter bound

44

AMcast architecture

45

MDDBST algorithm

46

Family table (FT)

FT

Parent <IP(A),P(S,A)>

Children <IP(Bi), P(S,Bi)>

…..

.

47

Topology aware definition

S

R1

D1

D5D3

D4

D2 R5

R3

R2

R4

Path from S to D5 ( spath of D5 )

( , 5) 1, 2, 4P S D R R R

( ( , 5)) 3len P S D

1 5D D

48

Path match condition

S

C

A

N

Path match

S

C

A1 A2 A3

S

C

A1 A2 A3

N

Path match

S

C

A2A1

S

C

A2A1N

Path match

Condition 1

Condition 3Condition 2

49

Complete path match algorithm

50

CPM Member join

Root

Member1

Member2

Path Matching

New Member

Join

Request/Reply

Request/Reply

Req

uest

/Rep

ly

…..

CPM Join process

S

R1

R2

R4

R3

D5

D2 D3

D4

D1

FT

D1 : (R1)FT

D2 : (R1,R2,R4)

FT

D3 : (R1,R2,R4)

FT

D4 : (R1,R2)

FT

D2 : (R1,R2,R4)

FT

D2 : (R1,R2,R4)

D5 : (R1,R2,R3)

51

CPM Member leave

Send LEAVE message Parent remove entry Parent add entry

S

R1

R2

R4

R3

D5

D2 D3

D4

D1

FT

D1 : (R1)

FT

D3 : (R1,R2,R4)

FT

D4 : (R1,R2)

FT

D2 : (R1,R2,R4)

D5 : (R1,R2,R3)

FT

D2 : (R1,R2,R4)

D5 : (R1,R2,R3)

52

Partial path matching process

S

R1

R2

R4

R3

D2

D3

D1

R5

R6

FT

D1 : (R1,R2)

D2 : (R1,R3,R4)

Bwthresh = 100kbps

D1-D3 : 300kbps

D2-D3 : 50kbps

S

R1

R2

R4

R3

D2

D3

D1

R5

R6

FT

D2 : (R1,R3,R4)

D4 : (R1,R3,R7)

D5 : (R1,R3,R2)

R7

D4

D5

FT

D1 : (R1)

FT

D3 : (R1,R3,R5,R6)

FT

D2 : (R1,R3,R4)

D4 : (R1,R3,R7)

Bwthresh = 100kbps

D1-D3 : 50kbps

D2-D3 : 600kbps

D4-D3 : 80kbps

Join process Leave process

53

Scheduling algorithm

Time exceed T

According probability

54

Utility function

Latency as metric

55

Addition of links

Berk1

Stan2CMU

Gatech1

Stan1

Gatech2

Probe

Berk1

Stan2CMU

Gatech1

Stan1

Gatech2Probe

Delay improves to Stan1, CMU

but marginally.

Do not add link!

Delay improves to CMU, Gatech1

and significantly.

Add link!

56

Cost algorithm

57

Dropping of links

Gatech1Berk1

Stan2 Stan1

Gatech2

Gatech1Berk1

Stan2CMU

Stan1

Gatech2

Used by Berk1 to reach only Gatech2 and vice versa: Drop!!

overlay multicast mechanism

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