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CIS679: Anycast

Review of Last lecture Anycast

Review of Last Lecture

H.323

Anycast

Unicast, multicast and anycast

Usage of Anycast

Providing Service transparency DNS server, and mirrored Web site

Improving network performance load balance at application and network layers

An Example for Ancast Usage

R13R12

R9

R7

R11R10

R8

R1 R2

R4

R5

R3

R6

1 mbs

1 mbs 1 mbs

1 mbs1 mbs

3 mbs

A traffic flow with SP-To-Core method

core

Anycast at Different Layers

Network-layer anycast Anycast address Anycast membership management Anycast routing

Application-layer anycast

Anycast Address

Shares with unicast Advantage: compatible to unicast Disadvantage: too like unicast, some benefit of

anycast lost

Separate from unicast, just like multicast Advantage: easy to make full use of anycast

semantics Disadvantage: difficult to deploy

Anycast Membership Management

Similar to multicast -- IGMP But, there is more freedom

Anycast RoutingAnycast Routing

Single-path Routing

The path from the source to the destination is time invariant.

Multi-path Routing The traffic from the source to the destination is split into different paths.

Multi-Path Routing for Anycast Messages

Two issues Loop free routing How to select multi-path?

Loop in Anycast Loop in Anycast RoutingRouting

Dest Dist hopA, H15

A, H16

A, H17

A, H18

10 R7

9 R12

8 R13

3 R14

Routing table at R10

Dest Dist hopA, H15

A, H16

A, H17

A, H18

8 R9

9 R9

10 R10

5 R10

Routing table at R7

Dest Dist hopA, H15

A, H16

A, H17

A, H18

5 R11

6 R12

13 R7

8 R7

Routing table at R9

Dest Dist hopA, H15

A, H16

A, H17

A, H18

7 R9

4 R16

13 R10

8 R10


H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}HiRouter HostRi

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

Link with distance 1 Link in a loop2

Loop-free Routing

Ordered routing A router with a higher order can send anycast message

to a lower order router.

Methods to order the routers SSPF method MIN_D method SBT method CBT method

The SSPF Method

SSP order: X>SSPY if Y is the next hop of X on Pssp(X, G(A)).

An anycast packet is routed to the nearest member of the anycast group.

The SSPF Method

*

*

Dest Dist hopA, H15

A, H16

A, H17

A, H18

2 R11

9 R9

16 R9

11 R2


Dest Dist hopA, H15

A, H16

A, H17

A, H18

7 R5

12 R5

20 R5

15 R5

Routing table at R1

Dest Dist hopA, H15

A, H16

A, H17

A, H18

6 R11

12 R2

19 R12

14 R2

Routing table at R5

Dest Dist hopA, H15

A, H16

A, H17

A, H18

1 H15

10 R11

17 R11

12 R11


*

*

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}HiRi Router Host

Link with distance 1Link on DBTs

2 Congested link 1

The MIN-D Method

Function min_d()

MIN_D order X >MIN_DY if min_d(X, A) > min_d(Y, A).

An anycast packet is routed to the nearer member of the anycast group.

))).,(((min),(min_)(

HXPDAXd SPAGH

The MIN-D Method

Dest Dist hopA, H15

A, H16

A, H17

A, H18

10 R7

9 R12

8 R13

3 R14


Dest Dist hopA, H15

A, H16

A, H17

A, H18

6 R9

7 R9

14 R10

9 R10

Routing table at R6

Dest Dist hopA, H15

A, H16

A, H17

A, H18

5 R11

6 R12

13 R7

8 R7

Routing table at R9

Dest Dist hopA, H15

A, H16

A, H17

A, H18

7 R9

4 R16

13 R10

8 R10


* **

**

*

*

*

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

Link with distance 1 Link on a general graph 2

Congested link 1

7 7 6 6

6 6 5 5

1

5 3

4 22 4

1 11

H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}HiRi Router with MIN-D Host2

The SBT Method

SBT order: X>SBTY if X is the father of Y on the source-based tree of

Source S

An anycast packet is routed along the source-based tree rooted at the source of the packet.

The SBT Method

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

Link with distance 1Link on a SBT tree rooted at R3

2

Ri Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}Hi Host

Dest Dist hopA, H15

A, H16

A, H17

A, H18

6 R9

7 R9

14 R10

9 R10

Routing table at R6

*

Dest Dist hopA, H15

A, H16

A, H17

A, H18

5 R11

6 R12

13 R7

8 R7

Routing table at R9

*

Dest Dist hopA, H15

A, H16

A, H17

A, H18

8 R9

9 R9

10 R10

5 R10

Routing table at R7

Dest Dist hopA, H15

A, H16

A, H17

A, H18

9 R6

10 R6

11 R7

6 R7

Routing table at R3

*

*

*

**

* *

*

The CBT Method

CBT order: X>CBTY if X is the father of Y on the core-based tree.

For an anycast packet: at the on-CBT router, it is routed following CBT order. at the off-CBT router, it is routed following SSP order

The CBT Method

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

Ri Router H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}Hi Host

Dest Dist hopA, H15

A, H16

A, H17

A, H18

10 R7

9 R12

8 R13

3 R14


Dest Dist hopA, H15

A, H16

A, H17

A, H18

8 R9

9 R9

10 R10

5 R10

Routing table at R7

Dest Dist hopA, H15

A, H16

A, H17

A, H18

5 R11

6 R12

13 R7

8 R7

Routing table at R9

Dest Dist hopA, H15

A, H16

A, H17

A, H18

7 R9

4 R16

13 R10

8 R10


**

*

*

**

*

*

*

Link with distance 1Link on a CBT tree rooted at R7

2Link on the truncated DBTs

2

Summary of Router-ordering Methods

The number of loop-free pathsSSPF < MIN_D < SBT = CBT

Overhead in terms of the memory storageSSPF < MIN_D < CBT << SBT

Multiple Path Selection

Weight Random Selection (WRS) A path with high weight has higher probability to

be selected than the path with low weight. A rule of thumb

the weight should be inversely proportionally to the distance of the route, i.e, W~ 1/D

K

j

r

j

r

ii

D

DW

1

)1

(

)1

(

• when r = 0, Wi = 1/K• when r = , Wi = 1/Di if Di < Dj for any j, o.w. 0

Weight Assignment

Consider R12 with r=1 W15 = 0. 24, W16 = 0.42, W17 = 0.13, and W18 = 0.21

Dest Dist hopA, H15

A, H16

A, H17

A, H18

10 R7

9 R12

8 R13

3 R14


Dest Dist hopA, H15

A, H16

A, H17

A, H18

6 R9

7 R9

14 R10

9 R10

Routing table at R6

Dest Dist hopA, H15

A, H16

A, H17

A, H18

5 R11

6 R12

13 R7

8 R7

Routing table at R9

Dest Dist hopA, H15

A, H16

A, H17

A, H18

7 R9

4 R16

13 R10

8 R10


* **

**

*

*

*

1

1 1 11

H1

1H2

1

H6

1H7

1

H8

1

H15

1

H4

1

H17

1H18

1

H5

1

4

2

1

3

6

1

32

2

7

32

16

3 3

41

4

R1 R2 R3 R4

R5 R6 R7 R8

R9 R10

R14R13R12R11

R15 H16

1R16 R17 R18

5

H3

Link with distance 1 Link on a general graph 2

7 7 6 6

6 6 5 5

1

5 3

4 22 4

1 11

H1~H8 Anycast packet sources G(A) = {H15, H16, H17, H18}HiRi Router with MIN-D Host2

Performance Evaluation

Metrics: the average end-to-end delay Evaluated systems: <α, β, γ>

α {SSP, MIN_D, SBT, CBT} β {fixed, adaptive} γ {independent, flow}

Network: ARPANET, one group with 5 members

Traffic: Poisson

(a) <*, Fixed, Non-Flow>

0.00 0.50 1.00 1.50 2.00Throughput

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040SSPGOCBTSBTDOR

0.00 0.50 1.00 1.50 2.00Throughput

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040SSPMIN-DCBTSBTDOR

(b) <*, Fixed, Flow>

0.00 0.50 1.00 1.50 2.00Throughput

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035


0.00 0.50 1.00 1.50 2.00

Throughput

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035


(c) <*, Adaptive, Non-Flow> (d) <*, Adaptive, Flow>

Evaluation Results

Conclusion

Anycast motivation Anycast address Anycast membership management Anycast routing

Multi-routing • loop-free routing methods• multiple path selection