cis679: anycast
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
Routing table at R12
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
Routing table at R11
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
Routing table at R15
*
*
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
Routing table at R10
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
Routing table at R12
* **
**
*
*
*
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
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
Routing table at R12
**
*
*
**
*
*
*
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
Routing table at R10
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
Routing table at R12
* **
**
*
*
*
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
0.040SSPMIN-DCBTSBTDOR
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
0.040SSPMIN-DCBTSBTDOR
(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