Experiential analysis of Internet AS-level structure

Yangyang Wangadvisor: Prof. Jianping WuNCR, Tsinghua University

outlines

• Motivation• Related work• analysis methods• Data source• Some results• Conclusion

motivation

• ASes are the basic units of Internet• Internet AS-level topology research can help:– Internet topology modeling– Network design planning– architecture design or optimizing for wide-area

distributed system

Related work

• Some related work (not all)– Jellyfish conceptual model (G. Siganos, JCN 2006)• Undirected graph• Degree-based

– BGP routing table tomography from Multiple Vantage Points (L. Subramanian INFOCOM’02)• Directed graph derived from AS_PATH from BGP

monitor

methods• Topology with AS relationship is a directed graph G

– Each vertex is AS– directed edge: connection between ASes – customer-provider, peer-peer, sibling-sibling

Provider

Customer

one directed edge represent a C2P relationship

Peer/Sibling

Peer/Sibling

P2P or S2S relationship is split into two inverse directed edges

methods

• Ranking algorithmsr = 1while (leaves(G) is not empty){

for each v of leaves(G)rank(v) = R;

remove leaves from G, get a new G;r = r + 1;

}for all the rest v in G

rank(v) = r;

• Case 1:• Leaves(G) are vertexes

without customers. It just considers the C2P hierarchy, ignore P2P and S2S.

• Case 2:• Leaves(G) are vertexes

without customers, peers and siblings.

Data source

• CAIDA inferred AS relationship dataset– http://as-rank.caida.org/data/

– Its raw data are from RouteViews project and IRR(Internet Routing Registry)

• Data in 03/03/2008-03/17/2008– as-rel.20080303.a0.01000.txt

as-rel.20080310.a0.01000.txtas-rel.20080317.a0.01000.txt

– Joined them into one data file, choose the inferred relationship with higher occurrence frequency as the final relationship for each link

layershierarchical layers of Case 1

24415 (87%)

2468 (9%)

584 (2%)

176 (1%) 202 (1%)

Outmost layer with very high number of AS

These middle layers include very little number of AS

Innermost layer

layershierarchical layers of Case 2

23767 (85%)

2014 (7%)

308 (1%)

54

1820 (7%)

bigger Innermost layer than Case 1

Less layers than Case 1

Outmost layer with very high number of AS

Other metrics

• We can examine other aspects:– the number of links in each layer itself– the number of cross links and included P2P links

from one layer to the other layers– average degree of the rest graph G after removing

layer n– link connection density of the rest graph G after

removing layer n, and defined as (E(G)* 2) / (V(G)* (V(G) – 1))

other metrics

layer 1 2 3 4 5 6 7 8 9 10 11(core) p2p link(to core) averagedegree

linksdensity

1 783 7621 5898 3146 2225 929 329 331 45 720 22309 830(85.1%) 4.17 0.0001

2 357 1067 527 309 115 43 32 25 36 4755 860(89.9%) 7.9 0.0022

3 114 280 117 39 18 8 8 13 2019 591(89.5%) 12.48 0.0115

4 55 109 20 18 9 1 9 966 417(87.1%) 16.58 0.0332

5 25 29 5 9 1 13 578 289(90.7%) 18.27 0.0565

6 6 10 2 2 5 264 129(97.7%) 18.47 0.0745

7 2 4 2 1 151 83(97.6%) 17.71 0.0784

8 1 2 3 94 66(97.0%) 16.97 0.0782

9 3 6 29 9(88.9%) 16.43 0.0775

10 2 93 62(100%) 16.38 0.0788

11 1617 770(100%) 16.01 0.0797

cross layer links table of Case 1

many of cross links

few of cross links

plenty of cross links approximate increasing

other metrics

layer 1 2 3 4 5 6 7(core) p2p link (to core) averagedegree

linksdensity

1 645 5477 2424 676 79 1 32364 2(100%) 4.17 0.0001

2 226 488 115 10 0 3839 8(100%) 7.95 0.0019

3 30 66 5 0 800 2(100%) 11.00 0.005

4 8 3 0 173 0 11.84 0.0063

5 0 0 9 0 11.99 0.0066

6 0 15 10(100%) 12.00 0.0066

7 10911 4093(100%) 11.99 0.0066

cross layer links table of Case 2

many of cross links

few of cross links

plenty of cross links

degrees vs. layer rank

Case 2Case 1

we could see that vertexes with high degree may be in lower hierarchy rank

conclusion

• conceptual conclusions– there are a small core (less than 10%), large

margin AS (more than 80%), and middle AS band (about 10%)

– remove margin AS, the rest network size is not very small (about 10%) and connections are very complex

– although outer AS have most connections to the core, there are a few connections to middle AS zone, which reduce the regional routing path.

Problems and future work• Problems:– inaccurate AS relationship

• Missing P2P links– incomplete topology data

• Limited BGP monitor• Measurement bias

• Future work– other method of charactering structure pattern– What’s the size of the core as Internet expands– What would look like the topology structure in the

future 10- 20 years according current principles

Thanks !