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GIRO: Geographically Informed Inter-domain

Routing

Ricardo Oliveira, Mohit Lad, Beichuan Zhang, Lixia Zhang

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Internet and Autonomous Systems

AT&TSprint

Verizon

•Autonomous System: a set of routers or networks under the same administration

•Border routers exchange routing updates via the Border Gateway Protocol (BGP)

•Reachability announced through the form of prefixes, i.e. chunks of IP addresses

24.143.92/24

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?ra

rb

rc

Prefix P

1. Policy: costumers > peers > providers

2. Lowest AS hop count

3. …

What problem we are solving

• BGP route selection: how to pick the best one?

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One Example

• Router A sends packets to prefix P• A has two ways to reach P:

• Both AS 577 and AS 3561 are peer links

• Following "lowest AS hop" rule: A sends packets to AS 577

P: AS 3561, AS 577

P: AS 577

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Suboptimal route selection !

AS3561AS577

AS6461

Seattle, WA

Palo Alto, CA

Chicago, IL

A

BGP path (~ 3600 miles)Shorter path (~700 miles)

P

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GIRO Design Goals

Geographical information

1. Improve data delivery performance within established routing policies

2. Improve routing scalability by reducing the global routing table size

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GIRO Design Approach

• Adding geographic information into– Routers– BGP routes– IP address

• When everything else being equal: select path with shortest distance

• Aggregate route announcements by ASes and locations

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Adding geographic information

• Configure each BGP router with geographic location informaiton

• Define a new BGP "location" attribute to be associated with each AS hop e.g. using BGP communities

• Enables each router to calculate the total path length

xinC, yinC

C

B

A

xoutB, youtB

xinB, yinB

xoutA, youtA

xorigin, yorigin

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GIRO Address Scheme

ASN geolocation SID Subnet and host

External component(G-prefix)

Internal componen

t• Including ASN upfront in the address ensures that pkts are routedprimarily based on policies

• Geolocation information serves as secondary hint

• Traffic slice (SID) divides the incoming traffic to the G-prefix, e.g.one SID per provider

• The internal component is not announced to other networks; it’s used to route pkts inside the origin network

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D

Prefix Aggregation in GIRO

A

E

C

B

Los Angeles,CA

San Francisco,CA

Chicago,IL

Toronto,CANNew York,NY

SID=0

SID=1

G-prefix ASPATH

B.US.CA A B

B.US.IL A D B

B. CAN A D B

C.US.NY.NewYork.0 A C

C.US.NY.NewYork.1 A D C

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Egress Point Selection

late

R1

R6

R2 R3

R5

R7

R0

100|12A

B

50|530|3

30|390|10early

shortest-path

200 0 0

40|5

Geographic distanceIGP weight

late-exit

R4

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GIRO Decision Process

Step Description

1. Highest LocalPref

2. Shortest geographic distance w/ resolution

3. Lowest AS hop count

4. Lowest origin type

5. Early exit (take route of shortest IGP distance)Late-exit (take lowest MED route)Shortest-path (take routes of shortest geographic distance)

6. .......

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• 70% of paths areshorter using GIRO compared to BGP

• 20% of paths arereduced by more than 40%

Evaluation: Inter-domain route selection• Used a RocketFuel PoP level topology with 668

inter-AS links and 67 ISPs• For simulations used =124 miles (equivalent of one sec. delay on fiber)

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Evaluation: GIRO aggregation

• Extracted prefixes from BGP tables from Jan 2007-March 2007

• Mapped each prefix to a geographical location using Maxmind Geolite– Found mapping for ~80% of prefixes

(~196K)

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GIRO Aggregation

• Geographical aggregation: aggregate all the prefixes that originated from the same origin AS and the same geolocation

– Do not aggregate prefixes with different AS paths!

– Preserve BGP AS path diversity

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Evaluation: GIRO Aggregation

• GIRO achieves a 75% table size reduction compared to BGP

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Incremental deployment?

• We do not have this:

ASN geolocation SID Subnet and host

• Would need IPv6 bits to fit it all in address field …

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– Configure each BGP router with geographic location informaiton

– Define a new BGP "location" attribute to be associated with each AS hop (by usingcommunities)

– Enables each router to calculate the total path length xinC, yinC

C

B

A

xoutB, youtB

xinB, yinB

xoutA, youtA

xorigin, yorigin

But we can do this!

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Conclusion and future work

• Geolocation information can help improve path selection under routing policy constraints

• Embedding ASN and geographical information in IP address can help improve routing scalability through aggregation

• Exploring the possibility of utilizing geolocation in BGP routing, moving forward w/ an I-D very soon…

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Questions?

rveloso@cs.ucla.edu

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Does shortest-path policy cost more locally?

• Comparison between early-exit, late-exit, and shortest-path policy

• Shortest-path policy can reduce global cost significantly withoutsacrificing much of local cost

Global cost(geographical distance)

Local cost

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Internet and Autonomous Systems

AT&TSprint

Verizon

•Autonomous System: a set of routers or networks under the same administration

•Border routers exchange routing updates via the Border Gateway Protocol (BGP)

•Reachability announced through the form of prefixes, i.e. chunks of IP addresses

24.143.92/24

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Evaluation: GIRO Aggregation

• GIRO achieves a 75% tablesize reduction compared to BGP

• About 40% of GIRO entries resulted from topological aggregation• 60% of entries resulted from geographical aggregation

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Inremental deployment?

• Incremental deployability of GIRO:– Can embedd geographic info into BGP communities

• What information to include in routes: absolute location or relative distance?– ISPs want to disclose minimal info about their

networks– Geolocation info can help in doing fault diagnosis

• GIRO can also help in:– Prefix hijacking: prefix ownership problem is solved;

false link attacks can be mitigated– Source address spoofing, if border routers at origin

net stamp (some) data pkts with their geolocation