Pathlet Routing P. Brighten Godfrey pbg@illinois.edu Igor - - PowerPoint PPT Presentation

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Pathlet Routing P. Brighten Godfrey pbg@illinois.edu Igor - - PowerPoint PPT Presentation

Nov 28, 2022 231 likes •975 views

Pathlet Routing P. Brighten Godfrey pbg@illinois.edu Igor Ganichev, Scott Shenker, and Ion Stoica {igor,shenker,istoica}@cs.berkeley.edu SIGCOMM 2009 Internet routing challenges Multipath reliability path quality Scalability Policy

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Pathlet Routing

  • P. Brighten Godfrey

pbg@illinois.edu Igor Ganichev, Scott Shenker, and Ion Stoica {igor,shenker,istoica}@cs.berkeley.edu SIGCOMM 2009

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Internet routing challenges

Scalability Multipath reliability path quality Policy

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20 40 60 80 100 120 140 160 180 200

  • 600
  • 400
  • 200

200 400 600 Number of loss burst Starting time (seconds)

Failure injected

Internet routing challenges

[ F. Wang, Z. M. Mao, J. Wang, L. Gao, R. Bush ’06]

Scalability Multipath reliability path quality Policy

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Internet routing challenges

Lowest latency path Path the network picked for you Highest bandwidth path

Scalability Multipath reliability path quality Policy

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Internet routing challenges

Scalability

Internet forwarding table size [Huston ’09]

Multipath reliability path quality Policy

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Internet routing challenges

Scalability Multipath reliability path quality Policy

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Internet routing challenges

Scalability Multipath reliability path quality Policy

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Internet routing challenges

X

Scalability Multipath reliability path quality Policy

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

virtual graph: flexible way to define policy constraints

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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

virtual graph: flexible way to define policy constraints provides many path choices for senders

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Flexibility

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Flexibility

  • can emulate BGP, source

routing, MIRO, LISP, NIRA

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Flexibility

  • can emulate BGP, source

routing, MIRO, LISP, NIRA

  • local transit policies

provide multipath and small forwarding tables

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Flexibility

  • can emulate BGP, source

routing, MIRO, LISP, NIRA

  • local transit policies

provide multipath and small forwarding tables

  • coexistence of different

styles of routing policy

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Flexibility

  • can emulate BGP, source

routing, MIRO, LISP, NIRA

  • local transit policies

provide multipath and small forwarding tables

  • coexistence of different

styles of routing policy

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Flexibility

  • can emulate BGP, source

routing, MIRO, LISP, NIRA

  • local transit policies

provide multipath and small forwarding tables

  • coexistence of different

styles of routing policy

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Design for variation

Design for variation in outcome, so that the outcome can be different in different places, and the tussle takes place within the design, not by distorting or violating it. Clark, Wroclawski, Sollins & Braden, 2002

“Tussle in Cyberspace”

“ ”

––

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Outline

  • The protocol
  • Uses
  • Experimental results
  • Comparing routing protocols
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Pathlet routing

vnode virtual node pathlet fragment of a path: a sequence of vnodes Source routing over pathlets.

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS

Walla Walla New York San Diego Roosterville Crumstown

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS

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vnodes

vnode: virtual node within an AS designated ingress vnode for each neighbor

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vnodes

vnode: virtual node within an AS designated ingress vnode for each neighbor

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vnodes

vnode: virtual node within an AS designated ingress vnode for each neighbor

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vnodes

vnode: virtual node within an AS designated ingress vnode for each neighbor Internally: a forwarding table at one or more routers

router router router

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Pathlets

Forwarding table A B C D Packet route field

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Pathlets

Forwarding table A B C D Packet route field

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Pathlets

7 2

Forwarding table A B C D Packet route field

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Pathlets

7 2

Forwarding table A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2

Forwarding table

7,2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2

Forwarding table

7,2 2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2

Forwarding table

7,2 2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2

delivered! Forwarding table

7,2 2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2 3 ... ... 3 push 7,2; fwd to B

delivered! Forwarding table

7,2 2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C

Packet route field

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Pathlets

7 2 3 ... ... 3 push 7,2; fwd to B

delivered! Forwarding table

7,2 2

A B C D

... ... 2 fwd to D ... ... 7 fwd to C 3

Packet route field

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Dissemination

  • Global gossip fine, except for scalability
  • So, let routers choose not to disseminate

some pathlets

  • Leads to (ironic) use of path vector –– only

for pathlet dissemination, not route selection

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Outline

  • The protocol
  • Uses
  • Experimental results
  • Comparing routing protocols
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Local transit policies

Each ingress egress pair is either allowed or disallowed. Subject to this, any path allowed! Represented with few pathlets: small FIB

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“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

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ingress from a provider ingress from a customer

“All valley-free” is local

“customers can route to anyone; anyone can route to customers”

provider provider customer customer egress to a customer egress to a provider

Forwarding table size: 3 + #neighbors

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Emulating BGP

128.2.0.0/16

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Emulating BGP

128.2.0.0/16

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Emulating BGP

128.2.0.0/16

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Emulating BGP

128.2.0.0/16

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Emulating BGP

128.2.0.0/16

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Mixed policies

local BGP-like local local local

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Outline

  • The protocol
  • Uses
  • Experimental results
  • Comparing routing protocols
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Improved connectivity

BGP-style LT policies Mixed

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Tiny forwarding tables

Forwarding table size CDF

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Tiny forwarding tables

Forwarding table size CDF

BGP pathlet routing, valley-free LT policies current Internet (CAIDA/APNIC): 132,158+ entries:

  • ne per IP prefix

2,264 entries, max 8.48 entries, mean

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Control overhead

2.23x more messages, 1.61x more memory in LT than PV This can likely be improved.

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Outline

  • The protocol
  • Uses
  • Experimental results
  • Comparing routing protocols
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Comparing protocols

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Comparing protocols

Feedback-based routing Strict source routing Pathlet routing NIRA Routing deflections, path splicing LISP BGP MIRO Loose source routing

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Comparing protocols

Feedback-based routing Strict source routing Pathlet routing NIRA Routing deflections, path splicing LISP BGP MIRO Loose source routing

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Conclusion

  • Pathlet routing: source routing over a

virtual topology formed by pathlets and vnodes

  • Highly flexible; supports both “local”

policies with small forwarding tables and many paths, and complex BGP policies

  • Challenges for source routing: Incentives to

provide multiple paths; selecting paths; security; ...

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