/
Putting BGP on the Right Path: A Case for Next-Hop Routing Putting BGP on the Right Path: A Case for Next-Hop Routing

Putting BGP on the Right Path: A Case for Next-Hop Routing - PowerPoint Presentation

alida-meadow
alida-meadow . @alida-meadow
Follow
389 views
Uploaded On 2017-06-07

Putting BGP on the Right Path: A Case for Next-Hop Routing - PPT Presentation

Michael Schapira Joint work with Yaping Zhu and Jennifer Rexford Princeton University Once Upon a Time Internet InterNetwork Routing Small network Single administrative entity ID: 557015

hop routing bgp path routing hop path bgp route rule convergence number engineering maximum rexford ases traffic performance updates

Share:

Link:

Embed:

Download Presentation from below link

Download Presentation The PPT/PDF document "Putting BGP on the Right Path: A Case fo..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.


Presentation Transcript

Slide1

Putting BGP on the Right Path: A Case for Next-Hop Routing

Michael

SchapiraJoint work with Yaping Zhu and Jennifer Rexford (Princeton University)Slide2

Once Upon a Time…

Internet Inter-Network Routing:

Small network

Single administrative entity

NSFNET

Shortest-path routing

distance-vector routingThen....Slide3

Interdomain Routing

Over 35,000

Autonomous Systems (ASes)Interdomain

routing

= routing between

ASes

Border Gateway Protocol (BGP)AT&TQwestComcastSprintSlide4

Today’s Path-Based Routing With BGP

Complex!

configuration errors, software bugs, …Bad convergence!persistent route oscillations, slow convergence, …Vulnerable to attacks!malicious, economically-driven, inadvertent, … and more, and more, and more …bad performance, clumsy traffic engineering, …Slide5

How Can We Fix

Interdomain Routing?

One approach: add mechanisms to an already complex protocolroute flap damping, S-BGP, …Another approach: redesign interdomain routing from scratchHLP, NIRA,

pathlet

routing, consensus routing, …

Our approach

: simplify BGP!Slide6

Background

: Today’s Path-Based Routing With BGP

AS i’s routing policy:ranking

of simple routes from

i

to each destination d

export policyBGP is a path-vector protocol

Receive

route updates

from

neighbors

Choose

single

“best”

route

(ranking)

Send route updates to neighbors

(export policy)Slide7

3

d

1

2

Background

:

Today’s

Path-Based Routing With BGP

32d > 31d

Don’t export 2d to 3

1, 2, I’m available

3, I’m using 1d

a

stable state

is reachedSlide8

AS-PATH = the Route of All Evil

AS-PATH: list of

all ASes on pathoriginally meant for loop-detectionThe AS-PATH is to blame!error-prone, software bugsno/slow convergencelarge attack surfacebad scalability, clumsy traffic engineering, bad performance, …Slide9

Getting Off the AS-PATH

No way back to shortest-path routing…

Our proposal: next-hop routingmake routing decisions based solely on the “next hop”relegate the AS-PATH to its original roleSlide10

Wish List

Loop freedom

Fast ConvergenceSecurityIncentive compatibilityBusiness policiesGood performanceTraffic engineeringScalabilitySimplicitySlide11

Expressiveness vs. Complexity

complexity

expressiveness

not expressive

enough

sufficiently

expressive

extremely

expressive

simple

too complex

shortest-path

routing

next-hop

routing

BGP’s

path-based

routingSlide12

Next-Hop Routing Rules!

Rule 1: use next-hop rankings

4d

3

5

1

2

4 > 3

541d > 53d > 542dSlide13

Next-Hop Routing Rules!

Rule 1

: use next-hop rankings Rule 2: prioritize current routeto minimize path exploration [Godfrey-Caesar-Hagen-Singer-Shenker]2

d

3

1

2=3

Break ties in favor of lower AS number

2=3

Prioritize current routeSlide14

Next-Hop Routing Rules!

Rule 1

: use next-hop rankings Rule 2: prioritize current routeRule 3: consistently exportto avoid disconnecting upstream nodes [Feigenbaum-S-Ramachandran]

3

d

4

1

2

1 > 2,

Export 32d, but not 31d, to 4

1 > 2,

Export 31d

to 4Slide15

Next-Hop Routing Rules!

Rule 1

: use next-hop rankings Rule 2: prioritize current routeRule 3: consistently exportDefn: Node i

consistently exports

w.r.t

. neighbor j

if there is some route R s.t. each route Q is exportable to j iff R ≤i Q.Defn: Node i consistently exports if it consistently exports with respect to each neighboring node j.Slide16

Next-Hop Routing Rules!

Rule 1: use next-hop rankings

Rule 2: prioritize current routeRule 3: consistently export3 deployment schemesConfigure today’s routersCreate new router configuration interfaceBuild new router softwareSlide17

Wish List Revisited

Loop freedom

Fast convergenceSecurityIncentive compatibilityBusiness policiesGood performanceTraffic engineeringScalability

SimplicitySlide18

Wish List Revisited

Loop freedom

Fast convergence?SecurityIncentive compatibility [Feigenbaum-S-Ramachandran]

Business policies

Good performance

Traffic engineering

Scalability?SimplicitySlide19

Existence of Stable State

Existence of stable state not guaranteed

even with next-hop rankings (Rule 1) [Feamster-Johari-Balakrishnan]Thm: If the next-hop routing rules hold, then a stable state exists in the network.What about (fast!) convergence?Slide20

BGP Oscillations

BGP not guaranteed to converge even with next-hop routing! [Griffin-Shepherd-Wilfong]1

d

2

2 > d

1 > dSlide21

The Commercial Internet

ASes

sign long-term contracts.Neighboring pairs of ASes have:a customer-provider relationship

a

peering

relationship

peer

providers

customers

peerSlide22

Gao-Rexford Framework

3 simple conditions that are naturally induced by

the AS-business-hierarchy.Topology condition, Preference condition, Export conditionIf the Gao-Rexford conditions hold, then BGP is

guaranteed

to converge to a stable state.

[

Gao-Rexford]But, this might require exponentially-many forwarding changes! [Syed-Rexford]Slide23

Fast BGP Convergence

Thm

: In the Gao-Rexford framework, next-hop routing convergence to a stable state involves at most O(L2) forwarding changes (L = # links).all network topologiesall timings of AS activations and update message arrivalsall initial routing statesall initial “beliefs”implications for routing changes and number of BGP

updatesSlide24

Simulations

C-BGP simulator. Cyclops AS-level topology, Jan 1

st 2010 (33,976 ASes, ~5000 non-stubs)Protocols: BGP, Prefer Recent Route (PRR), next-hop routingMetrics:

# forwarding changes, # routing changes,

# updates, AS-PATH length

Events: prefix up, link failure, link recoveryMethodology: 500 experiments, 10,000 vantage points (all non-stubs, 5000 stubs)Slide25

Simulation Results

(# Forwarding Changes)

maximum number of BGP forwarding changes > 20maximum number of routing changes in next-hop routing = 3

maximum number of forwarding changes

in PRR = 10Slide26

Simulation Results

(# Routing Changes)

maximum number of BGP routing changes > 160maximum number of routing changes in next-hop routing < 20

maximum number of routing changes

in PRR > 40Slide27

Simulation Results

(# BGP Updates, Non-Stub

ASes)maximum number of BGP updates > 6000

maximum number of updates in next-hop routing < 300

maximum number of updates in PRR > 1000Slide28

Simulation Results

(# Routing Changes, The 0.1% Position)Slide29

Incentive Compatible

Routing Configurations

2d3

1

d > 2

3 > d > 1

2

Each node is getting its best

feasible

next-hopSlide30

Next-Hop Routing is

Incentive Compatible

Thm [Feigenbaum-Ramachandran-S]: In the Gao-Rexford framework, next-hop routing is incentive compatible. (each node is guaranteed its

best

feasible

next-hop)Slide31

Wish List Revisited

Loop freedom

Fast convergenceSecurity?Incentive compatibilityBusiness policiesGood performance?Traffic engineering?ScalabilitySimplicitySlide32

Limitations of Next-Hop Routing

AS-PATH length

AS-avoiding policiesAS-name prependingAS-PATH-based traffic engineeringSlide33

Security, Performance,

Traffic Engineering

Still open research questions.Handled mostly outside the routing protocol.We argue that next-hop routing makes things mostly better.Slide34

Performance

Faster/better convergence than BGP.

much more scalable.But…potential increase in path lengths.bloosely correlated with performance (# routers, physical distance… throughput…).still, significant increase clearly undesirable!Simulation results

: same path length for 97-99% of

ASes

; big increase only for ~0.1%.Slide35

Security

Reduces BGP’s attack surface (AS-PATH length plays no role in routing decisions).

More resilient to economically-driven attacks (incentive compatible).More resilient to misconfigurations (in progress)But… AS-avoiding policies impossible.come with no guarantees. e2e?Slide36

Traffic Engineering

We discuss how traffic engineering can be done without relying on the AS-PATH.

using different next-hop rankings for different (groups of) prefixesusing the BGP communities attribute…Slide37

Multipath Routing

Performance, security and traffic engineering can greatly benefit from multipath routing.

multiple working pathsimmediate response to failuresload balancing among multiple next-hops…Next-hop routing lowers the barrier for making this a reality (work in progress).Slide38

Multipath Routing

Exploiting path diversity torealize the

AS’s own objectivescustomize route selection for neighboring ASesBut... multipath routing is not scalable!

disseminate and store multiple routesSlide39

Multipath Routing is Not Scalable!

d

12

3

4

P

1

P

2

Q

1

Q

2

I’m using P

1

and P

2

I’m using Q

1

and Q

2

I’m using P

1

, P

2

, Q

1

and Q

2Slide40

From AS-PATH to AS-SET

Next-hop routing is more amenable to multipath

nodes don’t care about entire paths… other than for loop detectionDon’t announce routes, announce sets!set = union of ASes on all routesBGP route aggregationSlide41

Neighbor-Specific

Next-Hop Routing

Customizing route selection for neighborsoperational motivation [Kushman-Kandula-Katabi-Maggs]economic motivation [Wang-S-Rexford]

C

1

z

C2C3

d

?

R

1

R

2

R

3

Secure!

Short!

Cheap!Slide42

Neighbor-Specific

Next-Hop Routing

Neighbor-Specific BGP [Wang-S-Rexford]implementable using existing toolsResults for convergence and incentive compatibility extend to multipath!Slide43

Conclusions and

Future Research

BGP is far too complicated!New approach: simplify BGPwithout compromising global and local goals!Directions for future research:getting rid of the AS-PATH?software / configuration complexitymore theoretical and experimental workSlide44

Thank

You