Performance Evaluation of BGP-4+ in IPv4/IPv6

T.BlagaT.Blaga –– Performance Evaluation of BGP Performance Evaluation of BGP –– RoEduNetRoEduNet 2005 2005 –– SovataSovata, May 20, May 20--22, 200522, 2005

Performance Evaluation of BGPPerformance Evaluation of BGP--4+ 4+ in IPv4/IPv6in IPv4/IPv6

A. Katona, V. Dobrota T. Blaga, G. LazarTechnical University of Cluj-Napoca, Department of Communications E-mail: [email protected], {Virgil.Dobrota, Tudor.Blaga, Gabriel.Lazar}@com.utcluj.ro



AgendaAgenda

IntroductionIntroductionBGPBGP--4+ Basics4+ BasicsSimulation of BGPSimulation of BGP--4+4+Experiment with a TwoExperiment with a Two--Router ScenarioRouter ScenarioExperiments with ThreeExperiments with Three--Router ScenariosRouter ScenariosConclusionsConclusions


IntroductionIntroduction

BBorder order GGateway ateway PProtocol version rotocol version 4+4+the dethe de--facto standard interdomain routing protocolfacto standard interdomain routing protocol

IETF, 1995 IETF, 1995 –– RFC 1771RFC 1771

Exchange routing information between different Exchange routing information between different Autonomous Systems (ASs)Autonomous Systems (ASs)

A protocol of crucial importance to the InternetA protocol of crucial importance to the Internet

Support for:Support for:CIDR (Classless InterCIDR (Classless Inter--Domain Routing)Domain Routing)Routing policiesRouting policies

One of the most complex routing protocolsOne of the most complex routing protocols


Autonomous SystemsAutonomous Systems

Set of routers and networks under a single Set of routers and networks under a single technical administrationtechnical administration

a corporate, organization, or ISP networka corporate, organization, or ISP network

Having a single, wellHaving a single, well--defined routing policydefined routing policy

Run an Interior Routing Protocol (IGP) insideRun an Interior Routing Protocol (IGP) inside

Identified by AS Number Identified by AS Number (ASN)(ASN)


AgendaAgenda



BGP OverviewBGP Overview

Two neighbouring BGP routers form a peer Two neighbouring BGP routers form a peer connection to exchange routing informationconnection to exchange routing information

Use TCP as transport protocol (port 179)Use TCP as transport protocol (port 179)reliable communicationreliable communication

Initial exchange of all the routesInitial exchange of all the routesonly only incremental updatesincremental updates are sent afterwardsare sent afterwards

External BGP and Internal BGPExternal BGP and Internal BGPpeers can be in different ASs or in the same ASpeers can be in different ASs or in the same AS


BGP MessagesBGP Messages1.1. OPENOPEN –– establishes a BGP peer connectionestablishes a BGP peer connection

first message sent after TCP connection is first message sent after TCP connection is establishedestablished

2.2. UPDATEUPDATE –– sends routing informationsends routing informationadvertises advertises or or withdrawswithdraws routesroutes

3.3. NOTIFICATIONNOTIFICATION –– informs about an errorinforms about an errorshut down the connectionshut down the connection

4.4. KEEPALIVEKEEPALIVE –– verifies the connection stateverifies the connection statesent periodicallysent periodically


BGP Finite State MachineBGP Finite State Machine

OpenConfirm

Idle

Connect

OpenSent Active

Established

The process of establishing and The process of establishing and maintaining a BGP peer connectionmaintaining a BGP peer connectionEvents (13 of them)Events (13 of them)Timers: Timers: HoldHold, , KeepAliveKeepAlive, , ConnectRetryConnectRetry, , StartStart



OpenConfirm

Idle

Connect

OpenSent Active

EstablishedIdleIdle state:state:

no connection and no no connection and no resources allocatedresources allocated



OpenConfirm

Idle

Connect

OpenSent Active

Established ConnectConnect state:state:initiate TCP connectioninitiate TCP connection



OpenConfirm

Idle

Connect

OpenSent Active

Established

ActiveActive state:state:if TCP was not if TCP was not

established, wait for peer, established, wait for peer, or try again lateror try again later



OpenConfirm

Idle

Connect

OpenSent Active

Established

OpenSentOpenSent state:state:TCP established TCP established –– send send

OPEN and wait for OPEN and wait for OPEN from peerOPEN from peer



OpenConfirm

Idle

Connect

OpenSent Active

Established

OpenConfirmOpenConfirm state:state:wait for KEEPALIVE, wait for KEEPALIVE,

confirming OPENconfirming OPEN



OpenConfirm

Idle

Connect

OpenSent Active

Established

EstablishedEstablished state:state:routing information routing information

(UPDATE messages) (UPDATE messages) can be exchangedcan be exchanged


BGP Path AttributesBGP Path Attributes

information attached to routesinformation attached to routesused in the decision processused in the decision process

ORIGINORIGIN –– from where was the route obtainedfrom where was the route obtainedAS_PATHAS_PATH –– list of traversed ASslist of traversed ASsNEXT_HOPNEXT_HOP –– IP address of next hop routerIP address of next hop routerAGGREGATORAGGREGATOR & & ATOMIC_AGGREGATEATOMIC_AGGREGATE ––attached to aggregate routesattached to aggregate routesLOCAL_PREFLOCAL_PREF & & MULTI_EXIT_DISCMULTI_EXIT_DISC –– attach degree attach degree of preference to external links and routesof preference to external links and routesWEIGHTWEIGHT –– force the decision process to pick a routeforce the decision process to pick a routeothersothers


AgendaAgenda



Simulation of BGPSimulation of BGP--44

NSNS--22 –– Network Simulator version 2Network Simulator version 2

a very popular network simulatora very popular network simulatorbased on based on OTclOTcl (Object Tool Command (Object Tool Command Language)Language) programming languageprogramming language

BGP++BGP++

NSNS--2 extension implementing BGP2 extension implementing BGP--4+4+based on based on bgpdbgpd (BGP Daemon)(BGP Daemon) from Zebra from Zebra routing softwarerouting softwarecommand syntax similar to Cisco routerscommand syntax similar to Cisco routers


BGP simulation with nsBGP simulation with ns--2 and BGP++2 and BGP++

1.1. create simulation create simulation script (OTcl)script (OTcl)

nodesnodeslinkslinksBGP objectsBGP objectseventsevents

nsns--22BGP++BGP++

for {set i 0} {$i <= 2} {incr i} {puts "Creating router $i“puts " - config file: $opt(confdir)/bgpd$i.conf“puts " - log file: $opt(outdir)/bgpd$i.log“set router($i) [$ns node] $router($i) label "Router $i“set bgp($i) [new Application/Route/Bgp]$bgp($i) register $r$bgp($i) finish-time $opt(stop) $bgp($i) config-file

.tcl.tcl





2.2. create router create router configuration configuration filesfiles for {set i 0} {$i <= 2} {incr i} {

puts "Creating router $i“puts " - config file:$opt(confdir)/bgpd$i.conf“puts " - log file:$opt(outdir)/bgpd$i.log“set router($i) [$ns node] $router($i) label "Router $i“set bgp($i) [new Application/Route/Bgp]$bgp($i) register $r$bgp($i) finish-time $opt(stop) $bgp($i) config-file

.tcl.tcl

router bgp 65502bgp router-id 192.168.10.12

neighbor 192.168.10.10 remote-as 65500

network 172.22.0.0 mask 255.255.0.0

debug bgp



network 172.21.0.0 mask 255.255.0.0

debug bgp


neighbor 192.168.10.11 remote-as 65501neighbor 192.168.10.12 remote-as 65502

network 172.20.0.0 mask 255.255.0.0

debug bgp

.conf.conf

nsns--22BGP++BGP++





2.2. create router create router configuration configuration filesfiles

3.3. run simulationrun simulationlog fileslog files

for {set i 0} {$i <= 2} {incr i} {puts "Creating router $i“puts " - config file:$opt(confdir)/bgpd$i.conf“puts " - log file:$opt(outdir)/bgpd$i.log“set router($i) [$ns node] $router($i) label "Router $i“set bgp($i) [new Application/Route/Bgp]$bgp($i) register $r$bgp($i) finish-time $opt(stop) $bgp($i) config-file

.tcl.tcl



network 172.22.0.0 mask 255.255.0.0

debug bgp



network 172.21.0.0 mask 255.255.0.0

debug bgp


neighbor 192.168.10.11 remote-as 65501neighbor 192.168.10.12 remote-as 65502

network 172.20.0.0 mask 255.255.0.0

debug bgp

.conf.conf

2004/05/17 01:32:23 5.453414 BGP: 192.168.10.12 [FSM] BGP_Start (Idle->Connect)2004/05/17 01:32:23 5.453414 BGP: 192.168.10.12 went from Idle to Connect2004/05/17 01:32:23 5.453414 BGP: 192.168.10.12



.log.log

nsns--22BGP++BGP++


AgendaAgenda



Experiment with a TwoExperiment with a Two--Router ScenarioRouter Scenario

Connection setup and exchange of routing Connection setup and exchange of routing informationinformationStudy the effects of different values for the Hold Study the effects of different values for the Hold Timer and KeepAlive intervalTimer and KeepAlive intervalConnection establishment time and time elapsed Connection establishment time and time elapsed in different states of the FSMin different states of the FSM

AS 65500AS 65500 AS 65501AS 65501

192.168.10.10192.168.10.10 192.168.10.11192.168.10.11

R0R0 R1R1

172.20.0.0/16172.20.0.0/16 172.21.0.0/16172.21.0.0/16


Visualization of Log Messages in namVisualization of Log Messages in nam


Connection Setup Time MeasurementConnection Setup Time MeasurementConnection setup time Connection setup time vs. link delayvs. link delay(1.5 Mbps link)(1.5 Mbps link)

Connection setup time Connection setup time vs. link bandwidthvs. link bandwidth(10 ms delay)(10 ms delay)

establish time [sec]

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

0.064 0.128 0.256 0.512 1 1.544 2.048 5 10 50 100

link bandwidth [Mbps]

establish time [sec]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 50 100 150 200

link delay [ms]


Amount of Traffic Generated by BGPAmount of Traffic Generated by BGP

most of the data sent is the overhead of TCP most of the data sent is the overhead of TCP and IPand IP

0

500

1000

1500

2000

2500

3000

R0 R1 Total

Bytes sent (TCP)

Bytes sent (BGP)

0

500

1000

1500

2000

2500

3000

R0 R1 Total

Bytes sent (TCP)

Bytes sent (BGP)

5 minutes of operation5 minutes of operation

connection setup, exchange of connection setup, exchange of routes and periodic KEEPALIVE routes and periodic KEEPALIVE messagesmessages

the same, plus one route the same, plus one route oscillating every 30 secondsoscillating every 30 seconds


AgendaAgenda



ThreeThree--Router Scenario (1)Router Scenario (1)

R0 provides transit service between R1 and R2R0 provides transit service between R1 and R2Limitation of transit service by enforcing a routing Limitation of transit service by enforcing a routing policy at R0policy at R0

AS 65501AS 65501 AS 65502AS 65502

192.168.10.11192.168.10.11 192.168.10.12192.168.10.12

R1R1 R2R2172.21.0.0/16172.21.0.0/16 172.22.0.0/16172.22.0.0/16

R0R0AS 65500AS 65500

192.168.10.10192.168.10.10

172.20.0.0/16172.20.0.0/16



R0 performs aggregation of the routes received R0 performs aggregation of the routes received from R1 and R2from R1 and R2Reduction in the size of the routing tablesReduction in the size of the routing tables

AS 65501AS 65501 AS 65502AS 65502

192.168.10.11192.168.10.11 192.168.10.12192.168.10.12

R1R1 R2R2172.20.0.0/16172.20.0.0/16 172.22.0.0/16172.22.0.0/16

R0R0

AS 65500AS 65500192.168.10.10192.168.10.10

172.19.0.0/16172.19.0.0/16

172.21.0.0/16172.21.0.0/16 172.23.0.0/16172.23.0.0/16

Route aggregation:Route aggregation:

•• 172.20.0.0/16172.20.0.0/16•• 172.21.0.0/16172.21.0.0/16•• 172.22.0.0/16172.22.0.0/16•• 172.23.0.0/16172.23.0.0/16

172.20.0.0/14172.20.0.0/14



The shortest path is chosen as the bestThe shortest path is chosen as the bestThe path selection can be influenced with the The path selection can be influenced with the WEIGHT attributeWEIGHT attributeDetection and elimination of routing loopsDetection and elimination of routing loops

AS 65501AS 65501 AS 65502AS 65502

192.168.10.11192.168.10.11 192.168.10.12192.168.10.12

R1R1 R2R2172.21.0.0/16172.21.0.0/16 172.22.0.0/16172.22.0.0/16

R0R0

AS 65500AS 65500192.168.10.10192.168.10.10

172.20.0.0/16172.20.0.0/16


AgendaAgenda

IntroductionIntroductionBGPBGP--4+ Basics4+ BasicsSimulation of BGPSimulation of BGP--4+4+Experiment with a TwoExperiment with a Two--router Scenariorouter ScenarioExperiments with ThreeExperiments with Three--router Scenariosrouter ScenariosConclusionsConclusions


ConclusionsConclusions

The Hold Timer is used to detect failuresThe Hold Timer is used to detect failuresConnection setup time: at least 3 x RTTConnection setup time: at least 3 x RTTBGP data traffic is not very significant:BGP data traffic is not very significant:

KEEPALIVE messages every 60 seconds: 21 bpsKEEPALIVE messages every 60 seconds: 21 bpsOne route oscillating every 30 sec: at least 34 bpsOne route oscillating every 30 sec: at least 34 bps

A BGP router provides transit service by defaultA BGP router provides transit service by defaultImplementation of routing policies is neededImplementation of routing policies is needed

The most important attribute is AS_PATH:The most important attribute is AS_PATH:Shortest AS_PATH is the best route (by default)Shortest AS_PATH is the best route (by default)Detection of routing loopsDetection of routing loops


Future WorkFuture Work

Experiments with path selection with different Experiments with path selection with different path attributespath attributesSimulation of more complex topologies, in order Simulation of more complex topologies, in order to study route stability and convergence to study route stability and convergence behaviourbehaviourPractical experimentation using Cisco routers Practical experimentation using Cisco routers and Zebra routing software in IPv6and Zebra routing software in IPv6


ReferencesReferences

REKHTER, Y. & T. LI REKHTER, Y. & T. LI –– ““A Border Gateway A Border Gateway Protocol 4 (BGPProtocol 4 (BGP--4)4)””, , RFC 1771RFC 1771, 1995, 1995HALABI, S. & D. McPHERSON HALABI, S. & D. McPHERSON –– ““Internet Internet Routing Architectures, 2Routing Architectures, 2ndnd Ed.Ed.””, Cisco, 2000, Cisco, 2000DOYLE, J. & J. DEHAVEN DOYLE, J. & J. DEHAVEN –– ““Routing TCP/IP Routing TCP/IP Vol. IIVol. II””, Cisco, 2001, Cisco, 2001NSNS--2:2: http://www.isi.edu/nsnam/ns/http://www.isi.edu/nsnam/ns/BGP++: BGP++: http://www.ece.gatech.edu/research/http://www.ece.gatech.edu/research/labs/MANIACS/BGP++/labs/MANIACS/BGP++/

Performance Evaluation of BGP-4+ in IPv4/IPv6

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