modeling the border gateway protocol xenofontas dimitropoulos george riley georgia institute of...

Modeling the Border Gateway Protocol

Xenofontas Dimitropoulos

George Riley

Georgia Institute of Technology

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Outline

BGP background and motivation. Modeling BGP.

– BGP++ development approach.– BGP++ features.

Work in progress and future plans.

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is the default interdomain routing protocol of the Internet.

“is the glue that holds the Internet together”. is a protocol of critical importance.

What is BGP ?

BGP routers

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BGP increased interest

BGP does not work well.– Delayed convergence– Divergence issues– Incompatible vendor

implementations– Misbehavior of flap

dampening– Correlation between worm

propagation and Internet instability.

– 20-25% of paths are inflated.

Taken from Craig Labovitz, G. Robert Malan, Farham Jahanian

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BGP problem prone characteristics

Distributed nature

of BGP

Flexibility leftto the operator

in the form of policies

Irregular abrupt

growth of the Internet

“BGP is not a well understood protocol”

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Outline

BGP background and motivation. Modeling BGP,



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What is BGP++ ?

C++ implementation of BGPv4, developed for ns-2.

Agent

Add. Classifier

ns node

Port Classifier

bgpd

Zebradeamonbgpd ospfd ripd

Unix routing table

GNU Zebra software architecture

Figure 1. Zebra bgpd and ns-2 integration.

BGP++ is GNU Zebra bgpd patched to work with ns-2.

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Development Approach Outline

To incorporate GNU Zebra bgpd in ns-2:– Convert C code to C++.– Interleave Zebra scheduler with simulator

scheduler. – Use FullTcp API instead of BSD sockets.– Modify configuration and logging facilities

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Convert C code to C++.

C functions are converted into C++ functions, members of the BGP class.

C global variables are converted into member variables of the BGP class.

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main() {

}

Zebra bgpd vs ns-2 scheduling

main() {

}

initializations

select()

execute

initializations

fetch

execute

Scheduler queueMultiplex IO streams

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Interleaved scheduling

main() {

}

initializations

select()

execute

bgp_main()

post_select()

pre_select()

ns2 scheduler queue

bgpd start event

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Replace BSD sockets with TcpFull

Dynamically tear up/down of tcp connections. Slightly modify tcp-full to notify the

application when the connection moves:– From SYN_RCVD to ESTABLISHED– From SYN_SENT to ESTABLISHED– From ESTABLISHED to CLOSE_WAIT

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Further modifications

Modify Zebra facilities to support OO environment, e.g. logging and configuration.

Get rid of all unnecessary features, e.g. telnet interface.

Dig in the code.

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Outline

BGP background and motivation. Modeling BGP,



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ns-2

set r [new BgpRegistry]set fin 400 ; # finish time

set BGP1 [new Application/Route/Bgp]

$BGP1 register $r$BGP1 finish-time $fin$BGP1 config-file

/sth/bgpd1.conf$BGP1 attach-node $n1

.tcl configuration configuration configuration configuration configuration configuration

BGP routers

BGP++ configuration

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BGP++ configuration

Use router configuration commands that are used by Zebra to configure simulated routers.

Approximately 320 supported commands. Only few new ns-2 commands added.

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Configuring BGP instances

[xdimi@enzo example1]$ more bgpd1.conf!Local AS and local IP addressrouter bgp 1bgp router-id 192.38.14.1

!Neighborsneighbor 192.38.14.2 remote-as 2

!Networks advertisednetwork 190.0.0.0 mask 255.0.0.0network 189.0.0.0 mask 255.0.0.0log file bgpd1.log

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Run time configuration instead of telnet interface.

$ns at 10 “$BGP1 execute \”no neighbor 192.38.14.2\””

$ns at 15 “$BGP3 execute \”show ip bgp\””

$ns at 20 “$BGP2 execute \”neighbor 192.38.14.3 \ advertisement-

interval 20\””

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BGP++, configuring policies

Route Maps “route-map” Access Lists “ip access-list” Community Lists “ip community-list” AS path access lists “ip as-path access-list” Prefix Lists “ip prefix list”

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Validation

Run several simple validation tests. Recreate same topology in lab and compare. Minimum modifications on “core” of Zebra

software.

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Future Work

Use BGP++ with pdns to see how large we can get.

Examine BGP convergence time at scales. Integrate BGP++ with GTNetS.

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Recap

Big scale simulations are necessary in BGP research.

BGP++: a BGP implementation for ns-2– Development approach.– Features

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?Questions

modeling the border gateway protocol xenofontas dimitropoulos george riley georgia institute of...

Documents

c functions

c functions

modeling bgp

bgp class

bgp development

c global variables

zebra scheduler

c implementation of