Sensibility analysis of BGP convergence and scalability using network simulation

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Sensibility analysis of Sensibility analysis of BGP convergence and BGP convergence and scalability using scalability using network simulationnetwork simulation

Sensibility analysis of Sensibility analysis of BGP convergence and BGP convergence and scalability using scalability using network simulationnetwork simulation

Wolfgang Mühlbauer

5. Oktober 2004


OutlineOutlineOutlineOutline

• Running the experiments

• Influence of MRAI timer settings on – convergence times– number of updates

• Propagation of updates– number of affected ASes– propagation radius


Experiments - SSFNetExperiments - SSFNetExperiments - SSFNetExperiments - SSFNet• Network simulation with SSFNet

– global view– existing BGP implementation

• Modifications to SSFNet– Modeling the behavior of Cisco routers

• Normal distribution of MRAI timer value• Community values• Best Path Selection Process, …

– Configuring link failures– MRAI timer basis: per-peer or per-prefix, …


Experiments – Doing Experiments – Doing simulationsimulation

Experiments – Doing Experiments – Doing simulationsimulation

• AS Pairs: define topology, reflect commercial relationships (e.g. 12>13)

• Subtree extraction: reduce complexity and size of sample networks

• DML Files: configuration files, input for SSFNet

Subtree (AS Pairs)

AS Pairs DML FilesSimulation

SSFNet


Experiments – DML FilesExperiments – DML FilesExperiments – DML FilesExperiments – DML Files

• Topology Converter: Automatical generation of DML files out of AS Pairs

• Configurable BGP parameters:– MRAI timer– Link failure dynamics– Interior structure of ASes (route reflectors, …)– WRATE, SSLD– …


Experiments – Sample Experiments – Sample topologiestopologies

Experiments – Sample Experiments – Sample topologiestopologies

# ASes # external links

based on AS Pairs?

Middle Topology 15 27 no

Topology 1140 95 1145 yes (2003)

Topology 7774 105 614 yes (04/2004)

Middle Topology





• Propagation of updates– number of affected Ases– propagation radius


MRAI – How it worksMRAI – How it worksMRAI – How it worksMRAI – How it works

AS 3

AS 1AS 2

AS 4

AS 5



AS 3

AS 1AS 2

AS 4

AS 5

AS 1 issues an update to AS 2 and AS 3



AS 3

AS 1AS 2

AS 4

AS 5

AS 2 "passes on" the information to AS 4



AS 3

AS 1AS 2

AS 4

AS 5

AS 4 "passes on" the information to AS 5

timer instance is started



AS 3

AS 1AS 2

AS 4

AS 5

AS 3 sends its update to AS 4 not until now!



AS 3

AS 1AS 2

AS 4

AS 5

AS 4 may prefer to reach AS 1 via AS 3, but …

timer is not expired yet

?



AS 3

AS 1AS 2

AS 4

AS 5

update is sent, now AS 4 can reach AS 1 via AS 3

timer expires


MRAI – SimulationsMRAI – SimulationsMRAI – SimulationsMRAI – Simulations

• Automatical testing of 3 dimensions:

• For Topology 7774 measure:– Convergence time– Number of external updates

different link failures (5)

MRAI timer values in sec (4,5,10,...,60)

different seeds (20)

simulation


MRAI – ResultsMRAI – ResultsMRAI – ResultsMRAI – Results


MRAI – per prefix or per MRAI – per prefix or per peerpeer


per peer per prefix

0.0.0.1/26

0.0.0.2/26




• used topologies: – Topology 1140– Topology 7774

• testing of 4 dimensions– 5 different failure scenarios– different MRAI timer values (4s, 5s, 10s, …, 60s)– per-peer and per-prefix timer basis– 3 different seeds for random number generator

• we measure – convergence times– number of external updates


MRAI – per-prefix vs per-MRAI – per-prefix vs per-peerpeer

MRAI – per-prefix vs per-MRAI – per-prefix vs per-peerpeer





• Propagation of updates– number of affected Ases– propagation radius


Propagation – Update Propagation – Update RadiusRadius


radius 0

radius 0




radius 1

radius 1

radius 1

radius 1radius 1




radius 2

radius 2


Propagation – Affected Propagation – Affected ASesASes


1) US to D

2) D to US

US providers use link 1 for German destinations

German providers use link 2 for US destinations




1) US to D

2) D to US

Link 1 fails due to some reason




US to D2) D to US

Even traffic from US to D is now routed over link 2 But: Routers in D won‘t get an update message and are therefore not „affected“


Propagation – Link Propagation – Link ClassificationClassification

Propagation – Link Propagation – Link ClassificationClassification

• classify ASes according to their commercial relationships: – tier1 ASes: no provider– stub ASes: no customer– middle Ases: all the rest

• classify external links according to the ASes they connect: tier1-tier1, tier1-middle, middle-middle,

middle-stub, stub-stub

• Harmfulness of links reflected?


Propagation - Propagation - SimulationsSimulations

Propagation - Propagation - SimulationsSimulations

• used topologies:– Topology Middle – Topology 1140– Topology 7774

• testing of 3 dimensions– 10 different failure scenarios– different link categories– 3 different seeds for random number generator

• we measure – number and ratio of affected ASes – mean and maximum of propagation radius






Propagation – Affected Propagation – Affected ASesASesTopology 7774


Propagation - RadiusPropagation - RadiusPropagation - RadiusPropagation - Radius


Danke fürs Zuhören!Danke fürs Zuhören!Danke fürs Zuhören!Danke fürs Zuhören!

Email: [email protected]

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Sensibility analysis of BGP convergence and scalability using network simulation