SIGCOMM'93 Open shortest path first (OSPF) routing protocol simulation

Open Shortest Routing Deepinder

Sidhu,

Maryland

Path

First

Protocol

Tayang

Center

Fu,

for

(OSPF)

Simulation*

Shukri

Abdallah

and

Telecommunications

Department

of Computer

University

MD

Nairt &

Science

of Maryland

Baltimore,

Raj

Research

—

BC

21228

and Institute

for

Advanced

University

Computer

of Maryland

College

Park,

Rob

Studies

—

MD

CP

20742

Coltun

Consultant

Abstract

At

each

router,

tinuously Open

Shortest

hierarchical routing

First

routing

Election

stant

time,

input

buffers,

Router(DR)

three

has a limited for buffers

Election

and

the

Flooding

Protocols

election

time

and

causes

an oscillatory

*This Defense

research at the

vie ws and

policies,

Defense

either

not

in

this

or implied,

the

in conof

4000

increases

the

put

document

behavior.

County.

as representing of the

of

Corporation,

13595

and

the of-

Department

Dnlles

buffers

the

of

Technol-

network,

by

for link

BI)R

ber

of unacknowledged

within

RxmtInterval.

works,

the input

a small

Reducing

changes

the

the value

bootup-convergence-time

at of

20, 50 and

speed exceeds the

ret ransmissions. from

and

three

of 4000 is due

retranstimes

packets

For

Kbps

neton the

80 router buffer

at high

link

net-

size clras-

(3)

bootup-convergence-time. of the RxmtInterval

in

nunl-

received

impact

the

in the input

the

increase

to large

size has little

inThe

to 6000

The

flooding

80

results:

(2) For 20 and 50 router

buffer

change

fail

shows three

respectively.

bootup-convergence-time

the

is bounded

as link

two

speeds

50 Mbps

conIn

of overflowing

causing

the

tically

53

the

using

probability

is bounded

DR (3)

in bootup-convergence-time

above

work,

the

A simulation

networks,

bootup-convergence-time.

VA 22071

Permission to copy without fee all or part of this material is granted provided that the copiee ara not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. SIGCOMM’93 - Ithaca, N. Y., USA 19193 ~ 1993 ACM 0-89791-61 9-01931000910053 . ..S 1.50

and

Protocol,

increases

RxmtInterval

of

Govermnent. Netrix

Kbps,

DR

HelloInterval.

Flooding

mission

The

are those

the

point-to-point

increase

Department

the

of

instability.

the DR-agreement-time

(1) For the 50 router

the

by the

OSPF

Router-ID

causing

when

by twice

router

between

Baltimore

be interpreted

expressed

address:

Herndon,

in part

of Maryland contained

and should

or the U.S.

t present ogy Dr.,

University

conclusions

the authors ficial

was supported

above

(1)

number

case,

the same time,

of the

results:

can be elected

a competition

worst

to support

A simulation

shows

(2) If a router

is a dynamic,

designed

networks. Protocol

Designated

(OSPF)

protocol

in TCP/IP

OSPF The

Path

the

changes

lowers speeds.

the

1

Introduction

in the list router

Open

Shortest

hierarchical routing ing

Path

First

routing

in TCP/IP

protocol

rithms:

Election,

Flooding

ing

information

The

The

Hello,

distribute within

shortest-path In

this

it elects

rout-

in the

algo-

value

and Shortest-

synchronize

the Election

and Flooding

tion

2 presents

and

the

itself

in

Protocols

Flooding

Protocols.

study

of the

Section

of Sec-

event

3 contains

Election

(DR)

and

of the discrete

and Flooding

Protocol

distribute

and

among the

sages

within

the

is

BDR

fields each

containing

among

that

of the

hello

router

router

absence

a hello

packet

terDeadInterval. a bidirectional

order At

a list

a hello X

from

router

of router

Y.

neighbor

X

when

are eligible

routers The

are set We

also

in zero sec-

routers

was booted

is booted

and

We assume

runs

tv – t$ is the

in the

at time

at time

t.

tg such

inter-boot-time,

at time

are booted

At

seconds,

in increasing

experiment

is repeated

for

la

shows

the

result

for

At

lb

shows

the

result

for

At = 30 and

la,

the

increase

= 7 seconds,

the DR-election-time

number

of the

lb,

la,

at routers

network.

to

the

in Fig.

executed

explanation

Fig.

To explain

to a broadcast

this

In

DR-election-time of events

40

increases

of routers.

is constant.

the sequence

we generalize

Then,

a network

of n

routers. At time

7 seconds,

it broadcasts

time

detects

Id

does not

receive

seconds.

of RouY

router

delays.

Protocol

tz, then router

100 routers

RouterDeadIn-

of each

Rv was booted

R1 and Rz attached

X dis-

router

elects

of input

Timer,

R.

DR-election-time

X

a period

10 to

processing

all routers

In Fig.

we trace

Hel-

from

for the first

is booted is to deter-

amount

router

with

linear

DR

packet

Router

considers X

the

its Router-Id,

Router

Y for X

Every a hello

packet,

receives

router

Fig.

linearly

A

the

router

respectively.

If router

of Router-Id.

Figure

Elec-

of Router-Ids

Y when

Router

the

using

packet.

wins

of 7, 10, 22, 30 and 40 seconds.

and

routers

is positive.

a BDR

information

Y when

from

in

transmits

and

covers the

X

other

X has received

Within

seconds.

participate and

tu z

of mes-

information other

and

state.

from

Timer

the Election

and the remaining

system. to

Router-Priority

whom

packet

number

from

of

t2 – tl,on a broadcast

10 seconds

At. The first

to

information

topology

a DR

Router-Priority

a hello

the

that

experiment

Wait

Hello

Initially,

that

Router (BDR)

network.

information

if its

nominates

loInterval, its

broadcast

eligible

Protocol

and

reduces

autonomous

router

router

DR

to

topology

a broadcast

topology

the

A tion

on

needed

and hides

Router

synchronize

routers

network,

a Designated

of this

The

the

and the next

elects

A null

absence

the winning-DR

unlimited

propagation

DOWN

Designated

the first

at which

sizes vary

buffers.

zero

Pro-

Protocol

a Backup

the

to the router

at which

have

and

onds.

The

Router-Id

Time

network

assume

Election

its

packet.

“winning-DR’).

DR-election-time,

to 40, 40 and

t Ocols.

2.1

inserts hello

if

net work,

terval

of the Election

sent by

a DR(BDR)

indicates

We refer

objective

the

output

the results

fields

as the

The

mine

The

we present

simulation

two

Election

itself.

Election

Simulation

this section,

In

and

and t2 be the time

conclusions.

OSPF

packet

itself

of the

and the BDR.

all of which

2

declare

field

these

Initial

the

of OSPF.

results

to

DR(BDR)

DR(BDR)

the election

system.

computes

a simulation

simulation

and

is said

Let tl be the time

we present

in the hello

rout-

autonomous

algorithm

DR

and Flood-

tree. paper,

summary

OSPF

Election,

an

A router

support

interrelated

and

Shortest-Path-First

to

The

of

(SPF).

Protocols

[1].

a collection

the Hello,

ing

is a dynamic,

designed

networks

is

Path-First

‘( OSPF)

protocol

of Router-Ids

Y.

and

time

as

enters

sees its Router-Id

the

14 seconds, the

WAIT packet

from

for

router

broadcasts

state.

RI

is booted

containing state

when it

router

packet

WAIT

Similarly,

the hello

54

a hello

enters

when

Router

R2 at time

its

up,

Router-

a period

of 40

R2 is booted a hello RI

upon

packet

at and

receiving

14 seconds

estab-

lishes one-way seconds,

communication

the second

casts a hello R2. lishes

with

receiving

packet,

both

communication

with

munication

becoming

router

the

pires

when

WAIT

state

or a Backup-Seen

A Backup Rx if R.

receives

Rv such that

packet

itself

in the WAIT as DR

state,

from

4 g 3rm-

A

Timer

ex-

’2001

router

and declares !

.a .g

themselves

time

pires,

and

47 seconds, RI

elects

the

Wait

R2 as the

Timer

DR

a higher

Router-Id.

R1 broadcasts

elect ion

in its

packet.

hello

at RI

ex-

because

R2 has

the result

of the

A Backup

~, ,

Is

or BDR.

At

S-

“~-

to be the BDR,

declare

607080901CCI Newark

Since R1 and .R2 are

cannot

1020304Q50

router

another

itself

a BDR.

they

‘w 4al -

com-

at any

to be the DR

it has not elected

.!

a hello

election.

Wait

is triggered

a hello

[.0

RI.

is triggered.

(1) Rv declares

or (2) RV declares that

if its

event

_Seen event

router

for

1

700-

and

bidirectional

candidates

ma

R2 estab-

R2 broadcasts

establish

17

RI broadof RI

packet,

routers

exits

router

hello

24 seconds,

At time

the Router-Ids

this

bidirectional

.At time

R2.

HelloInterval,

packet

Upon

with

~ Iriler-nca

SO

60

NeNwuk

at

R2 is not

ing

itself

when

the

Wait

self as the time,

triggered

to be DR Timer

DR

and

the Hello

gered

R2 as the seconds, network

is not

time

BDR.

At

at R2 expires

to run

and

the

itself

declares

itself

by broadcasting

DR-election-time

for

as a BDR a hello

At

Finally, onds,

is trig-

cation

time

to the

generalize

network RI, R2,.

57

R.

Thus,

of two

routers

the is

n

routers

... Rn.

The

boot

40 seconds WAIT cause (1