momina-RIP

volleyballbeginnerNetworking and Communications

Oct 27, 2013 (3 years and 10 months ago)

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RIP


Routing
Information Protocol

Syeda Momina Tabish

MIT
-

7

Outline


Introduction


History


Version


RIP v1


RIP v2


RIPng


Functioning

RIP


Introduction


One of Interior gateway protocol (IGP) routing
protocols on internal networks.


Helps routers dynamically adapt to changes of
network connections by communicating information
about which networks each router can reach and
how far away those networks are.


Its made obsolete by OSPF and IS
-
IS.


Also sometimes called Rest in Pieces.

RIP


Introduction


A simple intradomain protocol


Straightforward implementation of Distance Vector
Routing


Each router advertises its distance vector every 30
seconds (or whenever its routing table changes) to
all of its neighbors


RIP always uses 1 as link metric


Maximum hop count is 15, with “16” equal to “




Routes are timeout (set to 16) after 3 minutes if they
are not updated

RIP


History


Late 1960s :

Distance Vector protocols were used in the


ARPANET


Mid
-
1970s:

XNS (Xerox Network system) routing

protocol is the precursor of RIP in IP (and

Novell’s IPX RIP and Apple’s routing

protocol)


1982

Release of
routed

for BSD Unix


1988

RIPv1 (RFC 1058)



-

classful routing


1993

RIPv2 (RFC 1388)



-

adds subnet masks with each route entry



-

allows classless routing


1998

Current version of RIPv2 (RFC 2453)

RIP


Message Format


Two Message Types


Request (sent by devices after initialization to
request a unicast copy of a neighbor’s routing
table


Response (sent by RIP speaking devices by
broadcasting every 30 seconds to IP
255.255.255.255)


Send via UDP/520 up to 25 routes per packet
that include IP network, metric, but no subnet
mask

RIP


Normal Operation


For every active RIP interface


Announce known RIP routes out RIP enabled interfaces
every 30s


Process received RIP annoucements by placing routes in
routing table if better than existing route and add 1 to the
hop count


Do not announce things learned on an interface out the
same interface (split horizon)


Only announce if reachable with hop count <
-

15

RIP Timers

Router rip


timers basic update invalid hold down flush


Update 30s (when to broadcast response)


Invalid 180s (when haven’t heard annoucements for
180s, do not use)


Holddown 180s (when neighbor increases metric for
a network, do not accept immediately


Flush 240s (after invalid timer expires, mark as
unreachable metric 16 until time to flush)

RIP v1


RIPv1, defined in RFC 1058


Uses classful routing


Routing updates do not carry subnet
information


Lacking support for variable length subnet
masks


No Support for Router Authentication

RIPv1 Packet Format

One RIP message can
have up to 25 route entries

1: request

2: response

2: for IP

0…0: request full rou
-
ting table

Address of destination

Cost (measured in hops)

1: RIPv1

RIP v2


Developed in 1994


Included the ability to carry subnet information, thus
supporting Classless Inter
-
Domain Routing (CIDR)


15 hop count limit remained.


Rudimentary plain text authentication was added to
secure routing updates; later, MD5 authentication
was defined in RFC 2082.


RIPv2 is specified in RFC 2453

RIPv2 Packet Format

One RIP message can
have up to 25 route entries

1: request

2: response

2: for IP

0…0: request full rou
-
ting table

Address of destination

Cost (measured in hops)

2: RIPv2

RIP Security


Issue: Sending bogus routing updates to a router


RIPv1: No protection


RIPv2: Simple authentication scheme



2: plaintext


password

RIP Problems


RIP takes a long time to stabilize


Even for a small network, it takes several minutes
until the routing tables have settled after a change


RIP has all the problems of distance vector
algorithms, e.g., count
-
to
-
Infinity


RIP uses split horizon to avoid count
-
to
-
infinity


The maximum path in RIP is 15 hops

Thanks