What is round robin routing?

Unanswered Question
Apr 20th, 2010

Hi,

I've heard about RIP, IGRP, EIGRP, OSPF, BGP, IS-IS and FRAME RELAY routing but never heard about round robin routing. I've had google about this but not come up with anything related. I would appreciate if anyone could explain what is round robin routing.

Reference:

http://homepages.uel.ac.uk/u0223755/Routing%20protocols.htm

http://hubpages.com/hub/Types-of-Routing-protocol

Many thanks in advance

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Giuseppe Larosa Wed, 04/21/2010 - 00:03

Hello Adam,

we can speak of round robin forwarding that is when multiple paths exist to reach a destination and per packet load balancing is used.

So round robin routing can be seen as process switching of packets.

Recent CEF implementations allow to perform per packet load balancing without a need to disable CEF (that is forwearding optimization technique used on Cisco routers and multilayer switches in SW on the first ones  with the help of dedicated hardware on the second ones )

Standard CEF use per flow load balancing: given a flow with a specific SA and specific IP DA the same path is used for all packets classified on this flow.

per packet load balancing sends the subsequent packets of the same flow ( IP SA, IP DA) on the different paths and this is a round robin packet forwarding.

if there are three links:

packet n.1 goes out link 1

packet n.2 goes out link 2

packet n.3 goes out link 3

packet n. 4 goes out link1

and so on

see

http://www.cisco.com/en/US/tech/tk827/tk831/technologies_tech_note09186a0080094806.shtml

Then, in other contexts like server load balancing again round robin load balancing can be used in this case each new client TCP connection to the virtual IP address is "routed" to a different real server.

Hope to help

Giuseppe

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