Monday, January 18, 2010

BGP Path Vector Characteristics


I spent my morning learning about BGP and its path vector technology. Path Vector is like an updated scalable version of distance-vector routing. However it has one main difference than any other distance-vector or IGP. BGP doesn't use broadcasts or multicasting since it uses TCP as it's transport protocol. TCP is used because it's able to send a large amount of data reliably, the BGP table has over 190,000 entries in the full routing table currently! This size would actually be in the millions but thanks to technologies such as CIDR, the table size has been reduced considerably. Since BGP doesn't use any type of broadcasting mechanism, an AS being use to transit BGP routes between other AS's must be fully meshed within the transit AS. In other words every router running BGP in a transit AS must be seen by every other BGP router in that AS. this is becuase the BGP updates are sent as unicast messages which aren't forwarded in a multicast manner i.e. one-to-one mesages.

CCNA Configure the Network free lab book is on the way soon! I should be completed with all of the labs for this eBook by sometime next week. I will also need my work to be edited for the final version as well. If you haven't already please subscribe to the mailing list on the right to be the first to receive updates and a link to download the free CtN CCNA lab book!

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