Unanswered Question
Mar 16th, 2009
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why there is variation in the usage of IGP (ospf/is-is) among ISPs. why some ISPs are using IS-IS while others use OSPF ?

what are the issues related to this ? whether management issues(cost, maintanance) or design issues(scalability, security)?

please tell me in detail.

thank you.

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Harold Ritter Mon, 03/16/2009 - 18:05
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ISIS came out first followed by OSPF. Some ISPs were already running ISIS when OSPF came out and some others decided to go with the relative maturity of former when the latter came out.

There is advantages and disadvantages for both. I personally like ISIS as I feel you can scale it better without requiring to split your core in multiple levels (area in the OSPF terminology). For instance ISIS allows you to only advertise the Loopback interface IP address for each router (not yet available in OSPF). The other link prefixes can then be carried in BGP.

ISIS is also relatively easy to extend to support new protocols (Address Families) as only the addition of one or more TLVs (Type, Length, Value) is required.

OSPF on the other hand has more features and knobs to fine tune and adapt to a given network as it is widely used in the enterprise world.

Bottom line today is what protocol one feels most comfortable with.


Yasir Ashfaque Thu, 03/26/2009 - 10:01
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Yes My Vote is too with IS-IS, cause i have some bad experiences with OSPF.

jai231555 Sat, 03/28/2009 - 01:48
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can you please explain some of your bad experiences with OSPF. your will be really appreciated.

thank you.


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