Hi all,
Please tell me how can I differentiate ospf and is-is ?
Am planning to do my dissertation on this. Thank you.

Your choice depends on the hardware in your infrastructure. Take a look at this CiscoNET article.

CiscoNet.com - ISIS VS. OSPF (http://www.cisconet.com/index.php/ISIS/ISIS-VS.-OSPF.html)

Also, http://geocities.com/mnvbhatia/draft-bhatia-manral-diff-isis-ospf-00.txt