OSPF :
It was developed because of in demand in the internet society to launch a high functionality non-proprietary IGP for the TCP/IP protocol community.
The OSPF is an intradomain routing protocol and is based on link-state routing technology. It has introduced some new concepts that are authentication of routing updates, variable-length Subnet masks (VLSM), root summarization, etc.
IS-IS :
Intermediate System to Intermediate System is a standardized link-state protocol that was developed to the definitive routing protocol for the OSI Model.
IS-IS is a Link-state IGP. Link-state protocols are distinguished by the circulation of the information required to build a complete network connectivity map on each participating router. This map is then used to calculate the shortest path to destinations.
It is predominantly used in ISP environments.
S.No. | Parameter | OSPF | IS-IS |
1. | Administrative Distance | 110 | 115 |
2. | Standard | RFC 2328 (OSPFv2). | ISO 10589, RFC 1195. |
3. | Operating OSI Layer | OSPF operates on the top of the IP layer. | IS-IS operates over L2. |
4. | Virtual Links Supported | Yes | No |
5. | DR/BDR Election | OSPF elects a BDR and DR on broadcast networks. | IS-IS elects a single DIS on broadcast networks. |
6. | IP Connectivity | OSPF Requires IP Connectivity between the routers to share the routing information. | IS-IS doesn’t require IP connectivity between the routers as updates are sent via CLNS instead of IP. |
7. | Support | OSPF supports NBMA and points to multipoint links. | IS-IS doesn’t support it. |
8. | Router Area | OSPF routers can belong to multiple areas. | IS-IS router can belong to only one area. |
9. | Area/Level Types | Backbone Area Standard Area (Non-Backbone Area) | Level 1 Level 2 Level 1/2 Areas |
10. | Security | Prone to attack and hence requires more security overheads for protection. | Since IS-IS runs on level2, hence every unlikely possibility of attack. |
11. | Identification | OSPF uses a Router id to identify a router on the network. | IS-IS uses System ID to identify a router on the network. |
12. | Flexibility | Less Flexible than IS-IS. | More Flexible to use than OSPF especially in the provider domain. |
13. | Table Refresh | OSPF refreshes the entire routing table after 30 minutes. | IS-IS doesn’t refresh the entire SPF Table Periodically like OSPF. |
14. | Related Terms | Area, Non-Backbone Area, Backbone Area, ABR, ASBR, Host. | IS, Level 1, Level 2, L1/L2, Subdomain, ES. |
| 15. | Routing Protocol Preference | 10 | 15 |
