ospf-lite draft-thomas-hunter-reed-ospf-lite-00.txt Matthew Ramon Thomas mrthom@essex.ac.uk

1. ospf-litedraft-thomas-hunter-reed-ospf-lite-00.txtMatthew Ramon Thomasmrthom@essex.ac.uk 70th IETF Meeting

2. ospf-lite features at a glance • Branch version of OSPF (OSPF’s baby brother) • Avoids design phase. • ‘Instant on’ for customers with no configuration if required. • Vendors can sell direct to client for large networks. • Simple single area concept • Support for external routes LSA 5’s / Opaque LSAs • The ability to ‘boot up’ (2 stage) over non fully meshed multi-access network. • MPLS core: Service Providers can implement a simplified OSPF protocol on growing MPLS clouds without resorting to IS-IS. 70th IETF Meeting

3. Method Overview: 5 major Adaptations • A single unified link type within the LSA 1 was introduced for all network types • Hello protocol reworked to allow neighbor establishment over non fully meshed media • A single LSA type is used to describe the router • Designated router is no longer required • Multiple instances solution to area LSA complexity 70th IETF Meeting

4. A single link type for ospf-lite • ospf-lite employs a single link type within the LSA 1 • ospf-lite treats all networks as ospf-lite-stub or ospf-lite-transit • So it’s independent of the underlying network medium • For NBMA networks ospf-lite still compensates: • Uses MIB IF lookup, recognises NBMA interface and; • Additional 32 bit route still added for NBMA networks • This is automatic • OSPF P2MP, P2P, Broadcast, NBMA types removed 70th IETF Meeting

5. Promiscuous Hello Protocol • Always on, all networks treated the same. • This allows ospf-lite to ‘boot up’ over non fully meshed NBMA networks. 70th IETF Meeting

6. Promiscuous Hello protocol cont.. • An ospf-lite router may see neighbors listed in another router’s Hello. • ospf-lite Hello then attempts a unicast Hello to connect to that neighbor. • This may fail until routes are established between the directly communicating neighbors, but the protocol remains promiscuous and establishes communication when the routes are in place. 70th IETF Meeting

7. LSA type reduction • All of the data required to build the calculation graph is carried inside the Router LSA 1. • V2 has duplication in the LSA 2 due to the DR function • ospf-lite has a single LSA type (Router LSA 1) to describe the router itself. • External LSA 5s are supported • Opaque LSA 9,10,11 are supported 70th IETF Meeting

8. DR Removal • DR function originally designed for IS-IS with more active ES. • ospf-lite removes all of the LSA 2’s. • Each LSA 2 is flooded throughout the whole area in OSPF V2 • If each router has an Ethernet, then the number of LSA 2’s could equal the number of router LSA 1s • The removal of these LSAs is a significant simplification 70th IETF Meeting

9. Adjacencies on shared media are are now O(n2) • This is by design. • OSPF V2 avoids O(n2) but ospf-lite uses O(n2) when prudent 70th IETF Meeting

10. O(n2) concerns: linear • With ospf-lite and V2; when routers are added to an internet; • LSA Traffic on an simple P2P internet does not increase O(n2) but increases linearly; • Adjacencies on an P2P internet do not increase O(n2) • Each router generates it’s own LSAs • These of course are copied by each router and distributed linearly • LSA Traffic DOES increase as O(n2) on a broadcast or fully meshed network with no Designated Router function. Adjacencies also increase O(n2) • What is n? • For n to become large the number or routers on an individual network would have to be large. • A high number of nodes in a standard P2P cloud, each on their own Ethernet connection equates to an n of 1 • Five routers sharing an Ethernet equates to an n of 5 70th IETF Meeting

11. O(n2) concerns cont.. • Today’s networks are largely point to point or have few routers on a single network / VLAN / PBT path so n is low. • Ethernet comprises of multiple VLANS • Frame clouds are often configured point-to-point 70th IETF Meeting

12. Areas / Multiple instances • Areas were originally conceived to summarize the database • Although they can summarize routes, this is normally achieved by manual configuration due to class addresses being split between areas. • The areas do summarize the database. • Video graphics programmers regularly run SPF on huge databases. • Areas do succeed in shielding devices from routes 70th IETF Meeting

13. Multiple Instances • ospf-lite employs multiple instances with route redistribution where legacy areas are required. • There is no theoretical limit to size of ‘area’. • With multiple instances and redistribution there is no defined limit to AS size. • BW utilisation is low so we are only limited by processor power and memory. 70th IETF Meeting

14. IANA / WG Considerations • We would like to use Version number zero? • This was never registered with IANA but its up to the Working Group to decide… 70th IETF Meeting

15. Thank you You know you could have half a cup of regular coffee, but is it equal to a large skinny Latte? 70th IETF Meeting