IBM 9077 manual IP Protocol, Data Forwarding, Route Table Implementation

Manager updates the system routing tables and performs other administrative functions, the intelligent processors on each media card perform all routing functions. This design supports efficient distributed processing of router operations.

2.2.1 IP Protocol

The GRF supports IP datagram routing between major types of standard media. The implementation conforms with IP Version 4 and routing specifications described in Internet RFCs.

Each media card has a complete set of route and Address Resolution Protocol (ARP) information contained in the program memory space of the card’s on-board processor. IP packets are buffered in large transmit and receive buffers from which they are transmitted across the central switch fabric to the destination media. Any difference in MTU size (large MTU to smaller MTU) is handled by packet fragmentation as specified in the IP standard. Logic on the destination media is responsible for any media-specific processing of the packet, such as producing 53-byte cells for ATM.

Data Forwarding

Individual media cards maintain their own route tables, perform lookups, and autonomously handle the passing of datagrams to other media cards for export, without intervention of the Router Manager. Layer-3 decisions are local to each card.

Route Table Implementation

Critical to providing sustained performance in a highly dynamic environment are the cacheless route table and route lookup implementation. Each card carries a complete copy of the route table and can support up to 150,000 entries.

Keeping pace with significant advances in routing, the GRF also supports variable-length subnet masking and route aggregation.

Router Node 19