IBM 9077 manual Interoperability, Spanning Tree, Bridge Filtering Table, Fragmentation

4.6.4 Interoperability

The following table gives an overview of the GRFs interoperability features.

FDDIFrame forwarding is compatible with any station sending and receiving FDDI LLC frames.

EthernetFrame forwarding is compatible with any station using either DIX Ethernet or IEEE 802.3 frames.

ATM OC-3cFrame forwarding is compatible with any remote bridge using RFC-1483 bridging encapsulation.

Spanning treeGRF transparent bridging will interoperate with any other bridge (including other GRFs) compliant with the IEEE 802.1d spanning tree protocols.

4.6.5 Spanning Tree

The GRF implementation supports the full Spanning Tree Algorithm specified in the IEEE 802.1d standard.

Using the spanning tree, network topologies can contain cycles that can be used as redundant or backup links. The spanning tree controls the bridge’s flow of traffic over all potential links to prevent packet storms (bridges repeating a packet or packets to each other, without end).

4.6.6 Bridge Filtering Table

Media card bridge interfaces forward new MAC source addresses to the operating system for insertion in the global bridge filtering table that is maintained on the control board. Each bridging media card type (FDDI, Ethernet, and ATM OC-3c) also has a copy of this table.

Bridge interfaces also "age" entries according to a site-specified timeout value. When no activity is associated with a MAC address for the specified timeout interval, the interface sends the operating software a delete request and the address is removed first from the global bridge filtering table and then, via update packets, from the media cards’ tables.

The timeout is specified in seconds in the /etc/bridged.conf file.

4.6.7 Fragmentation

IPv4 frames are fragmented as necessary, as when bridging a FDDI frame of more than 1500 bytes to an Ethernet interface.

144IBM 9077 SP Switch Router: Get Connected to the SP Switch