3com Corporation

Synernetics Inc.

Christopher P Lawler

Stephen L Van Seters

Shannon Q Hill

Stephen A Hauser

David C Ready

R Bruce McClure

Mark A Sankey

David Lipschutz

John A Flanders

Robert Millard France

Thomas A Radogna

A method and apparatus for receiving and transmitting network frames via an internetworking device, in which a first portion of a total number of buffers is allocated among port-dedicated buffer pools, and a second portion is placed in a common pool accessible by any of the network ports. A frame is received at a first port, and a list of buffers accessible only by that port is referenced to identify buffers not already in use. A second list of buffers in the common pool is referenced to identify unused buffers for use if insufficient unused buffer space is available in the port-dedicated buffer pool. Frame data is then stored in the identified buffer(s). Upon retransmission, the buffer(s) used to store the. transmitted frame is released to the port-dedicated and/or common buffer pool(s).

Method and apparatus for internetworking buffer management

A method and cache management for a bridge or bridge/router providing high-speed, flexible address cache management. The unit maintains a network address cache and an age table, searches the cache for layer 2 and layer 3 addresses from received frame headers, and returns address search results. The unit includes an interface permitting processor manipulation of the cache and age table, and supports a 4-way set associative cache to store the network addresses. A plurality of functions implemented in hardware enables software manipulation of the associated cache. Four cache operating modes are selectable. The unit can identify and select destination ports within a Load Balanced Port Group for frame forwarding. The unit utilizes Virtual LAN identification in conjunction with a MAC address for lookup in the cache. A cyclic redundancy code for each address to be looked up in the cache is used as an index into the cache. If a cache thrash rate exceeds a predetermined threshold, CRC table values can be rewritten. Four time-sliced cache lookup units are provided, each consisting of a cache lookup controller for comparing a received network address to an address retrieved from an identified cache set.

High speed cache management unit for use in a bridge/router

A method and apparatus for receiving and transmitting network frames via an internetworking device, in which a first portion of a total number of buffers is allocated among port-dedicated buffer pools, and a second portion is placed in a common pool accessible by any of the network ports. A frame is received at a first port, and a list of buffers accessible only by that port is referenced to identify buffers not already in use. A second list of buffers in the common pool is referenced to identify unused buffers for use if insufficient unused buffer space is available in the port-dedicated buffer pool. Frame data is then stored in the identified buffer(s). Upon retransmission, the buffer(s) used to store the transmitted frame is released to the port-dedicated and/or common buffer pool(s).

An address management circuit and method of operation, for use in a communications internetworking device, includes a search engine having first and second search circuits for concurrently searching a network address table for source and destination addresses of a frame received by the communications internetworking device. Memory read cycles of the source and destination address searches are interleaved to allow a memory access to occur during every system cycle to thereby rapidly complete the searches for both the source and destination addresses.

Apparatus and method for processing data frames in an internetworking

A method and apparatus for increasing the throughput of a communications internetworking device using concurrent reception and transmission of data packets. The method involves the beginning of a retransmission by the communications internetworking device, to a destination network, of a frame undergoing reception by the communications internetworking device, from a source network, prior to the completion the reception of the frame from the source network by the communications internetworking device.

Method and apparatus for the concurrent reception and transmission of

A network interface for connecting a first network utilizing a first medium access control protocol to a plurality of relatively slower networks utilizing a second medium access control protocol. The network interface includes memory in which a table of addresses of nodes on the plurality of second networks is maintained. The network interface passes data from a data packet received from the first network to one of the plurality of second networks only if the destination address of the data packet matches one of the node addresses within the table of node addresses. The network interface passes data from a data packet received from one of the plurality of second networks to the first network only if the destination address of the data packet does not match a node address in the table of node addresses. The network interface passes data from a data packet received from one of the plurality of second networks to another of plurality of second networks only if the destination address of the data packet matches a node address in the table of node addresses.

Network multiplexer

An internetworking device providing enhanced packet header translation for translating the format of a header associated with a source network into a header format associated with a destination network of a different type than the source network. The device includes a memory for storing an address portion of a received packet header in a first block of buffer locations and the remainder of the received packet in a second block of buffer locations, spaced from the first block of buffer locations by a gap. The gap permits supplemental header information to be written into the buffer when necessary for translation. The device further includes a split memory, having an SRAM portion and a DRAM portion allocated to each buffer, with at least the address portion of a received packet and the gap located in the SRAM portion, so as to optimize the translation performance of the device.

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Wellesley, MA, United States of America

Christopher P Lawler