3com Corporation

Hewlett-packard Development Company, L.P.

3com Technologies

Hewlett-packard Company

Kam Choi

Edele O'Malley

Eugene O'Neill

Gareth Edward Allwright

Patrick Gibson

Christopher Hay

Jerome Nolan

Bryan J Donoghue

David J Law

Paul J Moran

John F Hickey

Kevin Jennings

Maurice A Goodfellow

Quang T Tran

Daniel M O'Keeffe

Kevin Loughran

Vincent Gavin

Francisco Aquino

Richard A Gahan

Raymond Beechinor

Tin Lam

Fergus Casey

Maunte A Goodfellow

Ray Beechinor

Maurice Arthur Goodfellow

In one embodiment, a method is described for detecting an operational failure between the network unit and an adjacent network unit in the stack; controlling the switching engine to redirect packets which would otherwise be sent from a particular port to the adjacent network unit to be forwarded from another port to be sent to a different network unit in the stack; and entering the switching engine into a bypass mode in response to control data indicating an operational failure between at least two other network units in the stack to cause packets to be forwarded without being re-directed by the switching engine.

Cascade system for network units

A network stack includes a plurality of network units each of which includes a multiplicity of ports for receiving and forwarding addressed data packets, at least two cascade ports and a switching engine for forwarding received packets to at least one port in accordance with address data in the packets and a cascade connection including, for each of two opposite directions around the stack, at least one unidirectional path for data packets composed of links each between a respective cascade port on a network unit and a corresponding cascade port on the next network unit.

A cascade system of network units includes forwarding units which have external ports, a communication fabric connecting the units and at least one processing unit which needs no forwarding database. The processing unit may perform a security operation such as intrusion prevention or encryption. Each forwarding unit on receipt of a packet performs a look-up to determine an egress port, to determine whether the packet must be diverted to a processing unit, to provide the packet with a first forwarding instruction identifying the egress port uniquely within the system and a second forwarding instruction identifying a diversion port by which the packet can reach the processing unit and to set an order field which determines which of the forwarding instructions shall be performed first. The processing unit is operative on receipt of the packet by way of the diversion port to change the order field to specify that the packet should now be sent to the egress port.

Packet diversion in switching fabrics and multiple forwarding instructions for packets

A method performs a lookup on a search key word, employing a trie database including multiple trie blocks that include pointers to other trie blocks. Each trie is accessible by means of a segment of the search key. A selected section of the search key word is applied to a content addressable memory. In the event of an absence of a match of the selected section with an entry in the content addressable memory, a trie search is performed on the whole search key word. In the event of a match of the selected section with an entry in the content addressable memory, a partial trie search is performed, commencing with a first segment of the search key word after the selected section that has been matched in the content addressable memory.

Trie search engines and ternary CAM used as pre-classifier

A multi-port network unit for use in a cascade system of network units sends from a cascade port a packet including a special header having a source port ID, a destination port ID and a 'destination port known' field. The port IDs identify both a unit and a port within a unit. A routing database is set up, optionally by a discovery protocol, in terms of ports and either destination units (within the cascade) or source units (within the cascade). The database includes a mesh table, indicating from which cascade port a packet with a known destination port ID should be forwarded, without needing a fresh look-up. The database also includes a multicast exclusion table which allows ingress of packets with source unit IDs matched to an ingress port. The scheme allows a general mesh type of cascade while dynamically preventing closed loops.

Network units for use in and organisation of cascade systems

A rules engine for the examination of selected fields in an addressed data packet has an access control list table of which the entries each define an access control list rule, an action and a chain identifier. The access control list rule may be a basic rule which refers to network addresses and transport layer port numbers. The rules engine also has an extension rule table of which the entries each define an extension rule, a respective action and a respective rule identifier. The extension rule may refer to a particular TCP flag. When a packet arrives, the engine searches both tables. This search is made independently of the ordinary network layer or link layer address lookup. If there is a match in both tables, and the chain identifier matches the extension rule identifier, the rules engine prescribes the action associated with the extension rule. If the chain identifier of a matched access control list rule does not match a rule identifier of a matched extension rule the rules engine prescribes the action associated with the basic rule. In the absence of a match with any access control list rule the action on a packet is based on the result from the ordinary address lookup.

Rules engine for access control lists in network units

A system of switch modules contains input demultiplexers connected to ports on each of the modules and output multiplexers connected to each of the modules. Each module has output and input interfaces for mesh links and at least one output interface is looped back to an input interface on the same module. The arrangement reduces module-to-module traffic and corresponding increases the transmit bandwidth of a module.

High-speed switch architecture

A switching module has external ports for sending and receiving data packets and mesh interfaces for internal mesh connections with other modules. A switching engine directs packets to one or other of the mesh interfaces according to the port number of a 'destination' or egress port on another module, as determined by a lookup. The port numbers are programmable so that the distribution of traffic through the mesh connections can be modified.

Switch module architecture

Network units such as switches for use in a cascaded stack are organised to provide a cascade connection in the form of a dual unidirectional connection so that, in its ordinary configuration, there is at least one and preferably more than one unidirectional ring for each direction around the cascade, each ring including a respective port on each unit. For each ring, each port on a unit is connected by a respective link to a corresponding port on the preceding unit and the following unit. The units provide a self-healing operation in the event of various kinds of operational failure. The self-healing operation includes loop-back of packets in units adjacent the failure and bypass of a packet switching process for other units. The units include control logic for passing control frames containing status information relating to the units and links between them and for co-operation with a CPU to control a switching engine to perform the self-healing operation in accordance with that status information. The units forward on the cascade packets with headers that identify a destination port and the unit on which that port is located and also indicate which units have and have not been traversed by a packet.

Cascade control logic for use in a switch or other network unit that can be used in a cascaded stack can maintain normally a point-to-point half-duplex connection for control data with each of the next preceding and next succeeding units in the cascade. Each cascade logic device is organised so that for one direction, conveniently called the up direction, a device is a master and in the other direction the device is a slave in respect of the control path. A control device will generate master control frames in the up direction and deliver slave control frames in the down direction. The control device is organised so that in the absence of reception of valid control frames on a control link control data which would otherwise be sent out on that link is looped back within the control device. In this manner the control device can maintain under normal circumstances two virtual control channels which can 'self-heal' notwithstanding the failure or powering-down of a unit in the cascade. Status information represented by the control frames can be used to control a switching engine to provide self healing of the data path in the cascade.

Cascade control system for network units

A detector for determining which interface protocol is in use by a serialiser/deserialiser, and comprising detecting channels composed of clocked delays and bit comparators for detecting the presence of idle signals coded according to either ten-bit or five-bit protocols using either one or two clocks.

Automatic detector of media interface protocol type

A FIFO store for data packets and their respective status words includes space for the writing of a predetermined sync word or one of a cyclic sequence of predetermined sync words with each status word. The sync word can be used to prevent forwarding of a packet and as an aid to fault diagnosis if on reading the status word the sync word does not match any of the predetermined sync words.

FIFO storage including pointer misalignment detection

Trunking or other relationship is defined between ports on different devices in a cascade-connected stack of network devices. When network communications are passed via the cascade connection an indication is included of whether it originated from a port that is part of a trunk and thereby port-mismatch errors can be avoided.

Trunking in stacked communication devices

A network device incorporating selective compression of stored data packets is disclosed. The network device receives, stores and forwards data packets and includes a system for applying a compression algorithm to packets after their header portions and storing the partially compressed packets, which are decompressed after readout from storage and before they are forwarded. Lengths of a packet as received and as subject to the compression algorithm are compared to prevent storage when the algorithm fails to produce a shorter packet.

Network device incorporating selective compression of stored data packets

A network switch includes a plurality of receive ports for receiving addressed data packets and a plurality of transmit ports for forwarding the addressed data packets and structure responsive to data in said the packets for directing received packets to the transmit ports. In respect of at least one of the transmit ports the switch includes an output buffer for storing data packets before they are forwarded from the port and an allocation controller. The allocation controller allocates each packet destined for the buffer and each packet leaving the buffer for the port into at least one of a plurality of categories, which may be based on priority or protocol data and may define traffic types such as video or audio. For each of the categories there is an allocation register for defining a respective selected proportion of the memory space of the output buffer and structure for accumulating a running total of packet sizes, the total being reduced by the size of each packet in the respective category and leaving the buffer for the port. A packet is discarded when the running total of packet sizes for packets of the same category exceeds the respective proportion of the memory space defined in the respective allocation register. The organization of the switch allows the allocation of a minimum bandwidth for each of the categories.

Growing community of inventors

Tring, United Kingdom

Kam Choi