Digital Equipment Corporation

Digital Equipment International Limited

Cabletron Systems, Inc.

Ian M Shand

John A Harper

Anthony G Lauck

Christopher William Gunner

Radia Joy Perlman

John Anthony Harper

Steven Richard Welch

A new packet filtering system associates domain identifiers with respective sets of addresses. A set of domain prefixes defines the set of addresses associated with a given domain identifier. Domain prefixes are found matching the source address and destination address of each received packet. These prefixes are associated with a source domain identifier and destination domain identifier respectively. The system similarly associates sets of one or more protocol types and port ranges with respective protocol domain identifiers. The protocol type, source port and destination port of the received packet determine source and destination protocol domain identifiers for the received packet. The system includes a filtering matrix including one or more entries, each indicating whether an associated received packed should be filtered. The source domain identifier, destination domain identifier, and source and destination protocol domain identifiers are used to index into the filtering matrix, for example using each as an index into one of the dimensions of a four dimensional array used to implement the filtering matrix. In an alternative embodiment, the source and destination protocol identifiers are used to obtain a protocol index from a protocol vector data structure. The protocol index, source domain identifier and destination identifier are then used to index into a three dimensional filtering matrix. The system further optimizes the filtering matrix for size, and the lookup time is dependent only on the number of filtering domains, and not the complexity or number of filtering rules.

Fast network layer packet filter

A method of transferring foreign protocol information across a hierarchical backbone network is disclosed. The hierarchical backbone network operates according to a first protocol and includes multiple areas, some of which have a destination that operates according to a second protocol. Additionally, each area has at least one router located therein. The locations of the destinations in each area are identified to the router in that area. Information that identifies the locations of the destinations in each area is transferred to a router in each of the other areas regardless of whether the destinations are located in the same area as the router. Finally, information formatted according to the second protocol is transferred among any of the destinations.

Method for supporting foreign protocols across backbone network by

A node operating in a network using the International Standard Organization (ISO) High-Level Data Link Control (HDLC) network protocol includes a mechanism for encoding information such that frames including the encoded information can be correctly interpreted by nodes operating in either of the standard 16-bit or 32-bit ISO-HDLC operating modes. The encoding mechanism produces a preliminary frame check sequence by encoding the information in an encoder using a generator polynomial G.sub.48 (x), which is a combination of the generator polynomials G.sub.16 (x) and G.sub.32 (x) which are used to produce frame check sequences for nodes operating in 16-bit or 32-bit modes, respectively. Before the information is encoded, the encoding mechanism sets the encoder to an initial condition using an initializing polynomial I.sub.48 (x). The preliminary frame check sequence is further encoded by adding to it a complementing polynomial C.sub.48 (x). The result is a 48-bit frame check sequence. The encoding mechanism appends the 48-bit frame check sequence to the information, and transmits the information and the appended 48-bit frame check sequence over the network as part of a frame.

Method and apparatus for generating a 48-bit frame check sequence

A communication network consists of end units (EUs) and distribution units (DUs) coupled together by links which may include local area networks (LANs). The units maintain neighbor tables by sending out Hello messages which indicate the unit type and contain the network service access point (NSAP) IDs or addresses of the units. Data messages (packets) mainly originate and end at EUs. An EU maintains only partial routing information about neighbors, while the DUs collectively maintain complete information about all NSAPs. So if an EU wants to send a packet to an EU which is not a neighbour (and sometimes even if it is), it need merely send it to a neighboring DU; that DU, along with the other DUs, must find a route to the destination EU. This invention provides a hybrid unit (HU), which acts as a DU to EUs but as an EU to DUs. The HU provides DU-like message forwarding but only on a local basis within a subnetwork of EUs and HUs.

Growing community of inventors

Cobham, United Kingdom

Ian M Shand