Nortel Networks Corporation

Van A Hunter

Milan Momirov

Joseph M Regan

Alfred Nothaft

Akhil Duggal

Rajesh Gopal Nair

Sri Reddy

Tissa Senevirathne

Somasekhar Potluri

A method and apparatus is described which pertains to load sharing/trunking in a communication device used in unicast and/or multicasting interchange of information. A plurality of available ports in the interface cards of the device is identified. More than one port is selected to be configured as a Multi-Link Trunk (MLT) even through the ports may be located on different interface cards.

Load sharing/trunking in a communication device

A method and apparatus for efficiently performing a longest match search are provided. According to one aspect of the present invention, an entry in a forwarding database, a routing table, or the like is located using an improved longest match search. A mask is applied to an address, such as a destination Internet Protocol (IP) address, to determine a masked address that is to be used for purposes of locating a matching entry in the forwarding database. The forwarding database is searched for an entry that matches the masked address. Subsequent masks are produced by performing an address-sensitive decimation of the former mask. For example, the former mask may be shortened based upon the location of the least significant bit containing a one in the masked address. According to another aspect of the present invention, data forwarding employs the improved longest match search. Data is received at a port. An address is extracted from the data. A forwarding database is searched for a longest match for the address by comparing a portion of the address indicated by a mask to entries in the forwarding database and using progressively shorter masks, determined based upon the masked address, for each subsequent search until a matching entry is located. If a matching entry is found, the data is forwarded to a destination associated with the matching entry.

Longest best match search

A method and apparatus selecting between primary switching fabric in an asynchronous transfer mode (ATM) network includes a Tap Mux controller that monitors the signals being transmitted to each of four fabric access devices. As each of the fabric access devices receives nine communication lines, the Tap Mux controller monitors a total for 36 communication lines on the primary switching fabric. Because the switching fabric is completely redundant, however, the Tap Mux controller also monitors a total of 36 communication lines on the protection switching fabric. The Tap Mux controller, therefore, includes logic that defines 72 state machines that each monitor one of the 72 lines. Each state machine, in the described embodiment, initiates a defined length time window and counts errors therein. Protection path switching occurs, for example, only when 10 errors occur on any one of the 36 primary switching fabric lines being received by four fabric access devices therein within a 100 millisecond window initiated at the detection of the first error on the communication line. If 10 errors are not detected within a defined communication window, in the described embodiment, the window is terminated and is only reinitiated upon the detection of the next line error.

Method and apparatus for switch core health monitoring and redundancy

A method for transporting and aligning data across a set of serial data streams. The method includes creating a predetermined number of data streams from a first data stream. The first data stream has a first predetermined bit width and each data stream of the predetermined number of data streams has a second predetermined bit width smaller than the first predetermined bit width. In addition, the method includes inserting an alignment pattern in each of the predetermined number of smaller data streams. The predetermined number of smaller data streams are combinable into a data stream having the first predetermined bit width based on the alignment pattern. The method also includes preparing the predetermined number of smaller data streams for transmission. An apparatus for performing the method is also disclosed.

Method and apparatus for transporting and aligning data across multiple serial data streams

Automatic load sharing-trunking

A method and apparatus for a media access controller supporting redundant links are provided. According to one aspect of the present invention a media access controller includes a two transceivers for communication with an source and/or destination port. Each transceiver has a receiver and transmitter. When the media access controller sets up a physical link to the desired source and/or destination port each transceiver sets up a separate physical link to the source and/or destination port. One of the physical links is the primary physical link and the other is a redundant or backup physical link. By using two physical links if a failure of interrupt occurs on the primary physical link then a switch-over is performed to use the redundant physical link.

Method and apparatus for a Gigabit Ethernet MAC (GMAC)

A method and apparatus for efficiently searching a forwarding database or similar data structure are provided. According to one aspect of the present invention, the overall average time required to forward a packet from the ingress port of a network device to one or more egress ports may be reduced by attacking the worst case forwarding database search. Data is received at a first port of the network device and a search key is extracted from the data. Typically the search key includes one or more of a source or destination Internet Protocol (IP) address, a souce or destination Media Access Control (MAC) address, and/or a Virtual Local Area Network (VLAN) tag. Ultimately, the data is forwarded to a second port of the network device based upon a matching entry located by the search. The search includes retrieving keys from entries of the forwarding database and comparing the search key to the keys until a matching entry is located. The retrieval includes causing a pipelined memory in which the forwarding database is stored to access memory locations in an order that minimizes a worst case search of the forwarding database. For example, a request is made to load a first key from memory that is associated with a database entry and subsequent requests may be made in a pipelined manner to load subsequent keys, whereby the memory is caused to access keys of different entries during consecutive clock cycles.

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San Jose, CA, United States of America

Van A Hunter