摘要:
In a stack of network units each includes a multiplicity of ports for receiving and forwarding addressed data packets and a forwarding engine which in response to address data selects at least one port for the forwarding of a data packet. A cascade connects the units and allows the transmission of a packet placed on said cascade by a unit to all the other units. Each unit is responsive to a packet received from the cascade to forward or discard the received packet according to predetermined forwarding rules. A trunk includes a respective port of each of some but not necessarily all the units. Each unit includes a ‘trunk box member’ register indicating which of the units has at least one port connected in the trunk When a first unit in the stack receives, at a port connected neither to the trunk nor the cascade, a packet destined for the trunk, the first unit directs that packet to a port connected to the trunk if the first unit has such a port and otherwise sends that packet to the cascade. When a second unit in the stack, having a port connected to the trunk, receives by way of the cascade from the first unit a packet destined for the trunk, the second unit determines with recourse to the forwarding rules, data identifying the first unit and the respective register whether to forward said packet to the trunk. The invention is particularly intended for use in stack-wide trunks operating according to ‘local forwarding’ and ‘next-in-line’ rules and allows units in the stack to be omitted from direct connection to the trunk.
摘要:
A network switch comprises a multiplicity of ports for receiving and forwarding addressed data packets, a forwarding engine for directing packets received at the ports to at least one other port, a register for storing unit identifications of a set of units including the network unit, and hashing logic for selecting one of the unit identifications in response to address data in a packet. The forwarding engine makes a determination whether the one of the unit identifications corresponds to the network unit and is operative to direct the packet in accordance with that determination. The use of the register enables a substantial increase in the number of ports that can be members of a stack-wide trunk.
摘要:
A trie searching technique employs entries each including a pointer to the next block in the search and a status indication and also including start and end indexes which define a selected section of the trie key identifying an entry within the block identified by the pointer. Thereby the program for selection of the search key is defined by the trie entries themselves, enabling a general variety of search selections and jumps to avoid any unnecessary parts of the trie search key.
摘要:
A method and switch for controlling the allocation of priority of TCP packets, more particularly for distinguishing between data and control packets and assigning an increased priority to control packets. The layer 4 information in the form of the flag bits of the header are snooped in the switch to determine whether any flag other than PSH is set and if so to allocate a priority to that packet, which will usually be a higher priority than data packets.
摘要:
A stackable multi-port communication device for a packet-based data communication system, having a multiplicity of physical ports for the reception and dispatch of data in the form of packets, includes switch logic for selecting for a packet at least one destination selected from a multiplicity of ports which include a logical port common to a specified group of said physical ports. A cascade trunk logic, coupled to the switch logic, is used for determining, for the dispatch of a packet directed to said logical port, a selected port of said group of said physical ports; and a remote monitoring logic is used for forwarding a copy of the packet. The remote monitoring logic stores an indication of all the physical ports on the unit from which the copy may be forwarded by the remote monitoring logic and prevents the forwarding of the copy of the packet to any physical port which corresponds to the port selected by the cascade logic for the dispatch of said packet, whereby a packet which is forwarded from any of the specified group of physical ports is not duplicated by the remote monitoring logic.
摘要:
In a stack of multi-port network communication units each unit has a forwarding database, the units are connected by way of a cascade, and at least some of the units are connected to links constituting a trunk. When a unicast data packet is received at a first of said units and the unicast data packet has a destination address which is not the subject of an entry in the forwarding database of the first unit, the unicast data packet is sent by way of the cascade to the other units in the stack, accompanied by a flag. When a second unit has in its forwarding database an entry, associating the destination address with forwarding data, it sends a management packet indicating said destination address and the identity of said second unit, so that the database of the first unit can be immediately updated.
摘要:
A multiport network device includes a multiplicity of receive queues, a multiplicity of transmit queues and a forwarding engine for transferring entries from the receive queues to the transmit queues. When a transmit queue is greater than a first hysteresis point, the forwarding engine prevents transfer of entries from a receive queue to the transmit queue and transfer of entries to the transmit queue is allowed when the length of the transmit queue falls below a second hysteresis point.
摘要:
A multi-port data communication device includes a common central memory through which all data packets must pass. Packet data is written to and read from the common memory space in bursts in response to receive write requests and transmit read requests. A transmit read request for a first burst of data in a packet has in a central arbiter a relatively low priority and transmit read requests for a second and any subsequent burst of data in a packet have in the central arbiter a relatively high priority. Preferably the receive write requests have in said central arbiter a priority intermediate said relatively low priority and said relatively high priority. The priority system reduces the likelihood of underrun and overrun particularly when the burst size is generally smaller than the packet size.
摘要:
An Ethernet data packet including a VLAN tag header and a VLAN identification field is modified. The modification is accomplished by inserting in place of the VLAN tag header a field of the same size including selected information. The VLAN identification may be retained. The inserted field may include a first field indicating the presence of the VLAN identification field and a second field of selected information, the second field being longer than the first field.
摘要:
A network switch which can perform in respect of addressed data packets source address and destination address look-ups in a forwarding database includes a control which inhibits the performance of source address look-ups if the length of a respective receive queue of packets is greater than a threshold. The inhibition may endure until the length of the receive queue falls below a second threshold lower than the first. The inhibition may not be applied if the respective receive queue is subject to head of line blocking