Bi-directional chaining of network access ports

Network access apparatus, comprising:

• first and second master units, each comprising a physical interface to a packet-switched network;
• a plurality of slave units, each slave unit comprising one or more ports to respective subscriber lines;
• and
• a plurality of physical interface lines, which link the slave units in one or more daisy chains, in which the slave units are mutually connected in series by the physical interface lines therebetween, each daisy chain comprising at least a first slave unit connected by one of the physical interface lines to the first master unit and a last slave unit connected by another of the physical interface lines to the second master unit,
• wherein in normal operation, downstream data packets received from the network are passed from the first master unit to each of the daisy chains via the first slave unit in each chain, and upstream data packets received by the slaves in each chain from the subscriber lines are passed via the first slave unit in the chain to the first master unit for transmission over the network.

Network access apparatus, comprising:

• first and second master units, each comprising a physical interface to a packet-switched network;
• a plurality of slave units, each slave unit comprising one or more ports to respective subscriber lines;
• and
• a plurality of physical interface lines, which link the slave units in one or more daisy chains, in which the slave units are mutually connected in series by the physical interface lines therebetween, each daisy chain comprising at least a first slave unit connected by one of the physical interface lines to the first master unit and a last slave unit connected by another of the physical interface lines to the second master unit,
• wherein each of the first and second master units comprises:
• a switch, configured to route data packets between the respective physical interface and the one or more daisy chains;
• and
• a pre-switch, which in the event of a fault at a location in one of the daisy chains, re-routes at least a portion of the data packets exchanged with one or more of the slaves in the daisy chain in which the fault has occurred through another one of the daisy chains.

Network access apparatus, comprising:

• first and second master units, each comprising a physical interface to a packet-switched network;
• a plurality of slave units, each slave unit comprising one or more ports to respective subscriber lines;
• and
• a plurality of physical interface lines, which link the slave units in one or more daisy chains, in which the slave units are mutually connected in series by the physical interface lines therebetween, each daisy chain comprising at least a first slave unit connected by one of the physical interface lines to the first master unit and a last slave unit connected by another of the physical interface lines to the second master unit,
• wherein each of the slave units comprises:
• a switch fabric comprising one or more switches, which convey data packets to respective ports on the switch to which the packets are addressed;
• and
• a pre-switch, which receives the data packets from one of the physical interface lines connected to the slave unit and passes those of the data packets that are addressed to any of the ports on the slave unit to the switch fabric, while passing packets not addressed to any of the ports on the slave unit for output through another of the physical interface lines.

In a network access multiplexing system, in which a master unit is connected by a physical interface to a packet-switched network, a slave unit configured to be coupled to the master unit in a daisy chain of such slave units, the slave unit comprising:

• a plurality of ports, for coupling the slave unit to respective subscriber lines;
• first and second physical interfaces, coupled to exchange packets with preceding and succeeding units, respectively, along the daisy chain;
• a pre-switch, coupled to receive packets from the first physical interface and responsive to address data carried by the packets, to sort the packets such that packets addressed to the slave unit are retained, and packets addressed to the succeeding units are passed to the second physical interface;
• and
• a fabric of one or more switches, which convey the retained packets to the ports, responsive to the address data.

A method for providing access to a network, comprising:

• coupling first and second master units to interface with the network;
• linking a plurality of slave units, each slave unit comprising one or more ports to respective subscriber lines, in a daisy chain between the first and second master units;
• conveying initial downstream data packets, received from the network by one of the master units, along the daisy chain in a first direction, so as to deliver the packets to the ports of the slave units;
• and
• in the event of a fault in the daisy chain, conveying further downstream data packets, received from the network by one of the master units, along the daisy chain in a second direction, opposite to the first direction, so as to deliver the further packets to the ports of at least some of the slave units.