초록 ▼

A router (10) in a packet-based telecommunications system assembles an outgoing packet by inserting between an incoming packet's link-layer and network-layer headers a shim header containing a label that the next-hop router will use as an index into its forwarding table. The shim header also include

A router (10) in a packet-based telecommunications system assembles an outgoing packet by inserting between an incoming packet's link-layer and network-layer headers a shim header containing a label that the next-hop router will use as an index into its forwarding table. The shim header also includes a time-to-live field, and the router determines on a case-by-case basis whether to propagate into that field the value from a corresponding time-to-live field in the incoming packet's network-layer header. Specifically, the router computes the output packet's shim-header time-to-live value by decrementing the result of a bitwise OR operation in which the operands are the network-layer time-to-live value and a switch value that the router fetches from its forwarding-table entry for the incoming packet's destination. This propagates the incoming network-layer time-to-live information into the shim header if the switch value's bits are all logical zeros but not if they are all logical ones.

대표청구항 ▼

[ What is claimed is:] [1.] A label-switching router including:A) reception circuitry that receives electrical signals representing incoming packets of which each includes at least one time-to-live field in a structure that includes a network-layer datagram and an outer header that includes a link-l

[ What is claimed is:] [1.] A label-switching router including:A) reception circuitry that receives electrical signals representing incoming packets of which each includes at least one time-to-live field in a structure that includes a network-layer datagram and an outer header that includes a link-layer header;B) time-to-live circuitry that determines, for each of a plurality of the incoming packets, an output time-to-live value by a process that includes performing a bitwise OR operation between a switch operand and an input operand whose value is determined in accordance with the value in one said time-to-live field in that incoming packet;C) packet-assembly circuitry for constructing, for each of the plurality of the incoming packets, a respective output packet associated therewith whose outer header includes a shim header, located between the link-layer header and the network-layer datagram, that includes a stack-entry sequence comprising at least one more shim-header stack entry than the incoming packet with which it is associated, at least the top shim-header stack entry including a time-to-live field containing the output time-to-live value determined by the time-to-live circuitry; andD) output circuitry for transmitting the outgoing packets thus constructed.