Cisco Technology, Inc.

Robert Goguen

Carol Etta Iturralde

Jean-Philippe Vasseur

Anna Charny

Pawel Piotr Sowinski

David Delano Ward

Ali Sajassi

De Fu Li

Ijsbrand Wijnands

Stefano Benedetto Previdi

Frank Brockners

Muthurajah Sivabalan

George Swallow

Alon Shlomo Bernstein

Alton Lo

Tong Liu

David Richard Barach

Ashok Narayanan

James An

John A DeNisco

Nicos Achilleoudis

DeFu Li

Elisheva Hochberg

Samir Vapiwala

Jean Philippe Vasseur

Jean-Phillippe Vasseur

In one embodiment, a Cable Modem Termination System (CMTS) generates a bandwidth grant message corresponding to a time segment. The CMTS identifies a portion of the time segment to be assigned according to received bandwidth request messages originating from downstream cable modems. The CMTS determines whether a remaining portion of the time segment can accommodate more than N broadcast contention slots, and if so, selects at least one of the cable modems for receiving an upstream bandwidth boost.

CMTS upstream channel bandwidth scheduler

In one example, a Cable Modem Termination System (CMTS) sends first bandwidth allocation messages to a first upstream transmit interface on a cable modem and send second bandwidth allocation messages to a second upstream transmit interface on the cable modem. The bandwidth allocation messages indicate transmit windows for the cable modem to range over the interfaces. The transmit windows included in the first bandwidth allocation messages are spaced based on receipt of ranging requests from the second upstream transmit interface, and the transmit windows included in the second bandwidth allocation messages are spaced based on receipt of ranging requests from the first upstream transmit interface.

Multi-channel ranging for a cable modem

Systems and methods for distinguishing a node failure from a link failure are provided. By strengthening the assumption of independent failures, bandwidth sharing among backup tunnels protecting links and nodes of a network is facilitated as well as distributed computation of backup tunnel placement. Thus a backup tunnel overlay network can provide guaranteed bandwidth in the event of a failure.

Distinguishing between link and node failure to facilitate fast reroute

In one embodiment, a method includes sending upstream to a nearest neighbor node, by a Client Label Switched Router (LSR), a downstream label map message of a Server-Forwarding Equivalence Class type (S-FEC-DOWN). In response to the S-FEC-DOWN, a downstream forwarding state from the nearest neighbor node to the Client LSR is established. An upstream label map message of a Client-Forwarding Equivalence Class type (C-FEC UP) is received from the nearest neighbor node. An upstream forwarding state corresponding to the C-FEC UP is then established by the Client LSR.

Half-duplex multicast distribution tree construction

In one embodiment, a first ranging timing description describing at least a duration of time during which a subject cable modem (CM) may burst and a duration of time during which the subject CM and other CMs in a multiple access network are not permitted to burst is translated into a second ranging timing description describing a duration during which a burst from the subject CM is expected to be received by a cable modem termination system (CMTS). The CMTS is conditioned to receive a burst from the subject CM during the duration of time described by the second ranging timing description. A timing offset is determined from at least an actual time a burst from the subject CM is received by the CMTS and the duration of time during which the subject CM and other CMs in the multiple access network are not permitted to burst to produce a determined timing offset. The determined timing offset is reported to compensate for delay in the multiple access network and the subject CM.

Modem timing offset compensation for line card redundancy failover

A method and apparatus for establishing multicast and unicast forwarding are disclosed. In one embodiment, a method includes transmitting path messages to a plurality of receivers, receiving a plurality of messages in response to the path messages and establishing unicast and multicast forwarding based on received unicast and multicast labels. Each of the receivers is associated with a sub-LSP (Label Switched Path) in a Point-to-Multipoint (P2MP) LSP and the response messages include a multicast label and at least one unicast label corresponding to a unicast path to one of the receivers.

Point-to-multipoint for multicast and unicast forwarding

A technique treats a protected forwarding adjacency (FA) as a dynamic entity in that it allows a backup tunnel associated with the FA to carry traffic for the FA, when it's primary tunnel has failed, up to a predetermined amount of time. If after the predetermined amount of time has elapsed and the FA has not recovered (e.g., the primary tunnel has not been reestablished), a network topology change is automatically triggered causing the network to converge on a new network topology. By triggering the network topology change, a path that is more optimal than the path associated with the backup tunnel may be subsequently determined to carry the traffic.

Dynamic forwarding adjacency

A technique triggers packing of path computation requests (PCRs) for traffic engineering (TE) label switched paths (LSPs) that are sent from one or more label-switched routers (LSRs) to a path computation element (PCE) of a computer network. According to the novel technique, incoming PCRs are packed into sets in response to a certain event, and one or more TE-LSPs (paths) are computed for each PCR of a particular set based on the PCRs of that set. Specifically, the PCE detects an event in the network ('network event') indicating that an increase in the number of incoming PCRs has occurred, or that an increase is likely to occur due to, e.g., a change in a network element. Once the network event has been detected, the PCE packs the incoming PCRs into configured-length sets, such as, e.g., for a specified time interval or a certain number of PCRs. The PCE computes paths for each PCR of a particular set while considering the other PCRs of that set, thereby reducing race conditions, signaling overhead, and set-up failures.

Trigger for packing path computation requests

A virtual overlay backup network is established to provide Fast Reroute capability with guaranteed bandwidth protection to a network that employs end-to-end circuits such as label switched paths (LSPs). In some implementations, backup bandwidth is allocated from an available backup bandwidth pool, as defined herein, available on each link. Complete bandwidth protection may be provided rapidly upon detection of a failure while available backup bandwidth is shared between independent failures. In one embodiment, this is accomplished by provisioning backup tunnels to protect all links and nodes, wherein total available backup bandwidth on any link is not exceeded by the requirements of backup tunnels protecting any single node but backup tunnels protecting different nodes may share bandwidth.

Implicit shared bandwidth protection for fast reroute

A Fast Reroute implementation where switchover time to backup tunnels upon failure of a protected network element is independent of a number of entries corresponding to forwarding equivalence classes forwarding over LSPs using that element. During normal operation of a packet forwarding device, adjacency information for a received packet is retrieved from a forwarding table based on a look-up of the packet's forwarding equivalence class. Upon failure of a link or node, the appropriate entries in this forwarding table are rewritten to implement the switchover to preconfigured backup tunnels. The switchover is effective even before the rewrite process has completed. Upon detection of the failure, forwarding processing shifts to a fix-up mode. During the fix-up mode, the look-up to the previously mentioned forwarding table is followed by a look-up to a backup tunnel adjacency table based on a pointer retrieved from the forwarding table. Operations relating to use of this backup tunnel adjacency table increase forwarding time somewhat but only during the special fix-up mode.

Enhanced switchover for MPLS fast reroute

Fast Reroute capability is added to an IP network to guarantee fast recovery to IP traffic in case of link or node failure without the need to deploy a full mesh of MPLS Traffic Engineering Label Switched Paths (LSPs). In one implementation, to protect a link, a 1-hop primary LSP is configured for the protected link and in addition a backup tunnel is configured to protect the 1-hop primary LSP. To protect a node, 2-hop primary LSPs are established for the link pairs traversing the node and backup tunnel(s) are configured to protect these 2-hop primary LSPs.

MPLS fast reroute without full mesh traffic engineering

A mechanism to alleviate bandwidth fragmentation in a network employing path computation element(s) to place MPLS Traffic Engineering tunnels. One application is a multiple Autonomous System or multiple area network employing distributed computation of MPLS Traffic Engineering LSPs. A particular path computation element may determine that bandwidth fragmentation is present based on monitoring of path computation failures where desired paths are blocked due to bandwidth constraints. In response to the detected bandwidth fragmentation condition, the path computation element floods a routing notification within its Autonomous System or area. Nodes respond to the routing notification by requesting reoptimization of their own previously requested Traffic Engineering LSPs allowing the path computation element an opportunity to alleviate bandwidth fragmentation.

Reoptimization triggering by path computation elements

Load balancing enables the use of linear programming techniques to reduce the complexity of computing backup tunnel placement for guaranteed bandwidth protection. The ability to load balance among multiple backup tunnels transforms the placement problem into one that may be characterized as a series of linear constraints usable as input to a linear programming procedure such as the simplex method. Each node may compute its own backup tunnels and signal the tunnels to its neighbors with zero bandwidth to allow implicit sharing of backup bandwidth.

Linear program-based technique for placing FRR TE tunnels with bandwidth guarantee

Load balancing among fast reroute backup tunnels in a label switched network is achieved. M backup tunnels may be used to protect N parallel paths. A single backup tunnel may protect multiple parallel paths, saving on utilization of network resources such as router state and signaling information. A single path may be protected by multiple backup tunnels, assuring that bandwidth guarantees are met under failure conditions even when no one backup tunnel with sufficient bandwidth may be found. A packing algorithm is used to associate individual label switched paths (LSPs) with individual backup tunnels. If an LSP cannot be assigned to a backup tunnel, it may be either rejected, or additional bandwidth is allocated to existing backup tunnels, or a new backup tunnel is established.

Load balancing for fast reroute backup tunnels

A method and apparatus for an improved Multiprotocol Label Switching (MPLS) system for traffic engineering is described. The improved MPLS system determines the actual traffic flow within a traffic engineering (TE) tunnel and dynamically adjusts the bandwidth to reflect the actual traffic flow. The actual traffic flow may be ascertained by accessing an average byte counter, which keeps track of the traffic flowing through the TE tunnel. Once the actual traffic flow is known the bandwidth is updated in accordance with the actual traffic flow. This allows the MPLS system to automatically maximize the bandwidth resources while minimizing operator intervention.

Growing community of inventors

Acton, MA, United States of America

Robert Goguen