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Network Aware Resource Broker (NARB)

Overview

Routing, path computation, and signalling on an inter-domain basis across topologies which include a heterogeneous mix of network technologies and vendor equipment is beyond what is defined in standards and also beyond the capability of current vendor equipment.

The NARB is an agent which represents a local Autonomous Domain (AD). The NARB serves as path computation engine from which end-systems or other devices can query to find out about availability of traffic engineered paths between specified source and destination pairs. The NARB is also responsible for inter-domain routing. NARBs peer across domains and exchange topology information to enable inter-domain path computation and Label Switched Path (LSP) provisioning. This inter-domain topology exchange can be based on the actual topology as discovered by listening to the local Open Shortest Path First (OSPF) protocol, or optionally based on an "abstracted" view of the domain topology (generated by configuration file or automatic synthesis of the OSPF link state database).

The specific NARB capabilities in this release include:

  • Intra-domain routing listener
  • Intra-domain path computation
  • Inter-domain routing
  • Domain level topology abstraction (in support of inter-domain routing)
  • Inter-domain path computation
  • Label Switched Path (LSP) management

To enable routing, path computation, and signaling in this environment the NARB provides several important functions. The NARB is an agent which represents a local Autonomous Domain (AD) and acts as a protocol listener to the intradomain routing protocols. In our implementation, the intradomain protocol is OSPF-TE. The NARB is also responsible for inter-domain routing. NARB’s peer across domains and exchange topology information to enable inter-domain path computation and Label Switched Path (LSP) provisioning.

The NARB’s utilize a modified version of OSPF-TE to share a link state database between domains. This inter-domain topology exchange can be based on the actual topology as discovered by listening to the local OSPF-TE protocol, or optionally based on an "abstracted" view of the domain topology (generated by configuration file or automatic synthesis of the OSPF-TE link state database). Domain abstraction provides mechanisms for an administrative domain to advertise to the outside world a highly simplified view of its topology. This allows domains to hide their real topologies as well as minimize the amount of external updates required. The trade-off is reduced accuracy for path computations. Each administrative domain can utilize configuration parameters to tailor its domain abstraction to the level desired.

One of the goals of our project is to evaluate various architectural issues. The domain abstraction features of NARB are geared toward allowing experimentation with differing levels of topology hiding. The resulting interdomain architecture would most accurately be described as a hybrid between the peer-to-peer and overlay models. The NARB currently holds the interdomain link state topology and does not advertise that data within its own domain. There are several reasons for this including the general inability for current GMPLS implementations to utilize such data as part of their CSPF calculations. Future configurations may leak some or all of this topology into local domain routing. The NARB also includes advanced algorithms which allow path computation with multiple constraints. These constraints include the standard GMPLS TE parameters as policy information to LSR’s so that appropriate action can be taken when processing provisioning messages. To accomplish this, the NARB translates the complex AAA and schedule information located in the 3D RCE into a simple policy directive which is distributed to the appropriate LSR’s.

Intradomain NARB functions

Interdomain NARB functions

Source Code

DRAGON's NARB code is incorporated into the DRAGON software releases. Please see the NARB page maintained by University of Southern California (USC) Information Sciences Institute (ISI) East to download the latest stable release.

Mailing Lists

Topic revision: r7 - 2006-11-27 - ChrisTracy
 
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