Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-03-11
2003-07-15
Kizou, Hassan (Department: 2662)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S230000, C370S235000
Reexamination Certificate
active
06594268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to packet networks, and, more particularly, to adaptive routing of packets in a communications network based on quality of service provisioning.
2. Description of the Related Art
Packet network service providers, such as those providing Internet Protocol (IP) networks, are presently developing and providing differentiated services. In particular, service providers are interested in differentiated services as part of provisioning and maintaining networks for customers with a variety of voice and data needs. For example, virtual private networks (VPNs) allow service providers to establish and tear-down connections for a large number of users, while billing only one customer or client (e.g., a large corporation or government agency) for the service. However, the customer or client may require a certain amount of guaranteed bandwidth, minimum transport delay, or other metric for some or all of the data transported through the VPN. Service providers generally desire a higher revenue for data transported through the VPN when a customer demands such differentiated services.
In the art, the term “physical path” denotes the path between source and destination pairs for a given communication stream of data, or packet flow, together with intermediate nodes, if any, and the physical links that connect the nodes. In networks of practical size and complexity, many sets of multiple physical paths may exist, each provisioned to carry one or more corresponding packet flows. The network operator may specify a predetermined bandwidth for the corresponding stream or packet flow along each link of the possible physical paths. The specified bandwidth may equal the full bandwidth, or some quantity less than the full bandwidth, or no bandwidth at all. Although a physical path may exist between a source and destination pair, the full bandwidth of the physical path links may be unavailable for the corresponding packet flow.
In addition, the term “logical path” (also called a “virtual path”) denotes a path between a given source and destination pair as defined by connection metrics, such as delay or bandwidth. Logical (virtual) paths are not determined purely by physical considerations, but instead are partly defined by parameters that may be specified and/or changed. Individual virtual paths may require less than the fully assigned bandwidth physically available on the physical links that the paths occupy. Thus, several virtual paths may co-exist along part or all of a physical path, allowing each physical link of the network to simultaneously support several virtual paths.
Packet networks that provide differentiated services generally include a routing method that allows the network to determine a logical path through the network from a given source to a given destination. The routing method may be part of a process performed in each router of the network. Each router may learn the network topology by exchanging link and router information between directly connected routers. Once the router determines the network topology, the router may employ a path-selection process that determines the logical path through a network between the source and destination pair over the physical links according to-predefined connection metrics. Each router determines the same logical path through the packet network given the same information. Packets received by each router are then routed along the determined path.
A standard protocol employed by IP networks to determine network topology and link routing is the Open Shortest Path First (OSPF) protocol, as outlined in J. Moy, “OSPF Version 2,” Internet Draft, Request for Comment (RFC) 2178, July 1997. The OSPF protocol employs the destination (i.e., shortest path to destination) as the metric for the path-selection process. However, with destination as the only metric, only a “best effort” is employed to route packet flows. Best effort implies that, while the packets are re-routed, no other QoS provisioning commitment, such as minimum bandwidth, delay or loss, applies to the packet flow. Routers of the prior art may route packets based on other factors, such as available bandwidth. However, when the OSPF protocol is employed as the routing method, distribution of packet flows over the links is based on shortest path and not provisioned QoS commitments.
Routing methods may determine logical paths and allocate corresponding bandwidth to the links in the network, with such allocation according to the source and destination pair, subnetwork, and class of service. This path-selection method or determination may be referred to as logical network design. One important element of logical network design is selection of a set of physical paths through the network having sufficient capacity for carrying the estimated traffic of a communication stream or packet flow. The routing method may base the determination on such factors as the network topology, the currently available buffer space at the nodes, and the currently available link capacities.
Significantly, the network operator may have QoS commitments with its customers, such as guaranteed bandwidth or maximum cell-loss probability. The path-selection process may account for such commitments, but the routing method may require simplifications to characterize variable traffic characteristics in a form that the routing method can use for logical path determination. For example, certain networks, particularly high-speed networks, may support the networking protocol known as asynchronous transfer mode (ATM). Such high-speed networks typically carry multiple services having different traffic characteristics, including both constant bit rate traffic and variable bit rate traffic. An important simplification for routing methods considering variable bit rate traffic in networks, such as ATM networks, is provided by the concept of “effective bandwidth.”
Effective bandwidth of a packet flow defines the bandwidth of the packet flow in terms of the node buffer size and the average and peak rates of the packet flow, assuming the node operates with a leaky bucket regulator. An effective bandwidth may be determined for each packet flow, of a network where the packet flows are multiplexable, the total effective bandwidth of all packet flows is less than or equal to the total network capacity, and the packet flows exhibit loss-less performance. (i.e., the packet flows may be rearranged over multiple physical paths while maintaining desired delay or bandwidth for each packet flow). For networks having both multiplexable and non-muliplexable packet flows, the two types of traffic may be separately analyzed, with portions of the total network capacity allocated to each traffic type.
Effective bandwidth, and allocation of bandwidth and buffer capacity based on effective bandwidth, is described in detail in A. Elwalid et al., “A New Approach For Allocating Buffers and Bandwidth to Heterogeneous, Regulated Traffic in an ATM Node,”
IEEE Journal on Selected Areas in Communications
, Vol. 13, No. 6, (August 1995) 1115-1127 (incorporated herein by reference and referred to as “Elwalid et al.”). A routing algorithm that accounts for variable bit rate traffic in ATM networks with effective bandwidth, is described in detail in U.S. Pat. No. 5,838,663, issued on Nov. 11, 1998 entitled “A Method for Admission Control and Routing by Allocating Network Resources in Network Nodes”, which is incorporated herein by reference.
Once logical paths are specified, the routers of the network generally must support at least two types of messages for the packet flows and network administration: data messages and control messages. Data messages are packets containing user information transported between the source and destination pair. Control messages are messages interpreted by network elements, such as the routers, to administer connections and exchange network information. These control messages may be employed to ensure that the packets are interpreted and routed in a manner that pro
Aukia Petri
Lakshman T. V.
Mitra Debasis
Ramakrishnan Kajamalai G.
Stiliadis Dimitrios
Kizou Hassan
Lucent Technologies - Inc.
Mendelsohn and Associates PC
Tsejaye Saba
LandOfFree
Adaptive routing system and method for QOS packet networks does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adaptive routing system and method for QOS packet networks, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adaptive routing system and method for QOS packet networks will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3107566