Load balancing among media gateways

Details Load balancing among media gateways Load balancing among media gateways

1999-12-15

2004-03-23

Ho, Duc (Department: 2665)

Multiplex communications

Pathfinding or routing

Combined circuit switching and packet switching

C370S401000, C370S465000, C379S219000, C379S088170, C709S249000

Reexamination Certificate

active

06711159

ABSTRACT:

FIELD OF INVENTION
This invention relates to Internet telephony and its inter-working with the legacy Public Switched Telephone Network (“PSTN”). More specifically, it relates to a system and method for balancing the load among Internet Telephony Gateways connected to the PSTN.
BACKGROUND OF THE INVENTION
Internet telephony encompasses a number of technologies for the transport of voice traffic over Internet Protocol (“IP”) networks. At a very high level, IP telephony can be divided into a media portion or plane, and a signaling and call control portion or plane. The media plane provides functionality required for media transport, such as packetization of voice data, packet delivery, and media playout at the destination. The signaling plane provides functionality required to set up, tear down, and manage calls.
An important aspect of Internet Telephony is the inter-working of the IP network with the existing PSTN. In the context of PSTN inter-working, the media and signaling planes include expanded functionality in order to connect different types of networks. Thus, the media plane incorporates components that translate and map the voice data between the circuit-switched PSTN and the packet-switched IP network, enabling it to act as a gateway between the two different kinds of media transport. Similarly, the signaling and call control plane incorporates components that translate and map signaling and call control protocols between the PSTN and the IP networks, in order to set up, tear down, and manage calls which traverse both types of networks.
The development of common protocols and architectures for the PSTN inter-working function is a major focus of several standards groups, including the Internet Engineering Task Force (“IETF”) and the International Telecommunications Union (“ITU”). While this is a large task, requiring the resolution of many technical issues, a general architecture has emerged in which the media plane and signaling and call control plane are viewed as distinct elements. The media plane component is commonly referred to as an Internet Telephony Gateway (“ITG”), or more generally as a Media Gateway (“MG”). The signaling and call control plane component is further divided into two elements. One element both controls the MG remotely, and handles IP-side signaling and call control with peer elements on the IP network. This element is called the Media Gateway Controller (“MGC”). The other element provides the mapping and translation between the PSTN and IP signaling and call control protocols. This element is called the Signaling Gateway (“SG”). The MGC and MG are usually configured in a master (MGC) and slave (MG) relationship, and multiple MGs may be under the control of a single MGC. Additionally, the MGC and MG may be combined in the same device, or alternatively, separate devices remote from each other.
For a call that traverses an IP network and terminates on the PSTN, the ITG that provides the gateway function to complete the call is commonly termed the egress gateway. For any given call with an IP-to-PSTN leg, it may be the case that more than one egress gateway is available. This could occur if the protocol used to set up the call has identified multiple, candidate egress gateways, each with appropriate network connectivity to the desired (egress) Local Exchange Carrier (“LEC”). For example, if multiple ITGs are clustered under MGs in a hierarchical fashion, so as to appear to the system as large virtual ITGs, the identification of several alternative egress gateways will be a common occurrence. Under such circumstances, it will generally be very desirable to have a method to achieve a balance of handled calls among the egress gateways in order to optimize usage of the collective ITG resources. This is important for overall system performance, as well as to avoid subjecting a disproportionately large number of calls to possible interruption in the event of ITG failure. It will also generally be very desirable under such circumstances to provide load balancing that is distributed, rather than controlled and maintained by a central MGC or ITG, to help prevent traffic bottle necks.
Accordingly, it is desirable to provide a system and method for achieving load balancing among egress MGs, such as ITGs, without resorting to centralized control or the attendant need for centralized port management and state maintenance. By balancing the load among egress MGs, calls can be distributed roughly uniformly among available egress MGs to preserve MG resources and optimize overall system performance. In addition, by distributing the load balancing without resorting to centralized control and maintenance, potential traffic bottle necks at a central controller can be avoided.
SUMMARY OF THE INVENTION
The present invention provides a method for load balancing among gateway devices comprising the steps of: obtaining a list of a plurality of gateway devices, and sending a request to a first gateway device on the list. The method also comprises the steps of determining whether the first gateway device has an available port, removing the first gateway device from the list if the first gateway device does not have an available port, and sending the request to a second gateway device on the list if the first gateway device does not have an available port. The method further comprises the steps of determining whether the request should be accepted by the first gateway device if the first gateway device has an available port, selecting the available port of the first gateway device if the request is accepted, and sending the request to a second gateway device on the list if the request is not accepted by the first gateway device.
The present invention also provides a method for load balancing among gateway devices used to complete calls between a first network and a second network. The method comprises the steps of obtaining a list of a plurality of gateway devices that are candidates for completing a call between the first and second networks, and sending a request to a first gateway device on the list, with the request including the list. The method further comprises the steps of determining whether the first gateway device has an available port to complete the call, removing the first gateway device from the list if the first gateway device does not have an available port, and sending the request to a second gateway device on the list if the first gateway device does not have an available port. In addition, the method comprises the steps of determining whether the request should be accepted by the first gateway device if the first gateway device has an available port, selecting the available port of the first gateway device if the request is accepted, and completing the call using the available port of the first gateway device if the request is accepted. The method also comprises the steps of assigning a cost value for completing the call to the first gateway device if the request is not accepted by the first gateway device, and sending the request to a second gateway device on the list if the request is not accepted by the first gateway device.
Moreover, the present invention provides a system for balancing the load among gateway devices comprising a list of a plurality of gateway devices that are candidates for completing a call between a first and a second network. The system also comprises a first gateway device positioned first on the list and in communication with the first and second networks, and a second gateway device positioned second on the list and in communication with the first and second networks. Both the first and second gateway devices also each have at least one port. The system further comprises a request including the list, with the request capable of being sent to the first and second gateway devices. In addition, the system comprises a first decision algorithm to determine whether the first gateway device has an available port to complete the call, and a second decision algorithm to determine whether the request should be accepted by the first gatew

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