Hierarchy tree-based quality of service classification for...

Details Hierarchy tree-based quality of service classification for... Hierarchy tree-based quality of service classification for...

2002-10-28

2004-09-21

Jung, Min (Department: 2663)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S417000

Reexamination Certificate

active

06795441

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to the field of communications. More specifically, the invention relates to hierarchy tree-based quality of service classification for packet processing.
BACKGROUND OF THE INVENTION
Maintaining efficient flow of information over data communication networks is becoming increasingly important in today's economy. Communications networks are evolving toward a connectionless model from a model whereby the networks provide end-to-end connections between specific points. In a network which establishes specific end-to-end connections to service the needs of individual applications, the individual connections can be tailored to provide a desired bandwidth for communications between the end points of the connections. This is not possible in a connectionless network. The connectionless model is desirable because such a model saves the overhead implicit in setting up connections between pairs of endpoints and also provides opportunities for making more efficient use of the network infrastructure through statistical gains. Many networks today provide connectionless routing of data packets, such as Internet Protocol (“IP”) data packets, over a network which includes end-to-end connections for carrying data packets between certain parts of the network. The end-to-end connections may be provided by technologies such as Asynchronous Transfer Mode (“ATM”), Time Division Multiplexing (“TDM”) and Sychronous Optical Network (SONET) and Synchronous Digital Hierarchy (SDH).
A Wide Area Network (“WAN”) is an example of a network used to provide interconnections capable of carrying many different types of data between geographically separated nodes. For example, the same WAN may be used to transmit video images, voice conversations, e-mail messages, data to and from database servers, and so on. Some of these services place different requirements on the WAN.
A typical WAN comprises a shared network which is connected by access links to two or more geographically separated customer premises. Each of the customer premises may include one or more devices connected to the network. More typically, each customer premise has a number of computers connected to a local area network (“LAN”). The LAN is connected to the WAN access link at a service point. The service point is generally at a “demarcation” unit or “interface device” which collects data packets from the LAN which are destined for transmission over the WAN and sends those packets across the access link. The demarcation unit also receives data packets coming from the WAN across the access link and forwards those data packets to destinations on the LAN. One. type of demarcation unit may be termed an ESP (Enterprise Service Point).
A network service is dependent on the amount of data it can send and receive from a source device to one or more destination devices. Therefore, the quality of a network service is dependent on the amount of network resources (such as uptime, outages, bandwidth, delay, loss, and jitter) the network can utilize to transfer its data. However, in a conventional IP network, all network services share all the network resources on a first come, first serve (“best effort”) basis. This may be detrimental to some network services since some services require more network resources than other services.
For example, a typical video conferencing service requires much more data to be sent than a typical e-mail service. Transmitting a video signal for a videoconference requires fairly large bandwidth, short delay (or “latency”), small jitter, and reasonably small data loss ratio. An e-mail service requires far less network resources than a video conferencing service because the e-mail service often has relatively little data to send to its destinations and it is generally acceptable if an e-mail transmission is slightly delayed in transiting a network. Transmitting e-mail messages or application data can generally be done with lower bandwidth but can tolerate no data loss. Furthermore, it is not usually critical that e-mail be delivered instantly, so e-mail services can usually tolerate longer latencies and lower bandwidth than other services. In addition, the e-mail service requires only enough network resources to send data in a single direction. Conversely, the typical video conferencing service requires enough network resources to send data constantly and seamlessly in two directions. This may be required if all participants in the video conference want to see each other, and thus requires an individual's image to be sent to the other participants and the other participant's images to be received.
If the network resources are shared in a best effort fashion between these and other types of network services, the e-mail service will deliver e-mail extremely fast, but the video conferencing service would not be able to display a very clear picture. What is desired is to have a policy.where the network resources utilization is weighted such that the video conferencing service receives more network resources than e-mail services.
Typically, an enterprise which wishes to link its operations by a WAN obtains an unallocated pool of bandwidth for use in carrying data over the WAN. While it is possible to vary the amount of bandwidth available in the pool (by purchasing more bandwidth on an as-needed basis), there is no control over how much of the available bandwidth is taken by each application.
Again, guaranteeing the Quality of Service (“QoS”) needed by applications which require low latency is typically done by dedicating end-to-end connection-oriented links to each application. This tends to result in an inefficient allocation of bandwidth. Network resources which are committed to a specific link are not readily shared, even if there are times when the link is not using all of the resources which have been allocated to it. Thus committing resources to specific end-to-end links reduces or eliminates the ability to achieve statistical gains. Statistical gains arise from the fact that it is very unlikely that every application on a network will be generating a maximum amount of network traffic at the same time.
If applications are not provided with dedicated end-to-end connections but share bandwidth, then each application can, in theory, share equally in the available bandwidth. In practice, however, the amount of bandwidth available to each application depends on things such as router configuration, the location(s) where data for each application enters the network, the speeds at which the application can generate the data that it wishes to transmit on the network and so on. The result is that bandwidth may be allocated in a manner that bears no relationship to the requirements of individual applications or to the relative importance of the applications. There are similar inequities in the latencies in the delivery of data packets over the network.
The term “Quality of Service” is used in various different ways. In general, QoS refers to a set of parameters which describe the required traffic characteristics of a data connection. The term “QoS” generally refers to a set of one or more of the following interrelated parameters which describe the way that a data connection treats data packets generated by an application: a minimum bandwidth, a maximum delay, a maximum loss and jitter. A minimum bandwidth is a minimum rate at which a data connection should be capable of forwarding data originating from the application. The data connection might be incapable of forwarding data at a rate faster than the minimum bandwidth but should be capable of forwarding data at a rate equal to the rate specified by the minimum bandwidth. The maximum delay is a maximum time taken for data from an application to completely traverse the data connection. QoS requirements are met only if data packets traverse the data connection in a time equal to or shorter than the maximum delay. The maximum loss is a maximum fraction of data packets from the application which may not be successfully transmitted across t

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