Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
  • H04L12/46—Interconnection of networks
  • H04L12/4604—LAN interconnection over a backbone network, e.g. Internet, Frame Relay
  • H04L12/4608—LAN interconnection over ATM networks
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q11/00—Selecting arrangements for multiplex systems
  • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
  • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
  • H04Q11/0478—Provisions for broadband connections
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L12/00—Data switching networks
  • H04L12/54—Store-and-forward switching systems 
  • H04L12/56—Packet switching systems
  • H04L12/5601—Transfer mode dependent, e.g. ATM
  • H04L2012/5629—Admission control
  • H04L2012/563—Signalling, e.g. protocols, reference model

Definitions

• the present invention relates to a communications network, and in particular to a network using a packet-based protocol such as Internet Protocol (IP).
• IP Internet Protocol
• IP Internet Protocol
• RSVP Resource reservation Protocol
• Switched Virtual Circuit may be used to "cut-through" from the terminal to the source, bypassing any intermediate routers, and providing a uniform and predictable QoS level.
• Standards for networks supporting such a capability have been proposed by the ATM (Asynchronous Transfer Mode) Forum and by the IETF (Internet Engineering Task Force). These standards are known as the Multi-Protocol over ATM (MPOA) and Multi-Protocol Label Switching (MPLS) standards.
• MPOA Multi-Protocol over ATM
• MPLS Multi-Protocol Label Switching
• a device in the network detects a data flow that is a candidate for an SVC cut-through, establishes the required SVC circuit, and initiates the diversion of the data through the cut-through.
• a method of operating a communications network comprising: a) establishing a data flow between a customer terminal and another data terminal, the data flowing conforming to a best-effort packet- routing protocol; b) subsequently initiating from the customer terminal the use of the a •switched virtual circuit through the network for the data flow.
• the present invention provides a method of using virtual circuits to give enhanced quality of service that differs significantly from previously proposed techniques. Whereas previously the use of virtual circuits has been regarded as purely an internal function within the network and has been hidden from the user, the present invention transfers control of the virtual circuit capability out of the network to the customer terminal.
• the user initially communicates with another data terminal, such as a server hosting a web site, using a best-effort protocol such as Internet Protocol. Only when and if the user subsequently elects to initiate the use of a switched virtual circuit does the network change the routing method for data flowing to or from the customer terminal.
• the method includes a step, prior to step (b), of communicating to the customer terminal data indicating potential availability of a switched virtual circuit in the network for the said data flow.
• This preferred feature of the invention facilitates the use of hybrid networks where only some data terminals may be connected to, e.g., ATM switches that support switched virtual circuits, while other data terminals may be connected only to, e.g., IP routers.
• Data is communicated to the customer to indicate when the use of a switched virtual circuit is possible.
• This data may be provided by a domain name server located in the network, or may be provided by the data server itself, for example in an HTML page indicating an ATM address and a bandwidth capability for the data server.
• the data is in the form of a URL (Uniform Resource Locator) that is specific to resources accessible via a circuit connected network, and the URL contains all the information necessary to set up the switched virtual circuit.
• URL Uniform Resource Locator
• the URL may be in the form: ⁇ circuit-connected identifier part > :// ⁇ service parameter part > * ⁇ address part > where * is a predetermined separator character.
• Figure 1 is a diagram showing a first example of a network embodying the invention
• FIGS. 2 to 5 show different phases in the process of establishing a switched virtual circuit (SVC);
• Figure 6 is a flow diagram
• Figure 7 is a state machine for a web browser used in implementing the invention.
• a customer terminal 1 in this example a personal computer, is connected to other data terminals 2,3 via a network 4.
• the data terminals 3,4 are web servers arranged to return HTTP (hypertext transport protocol) pages to the customer terminal 1 .
• the network 4 includes a first subdomain 4a that is part of the public Internet and includes a number of Internet Protocol (IP) routers 5. Suitable routers are commercially available devices such as CISCO series 7500 routers.
• IP Internet Protocol
• a second subdomain 4b comprises a number of ATM (asynchronous transfer mode) switches 6. Although, for ease of illustration, only two ATM switches are shown, in practice the subdomain 4b is likely to contain a larger number of switches.
• Suitable switches are commercially available devices such as ALCATEL 1 100 HSS Series 700 switches. These switches support ATM Switched Virtual Circuits (SVCs), in accordance with the ATM Forum V3.1 and V4.0 SVC definitions.
• SVCs ATM Switched Virtual Circuits
• the customer terminal includes an ATM card and is connected via an ATM access router 7 to both of the network subdomains.
• One of the data terminals 3,4 has only an IP interface and is connected to both of the subdomains 4a, 4b.
• the other of the data terminals 3,4 has an IP over ATM interface and is connected via that interface to both of the subdomains.
• the customer terminal 1 initially retrieves web pages from the data terminals 3,4 via the IP network 4a of the first subdomain.
• the web pages are displayed by a web browser application running on the customer terminal in a conventional fashion.
• the data flow between the customer terminal 1 and the data terminals 3,4 via the IP network is shown by the dashed broad line in the Figure.
• the data flow is effected by best-effort routing by the IP routers 5, and accordingly the quality of service varies depending on the loading of the routers.
• one of the data terminals 3,4 is also accessible via the ATM network of the second subdomain.
• the user wishes to retrieve data, such as a video data, that requires a high and guaranteed quality of service, from the said data terminal, then the user initiates a switched virtual circuit (SVC) via the subdomain 4b to the data terminal.
• SVC switched virtual circuit
• the subsequent data flow via this SVC is indicated by the solid broad line in Figure 1 .
• the customer terminal 1 is referenced “End User 1 "
• data terminal 3 is referenced “Content Provider 1”
• data terminal 4 is referenced “Content Provider 2”.
• Other customer terminals, referenced “End User 2” and “End User 3” are also shown.
• the connection from End User 1 to the IP subdomain 4a is via an Internet Service Provider (ISP) .
• ISP Internet Service Provider
• End user 1 is connected to the ISP via the ATM network 4b.
• the connection to the ISP gives End User 1 access to the Internet and to other data terminals having Internet connections. Some only of these other data terminals are also connected to the ATM network 4b.
• Content Provider 2 and End User 3 are connected to the ATM network 4b and can potentially be reached via an SVC cut-through, whereas Content Provider 1 and End User 2 have only have connections to the Internet End User 1 need to know which customers can be reached via an SVC cut-through. Examples of mechanisms by which the customer can know if it is possible to establish an SVC cut-through are : A) If a DNS (domain name server) translation of the chosen customer's URL to an ATM address exists.
• End User 1 could request a DNS translation for Content Provider 2, by communicating a URL "http://www.CP2.co.uk/" to the DNS.
• the Content Provider 2 URL would map to an ATM address.
• Both the IP address of Content Provider 2 and also the corresponding ATM address are returned to the End User 1 .
• the fact that an ATM address has been returned indicates to End User 1 that an SVC cut-through is possible.
• End User 1 may request a DNS translation for Content Provider 1 .
• the Content Provider 1 URL would not map to an ATM address, and this indicates to End User 1 that no SVC is possible in this case
• the originating customer identifies that an SVC cut-through is possible via information which could be downloaded in the form of HTML, that is as a web page displayed by the web browser application. This information would need to include the ATM address, and may also include Bandwidth availability, QoS information and an indication of cost.
• a content provider may have an ATM specific URL in the format "atm:// ATM parameters @Server ATM address. sub-address/full-path-of-file.” This mechanism may be combined with (B), that is, the ATM specific URL may be displayed on an HTTP page, either on the server to which the ATM specific URL relates, for example Content Provider 2, or on another server that such as Content Provider 1 , that is not itself on the ATM network but includes links to resources that are on the ATM network.
• Figure 4 shows the SVC established in the ATM network. Once this is established, the End User 1 can view the selected application or data on Content Provider 2. When End User 1 has finished viewing material that requires an SVC, then the cut-through is released using signalling between the customers across the ATM network, again using standard ATM-F and ITU-T signalling protocols. This release phase is shown in Figure 5.
• mechanism (C) that is the use of ATM-specific URL's.
• the Web browser application running on the customer terminal is adapted to support Winsock (Windows Sockets) version 2 functionality (Windows is a trademark of Microsoft Corporation) .
• Figure 6 is a flow diagram illustrating in further detail the behaviour of a system operating using ATM URL's
• Figure 7 is a state machine diagram for the web. browser. The steps shown are as follows:
• the user searches web pages for the relevant information, as if using a standard web browser. No ATM SVC has been established. 2.
• the web browser performs the following operations:- 3.
• First the Web browser has to determine that this is an ATM URL request, if so, it has to parse/decode the ATM information. This information is stored and used to help construct the profile of the signalling message capability, and determines the socket and protocol state machine type.
• the ATM URL does not contain all the ATM lE's (Information Elements) defined in the signalling protocols. This is for two reasons. Firstly, not all the defined lE's are sent in the ATM signalling SETUP or LEAF SETUP REQUEST messages. Secondly, the ATM information within the URL contains only the information required by the web browser.
• the API is free to add valid additional ATM information before initiating the ATM SVC.
• additional ATM information could be the Calling Party Number, Calling Party Sub-address, Transit Network Selector (TNS) Broadband Sending Complete, Broadband Repeat Indicator, Broadband High and Low Layer Information, Narrowband High and Low Layer Compatibility etc.
• TMS Transit Network Selector
• the web browser Before data can be sent between the two entities, the web browser has to use the correct protocol state machine implementation for the URL scheme.
• the ATM protocol state machine has to be also associated with the ATM socket descriptor. As the URL scheme is 'atm://' the web browser knows it should use the ATM protocol state machine and create ATM sockets.
• the state machine is used by the web browser to define its behaviour when sending and receiving data over a connection. This state machine has been developed for use with ATM connections.
• the ATM state machine is described in further detail below with reference to Figure 7. . If the web browser client determines after decoding the ATM URL that no ATM parameter value(s) need to be specified manually by the'Web browser, then the ATM GUI is not launched and the Web browser uses the underlying WinSock2 Application Programming Interface (API) functionality to establish an ATM SVC to the desired destination. The characteristics of this ATM SVC will be the same as those values returned from the HTTP server in the ATM URL. This corresponds to state ATM_GET_SETTINGS in Figure 4.
• API Application Programming Interface
• ATM GUI Graphic User Interface
• This ATM GUI is an extension to traditional web browser applications, in that it allows the end users to enter values for the ATM parameters coded as 'User Defined' within the ATM URL.
• the values entered by the end user via the ATM GUI are also stored to help build the profile or characteristics of the signalling messages, which will be sent to the ATM server(s). This corresponds to state ATM_GET SETTINGS in Figure 4.
• WinSock2 is responsible for creating ATM sockets for communication between the web browser and ATM server. This involves the web browser and ATM server invoking a number of WinSock2 function calls. When the ATM sockets have been created but not connected together, then this corresponds to state ATM_BEGIN_CONNECT, as shown in Figure 7.
• WinSock2 communicates with the underlying signalling protocol stack to establish an ATM SVC and logically connects the two ATM sockets together.
• the WinSock2 SPI is responsible for taking the ATM URL parameters, together with any information added by the user, and coding them into the correct format to be used with the underlying signalling protocol, which may be, e.g., UNIv3.0, UNIv3.1 , UNIv4.0, UNIv4.1 or Q.2931 .
• the WinSock2 SPI is also responsible for including mandatory Signalling lE's, not defined in the ATM URL.
• Examples of these mandatory lE's include, the Protocol Discriminator, Call Reference, Message Length, Message Type and Endpoint Reference (for Point-to-Multipoint connections) plus LU Sequence Number (for LU connections) . If the ATM SVC is successfully established then, charging records for that connection can be generated and state ATM SEND_REQUEST is entered, see Figure 7. If however, the SVC fails to be established, the web browser launches a window to inform the user of the event and enters the ATM_ERROR_FOUND state.
• the number of bytes of data received by the web browser is incremented and compared with the file size obtained at the GET_FILE_SIZE state, of Figure 7.
• ATM_TRANSFER_STOP state is entered, else the transfer continues.
• control is passed back from the state machine to the calling application, so it won't block user commands.
• Knowing the size of the file allows the web browser to display the transfer progress status (indicating the proportion of bytes received compared to the total number yet to be received) and to estimate the remaining time of the transfer.
• the web browser has to know how to interpret each type of data.
• MIME Modular Extensions
• the state machine enters the ATM_ERROR_DONE state. This may occur for several reasons, for example when the ATM server did not send the size of the file in the first packet; or when the transfer of a buffer cannot be completed because either there was a network or application failure etc.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Data Exchanges In Wide-Area Networks (AREA)

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• 2000
  • 2000-03-08 CA CA002367399A patent/CA2367399A1/en not_active Abandoned
  • 2000-03-08 AU AU29311/00A patent/AU779785B2/en not_active Ceased
  • 2000-03-08 WO PCT/GB2000/000846 patent/WO2000056031A1/en not_active Application Discontinuation
  • 2000-03-08 JP JP2000605362A patent/JP2002539717A/ja active Pending
  • 2000-03-08 EP EP00907847A patent/EP1159808A1/de not_active Withdrawn

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