EP1356635A1

EP1356635A1 - Method and server for accessing a digital network

Info

Publication number: EP1356635A1
Application number: EP02700387A
Authority: EP
Inventors: Gwenael Le Lay; Jean-François LAMARD; Marc Le Ligne
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2001-01-31
Filing date: 2002-01-23
Publication date: 2003-10-29
Also published as: WO2002062015A1

Abstract

The invention enables to set up a connection through a packet mode network (5) between a user terminal (11) and service provider server (2), in accordance with a connection mode selected among a plurality of different connection modes run by the digital network (5). The invention is characterised in that it consists in: identifying said specific connection mode, from data transmitted by the user terminal (1); selecting, on the basis of said specific connection mode, at least a server for accessing the services among a plurality of access servers to the services (61, 62), such that the selected service access server is compatible with said specific connection mode; transmitting at least an accounting message of the connection to said at least one selected service access server.

Description

METHOD AND SERVER FOR ACCESSING A DIGITAL NETWORK

The present invention relates to a method and a server for accessing a digital network, in particular a packet mode transport network, as well as a system incorporating such a server. It relates to the field of digital networks, and in particular packet mode transport networks, for example supporting a protocol such as TCP / IP (Transmission Control Protocol / Internet Protocol).

A network access server is an equipment which has the function of interconnecting an access network to the transport network. The function of the access network is to collect data flows from user terminals which are connected to the access network. Servers from different service providers or ISPs (from the English “Internet Service Provider”) are connected to the transport network. When a user wishes to access a service from an ISP, it is necessary to establish a connection between the user's terminal and the ISP server.

Depending on the type of service concerned and / or according to the ISP, such connections can be established according to different respective connection modes. With regard to IP networks (from the English “Internet Protocol”), such connection modes are in particular the SLIP mode (from the English “Sériai Llne Protocol”), the PPP mode (from the English “Point -to-Point Protocol "), te L2TP mode (from English" Level 2 Tunneling Protocol ") or even TCP-raw mode (" Transmission Control Protocol-Raw "). The network access server is said to be shared when it allows access to services requiring the establishment of connections according to different connection modes. These connection modes are associated with one or more respective services. A shared access server therefore accepts connections according to several different connection modes, associated with one or more respective services.

For access to certain services, authentication messages are exchanged between the user's terminal, the network access server, the ISP server, and / or a particular server called the access server. services, which is connected to the transport network. The purpose of these messages is to identify the user and to verify that he is authorized to access the service (for example because he has paid for a subscription for this purpose). In general, accounting messages are also exchanged between the user's terminal and / or the network access server on the one hand, and the service access server on the other. 'somewhere else. These messages are notably exchanged when establishing the connection (so-called "accounting start" messages in English) and when releasing the connection (so-called "accounting stop" messages in English), for statistical purposes and / or pricing.

However, a problem results from the fact that certain equipment currently installed as a service access server is incompatible with certain determined connection modes. For example, the service access server which is connected to the IP network core of the French operator FRANCE TELECOM, which was designed and produced by the manufacturer ALCATEL, is incompatible with the above-mentioned TCP-Raw connection mode. In fact, in this connection mode, counting messages are transmitted to the service access server without being preceded by authentication messages. These counting messages are therefore not recognized by the service access server, which reacts by generating inter-node synchronization messages. This produces an overload of the internal access server traffic, which can lead to its saturation. In order to avoid this drawback, it would be possible to intervene at this server, to annihilate the overload of internal traffic. However, this would only remove the effects, not the cause of the problem.

We could also consider modifying the profile of the network access server (shared server), so that it simulates a connection mode compatible with the service access server. In the example, this would amount to artificially sending authentication messages to the service access server, prior to the transmission of the counting messages. This proves however difficult to implement, to alleviate all the possible causes of incompatibility between a considered connection mode and the service access server.

The invention proposes a solution to the above problem, which is based on a completely different approach. The invention is applicable when a network access server is shared, that is to say that it supports several modes of connection determined for the connection of a user terminal to the server of any ISP via the transport network, each of these connection modes being associated with one or more respective services, and that a plurality of access servers services are linked to the transport network, each connection mode corresponding to at least one service access server which is compatible with it. In essence, the invention consists in directing counting messages for a determined connection, as a function of the connection mode of the connection, to at least one service access server which is compatible with the connection mode. In this way, connection count messages are only transmitted to a service access server which is compatible with the corresponding connection mode. Where appropriate, connection authentication messages are also transmitted to this service access server, prior to the transmission of the counting messages for said connection. More particularly, the invention provides a method of accessing a network in packet mode for establishing a connection across the network between a user terminal and a server of a service provider, according to a mode of connection determined from a plurality of different connection modes supported by the network, comprising the steps consisting in:

- identify said determined connection mode, from data transmitted by the user terminal;

- Select, according to said determined connection mode, at least one service access server from a plurality of service access servers, so that the selected service access server is compatible with said connection mode determined;

- transmit at least one counting message associated with the connection to said selected service access server.

The invention also provides a packet mode network access server for establishing a connection between a user terminal and a server of a service provider across the network, according to a determined connection mode. among a plurality of different connection modes supported by the network, characterized in that it comprises: - Means for identifying said determined connection mode, from data transmitted by the user terminal;

means for selecting, as a function of said determined connection mode, at least one service access server from a plurality of service access servers, so that the selected service access server is compatible with said service determined connection mode;

- Means for transmitting at least one counting message associated with the connection to said at least one selected service access server. Finally, the invention proposes a system comprising a packet mode network, at least one user terminal, at least one server of a service provider, the system further comprising a plurality of servers for accessing services compatible with at least one respective connection mode, as well as at least one network access server as defined above, for establishing a connection between the user terminal and the server of the service provider through the network.

According to additional characteristics, taken individually or in combination:

the user terminal is connected to an access network which is interconnected to the network in packet mode by the network access server;

- The packet mode network is an IP network (from the English “Internet Protocol”);

- the packet network is a backbone network;

- the service access servers are RADIUS servers (from the English “Remote Authentication Dial-ln-User Service”), that is to say that they operate according to the RADIUS protocol (see RFC 2138).

Other characteristics and advantages of the invention will become apparent on reading the description which follows. This is purely illustrative and should be read with reference to the accompanying drawings in which there is shown: - in Figure 1: the schematic architecture of a system according to the invention;

- in Figure 2: a diagram of a network access server according to the invention; - in Figure 3: a flowchart showing steps of a method according to the invention;

- in Figure 4: a diagram showing an example of application of the invention. In Figure 1, there is shown schematically the architecture of a system according to the invention.

The reference 5 designates a digital network, in particular a packet mode transport network. This is for example an IP network. At least one server 2 of an ISP is connected to the network 5. The reference 4 designates an access network or subscriber collection network, which can use various technologies for the collection of these subscribers. It can be, for example, a switched telephone network, a radiocommunication network such as GSM or UMTS. It can also be a local area network or LAN (from the English “Local Area Network”), an ADSL network, or others. User terminals such as 11 to 13 are connected (physically and / or logically) to the access network 4.

The system further comprises a plurality of service access servers such as 61 and 62, which are connected to the network 5. They are sometimes called "Service Access Platform" or PAS. These servers fulfill various functions related to the management of access to services accessible via the network 5. These functions are commonly designated by the acronym AAA (from the English “Authentication Authorization Accounting”). In particular, when a connection must be established between a user's terminal and the server of an ISP, authentication messages can be transmitted to a service access server, with a view to identifying the user and the verification of his authorization to access the services offered by the ISP. These messages contain, for example, a "login", that is to say the combination of a user name and a password. Likewise, counting messages are generally transmitted to it when the connection is established and released, in order to keep up to date information used for billing users or for statistical reasons. These messages refer for example to the duration of the connection, the volume of data sent and / or received by the user terminal, etc. Finally, the system includes a network access server 31, which interconnects the access network 4 and the transport network 5. The function of the server 31 is to concentrate the information flows collected by the access network

4 to the first node of the transport network 5. In addition, it also has the function of transmitting authentication messages and / or counting messages to a service access server. When the access network is a narrowband network (typically up to 128 Kb / s), the network access server is commonly called NAS (from the English “Network Access

Server ”). In the case where it is on the contrary a broadband network (typically of the order of 500 Kb / s), the network access server is

-commonly called BAS (from English “Broadband Access Server”).

According to the invention, the server 31 is a shared server, that is to say that it supports connections according to different determined connection modes. Connections are established to allow the user terminals 11 to 13 to connect to a server of an ISP such as the server 2, to access a service. Each connection mode is associated with one or more respective services. It is therefore according to the type of service required, and / or the properties of the server of the ISP concerned, that the connection connection mode is chosen, when establishing the connection, among said connection modes determined.

In addition, there is, for each connection mode supported by the network 5 and by the network access server 31, at least one service access server which is compatible with this connection mode, and which is connected to the network 5. In other words, each connection mode corresponds to at least one access server to the system services which is compatible with it.

In the diagram of Figure 2, there is shown an access server according to the invention. In this figure, the same elements as in Figure 1 have the same references.

The network access server 31 interconnects the access network 4 and the transport network 5. For this purpose, it is connected to the first router 51 of the latter.

The network access server 31 includes means for implementing the method according to the invention. In an exemplary embodiment, these means are software means, and are part of the profile of the server. This profile is stored in a memory 313 and executed in a control unit 311 of the server 31.

The server 31 further comprises a database 312 which contains data determining connection modes, in correspondence with information which can be transmitted by the user terminal and which are specific to these respective connection modes.

The timing diagram of FIG. 3 shows the steps of the method according to the invention.

The method allows access to the transport network 5, for establishing a connection through this network between for example the user terminal 11 and the server 2 of an ISP, according to a connection mode determined from among plurality of different connection modes supported by the network. It will be recalled that, in practice, each connection mode is associated with one or more respective services to which the user can have access by connecting to the server of an ISP, such as server 2.

The method firstly comprises a step 21 consisting in identifying the connection mode of the connection, from data transmitted by the user terminal. This data may include a call number associated with the server 2. It will in particular be a telephone call number when the access network is a telephone network. In addition or alternatively, this data may include a "login" consisting of a user name and a password.

These data are compared with data of the same kind, stored in the database 312 of the network access server 31 (FIG. 2), with which are respectively associated data determining the corresponding connection mode. Thus, reading from this database makes it possible to identify the connection mode of the connection from the data transmitted by the user terminal.

The method further comprises a step 22 consisting in selecting, as a function of the connection mode identified in step 21, at least one service access server from a plurality of service access servers 61, 62 which are connected to the network 5. The service access server which is thus selected is compatible with the connection mode of the connection. Said otherwise, the criterion taken into account for this selection is the compatibility of the service access server (s) with the connection mode of the connection.

Finally, the method comprises a step 24 consisting in transmitting at least one counting message associated with the connection, to said at least one service access server which was selected in step 22. In particular, such a message, called "Accounting start" in English is transmitted when establishing the connection, and another such message, called "accounting stop" in English, is transmitted when the connection is released. Depending on the connection mode concerned, these messages are generated either by the user terminal 11 or by the network access server 31.

For certain connection modes, in particular for PPP and

L2TP presented in the introduction, the method can also include, between step 22 and step 24 above, a step 23 consisting in transmitting authentication messages associated with the connection, to said at least one service access server which was selected in step 22.

In Figure 4, in which the same elements as in Figure 1 having the same reference, there is shown an example of application of the invention.

In this example, the access network 4 is the public switched telephone network or PSTN (in English "Public Switched Telephone Network" or PSTN) of the French operator FRANCE TELECOM.

The network access server 31 is located at a point of presence 30 of the operator or POP (from the English "Point Of Presence"). This POP comprises several network access servers for the interconnection to the network 5 of several respective access networks, of the same operator or of different operators. In the example shown, the POP thus comprises another network access server 32 for the interconnection of another access network (not shown) constituted for example by the integrated services digital network or ISDN (in English "Integrated Services Digital Network" or ISDN).

The network 5 is an IP network (from the English “Internet Protocol”). The POP 30, and in particular the network access server 31, make it possible to interconnect the access network 4 to a subnet 5a of the network 5, consisting by the heart of the IP network of the operator FRANCE TELECOM, called "Backbone Network and Internet Collection" or RBCI. It is a backbone network. The function of the NAS 31 is to concentrate the IP information flows collected by the access network 4 towards the first router 51 of the RBCI, called the concentrator node (or NC). The NC concentrates the different IP information flows coming from the various access networks linked to the POP 30, to send them to another RBCI router such as a regional node (or NR) and / or to a transit node ( NT), not shown, whose routing capacities are higher.

In this example, the network 5 also includes other subnets 5b and 5c. The sub-network 5b is the network called "Internet Business Access Network" or RAEI, of the company TRANSPAC, a subsidiary of the operator FRANCE TELECOM. It is also an IP network. The subnet 5c is for example the IP network of any ISP, to which the server 2 of this ISP is connected. The sub-network 5a and the sub-network 5b are interconnected by a router 53. Likewise, the sub-network 5b and the sub-network 5c are interconnected by a router 55.

In this example, moreover, the first service access server 61 is connected to the subnet 5b while the second service access server 62 is connected to the subnet 5b. The servers 61 and 62 are preferably RADIUS servers. In other words, they operate according to the RADIUS protocol defined in RFC 2138. The server 61 is compatible with the PPP and L2TP connection modes but not with the TCP-Raw mode. However, the server 62 is compatible with the TCP-Raw mode. Thus, if we consider that the network 5 and the network access server 31, which is shared, support these three connection modes, the system includes at least one service access server which is compatible with each of these connection modes. It will be noted that for at least some of these connection modes, the system may include several service access servers which are compatible. A user accesses the services of a determined ISP by calling a specific telephone number via a user terminal such as 11, comprising a modem, which is connected to the access network 4. This call is routed to the NAS 31 by the access network 4. A connection according to the IP protocol is established between terminal 11 and the server, such as 2, of the ISP. Depending on the case, this IP connection can be established according to one of several specific connection modes of the access service (s) and / or the ISP. When implemented at the network access server 31, the method according to the invention makes it possible, in this example, to transmit the counting messages and / or the authentication messages associated with the connections in PPP mode or in L2TP mode to the RADIUS server 61, and the counting messages for connections in TCP-Raw mode to the RADIUS server 62 (it is recalled that no authentication message is sent in this latter connection mode). In FIG. 4, the corresponding information flows are symbolized by the broken lines 71, 72 and 73 respectively.

Claims

1. A method of accessing a packet mode network (5) for establishing a connection across the network between a user terminal (11) and a server of a service provider (2), according to a connection mode determined from among a plurality of different connection modes supported by the network (5), comprising the steps consisting in:

- identifying said determined connection mode, from data transmitted by the user terminal (2);

- selecting, as a function of said determined connection mode, at least one service access server from a plurality of service access servers (61, 62), so that the selected service access server is compatible with said determined connection mode;

- transmit at least one connection count message to said selected service access server.

2. Method according to claim 1, characterized in that it further comprises a step consisting in transmitting authentication messages of the connection to said access server to the selected services.

3. Method according to one of claims 1 or 2, characterized in that each connection mode is associated with one or more respective services.

4. Method according to one of the preceding claims, characterized in that it is implemented at the level of a network access server (31).

5. Access server to a packet mode network (5) for establishing a connection between a user terminal (11) and a server of a service provider (2) through the network (5 ), according to a connection mode determined from among a plurality of different connection modes supported by the network (5), characterized in that it comprises:

- means for identifying said determined connection mode, from data transmitted by the user terminal (11); means for selecting, as a function of said determined connection mode, at least one service access server from a plurality of service access servers, so that the selected service access server is compatible with said service determined connection mode; - Means for transmitting at least one connection counting message to said at least one selected service access server.

6. Server according to claim 5, characterized in that it further comprises means for transmitting authentication messages of the connection to said server for accessing the selected services.

7. Server according to one of claims 5 or 6, characterized in that each connection mode is associated with one or more respective services.

8. System comprising a packet mode network (5), at least one user terminal (11), at least one server of a service provider (2), characterized in that it further comprises a plurality of servers of access to services (61, 62) compatible with at least one respective connection mode, as well as at least one network access server (31) according to one of claims 6 to 8, for the establishment of a connection between the user terminal (11) and the server of the service provider (2) through the network (5).

9. System according to claim 8, characterized in that it comprises an access network (4) to which the user terminal (11) is connected, and which is interconnected to the network in packet mode (5) by the server access to the network (31).

10. System according to any one of claims 8 or 9, characterized in that the packet network (5) is an IP network.

11. System according to any one of claims 8 to 10, characterized in that the packet network (5) is a backbone network.

12. System according to any one of claims 8 to 11, characterized in that the service access servers (61, 62) are RADIUS servers.