Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-12-06
2003-12-23
Nguyen, Chau (Department: 2663)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S401000, C370S409000
Reexamination Certificate
active
06667971
ABSTRACT:
BACKGROUND
1. Field of Invention
The present invention relates generally to a system and method for providing computer network services. More specifically, the present invention relates to improving the variety of services offered to users of high speed data access systems, such as asymmetric digital subscriber line (ADSL) systems, and increasing the security involved with providing those services.
2. Background of the Invention
Asymmetric digital subscriber line (ADSL) technology offers significantly higher data rates than conventional modems. With a typical upstream (i.e., from a subscriber) data rate of 256 kilobits per second (Kbps), and a typical downstream (i.e., to the subscriber) data rate of 1.5 megabits per second (Mbps), service providers are able to offer services not possible or practical using traditional modems. These services can provide subscribers with new and more efficient ways of obtaining information and conducting business. It should be noted that even higher data rates than those mentioned above can be achieved with ADSL.
A prior art system
100
using ADSL transport is shown in
FIG. 1
in which a user employs Ethernet access locally. Referring to
FIG. 1
, users using computers
102
a
and
102
b
communicate with a network service provider (NSP)
110
using the increased bandwidth offered by ADSL. Computers
102
a
and
102
b
communicate through internal or external ADSL termination unit-remotes (ATU-Rs)
104
a
and
104
b
respectively. ATU-Rs
104
a
and
104
b
convert data from computers
102
a
and
102
b
respectively into ATM format and forward the data to a digital subscriber line access multiplexer (DSLAM)
106
using ADSL transport. A single DSLAM, for example, the A1000 DSLAM offered by Alcatel, can terminate 576 loops. Other DSLAMs can terminate different numbers of loops, depending on the apparatus and technology used.
DSLAM
106
terminates the ADSL transport signal, and forwards the data (in ATM format) to a network, e.g., ATM network
108
, using DS3 or OC-3 signal transports. DS3 and OC-3 are well-known signal formats for transporting data through ATM network
108
. The data is forwarded to NSP
110
by (or through) ATM network
108
. Conventionally, ATM network
108
is a wide-area network using fiber optic data communication links. Communication with NSP
110
is done using ATM formatting over SONET, DS3, or DS1 transport.
As illustrated by the protocol stack
112
in
FIG. 1
, data from user computer
102
a
is transmitted to ATU-R
104
a
in Internet Protocol (IP) format using an Ethernet local network. That data is formatted by ATU-R
104
a
into ATM format for transmission to NSP
110
. Data is transmitted from ATU-R
104
a
to DSLAM
106
using ATM cells. DSLAM
106
switches the ATM cells and directs them to the ATM network
108
. On the receiving side, the data is forwarded to NSP
110
using ATM cells over DS1, DS3 or OC-3 links. When the ATM cells reach NSP
110
, they are reassembled to form Internet Protocol (IP) packets and distributed to the appropriate server via IP. As illustrated in
FIG. 1
, a permanent virtual circuit (PVC)
114
is established between user computer
102
a
and NSP.
110
to direct the ATM cells appropriately. As shown in
FIG. 1
, ATM cells are sent on the PVC established between user computer
102
a
and NSP
110
(and from NSP
110
to user computer
102
a
) using the AAL5 protocol.
The term “permanent virtual circuit” (PVC) is ATM terminology for a virtual (logical) connection that has a well-defined origin, a well-defined destination, and a unique identification. A virtual connection converts a physical address corresponding to a physical origin and a physical destination of the connection to a unique connection identification representative of the physical path from the origin to the destination of the connection. ATM cells are injected into a PVC at its origin, and transported over the PVC to the destination. Thus, a PVC is an example of a logical connection from a physical origin to a physical destination of the connection. The actual physical route over which the ATM cells travel can be complex. Using the term PVC reduces the complexity to a virtual concept, which is easier to conceptualize and discuss. ATM and other communication systems are described in more detail in Andrew S. Tanenbaum,
Computer Networks
, Prentice-Hall (3
rd
Ed. 1996), which is incorporated by reference herein in its entirety.
System
100
is an example of a conventional single PVC system. Conventional single PVC systems suffer from at least one serious drawback. Such systems use a dedicated PVC between the user and the NSP. However, other NSPs can be attached to ATM network
108
. For example, Internet Service Providers (ISPs), corporate networks and campus networks can be attached. Because the PVC is dedicated to a specific NSP, it is difficult for a subscriber to choose between different NSPs. To do so, the subscriber must call the ADSL service provider, e.g., a telephone company or NSP, and have the PVC dedicated to a different NSP. This is time consuming, costly and inconvenient for the subscriber, the telephone company and the service provider.
Thus, the conventional architecture severely limits the subscriber's choice of NSPs as well as the subscriber's choice of the services the NSPs provide. Users desiring services only offered by one NSP, as well as other services offered by another NSP, are not able to get both sets of services using system
100
unless the NSPs have a tunneling agreement (described below) in place. Moreover, because NSPs must offer virtually all services that a particular subscriber desires, they are less able to offer specialized services more tailored to specific subscriber's needs, and for which they may have particular expertise.
One solution to this problem has been the use of tunneling arrangements. Through tunneling arrangements, NSPs reach agreements so that a user of one NSP's services can have access to another NSP's services through the first NSP. This solution is not optimal for a number of reasons. For example, the freedom that users have to choose a particular NSP is limited to those having tunneling arrangements in place. In addition, the burden on the first NSP's system, when there are many users trying to tunnel to other NSPs, can degrade the performance of the first NSP's system.
A more robust solution to the problem is to add a service gateway
202
as shown in system
200
in FIG.
2
. Referring to
FIG. 2
, system
200
has essentially the same structure as that of system
100
with the addition of service gateway
202
and optional proxy AAA system
204
. Service gateway
202
and proxy AAA system
204
allow users to select any of the NSPs, for example, NSP
110
, NSP
206
or NSP
208
to obtain computer network services.
Service gateway
202
performs a second desirable function. It aggregates all the users desiring to communicate with a particular NSP onto a single PVC pipe. The single pipe carries all the data to or from the NSP. This is important because many ATM devices (including ATM switches and NSP routers) do not have sufficient ports to support large numbers of ATM PVCs. This aggregation decreases the complexity on the NSPs' routers, lessens the burden on personnel and systems responsible for configuring, maintaining and monitoring the ATM connections, and allows NSPs to request the type of ATM pipe, or pipes, that best meet their need to balance cost and quality of service (QoS). The details of provisioning and session management for this architecture are described in K. R. Frank, et al., “Fast Access ADSL Architecture Description,” TM-ATSEC-01-98-084, which is incorporated by reference herein in its entirety.
The protocol stacks described above with respect to system
100
are also used in system
200
, except that some changes are made at service gateway
202
to accept and evaluate the address (i.e., which NSP) to which to route the session. Further, service gateway
202
performs IP forwarding to send the m
Fowler, Jr. Henry J.
Modarressi Abdi R.
BellSouth Intellectual Property Corporation
Juntima Nittaya
Nguyen Chau
Shaw Pittman LLP
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