Apparatus and method for a remote access server

A remote access server and method for using the remote access server in a packet network. In one embodiment, the remote access server includes a packet switch fabric, a packet network server and a dial access server. The packet network server has a first port for sending and receiving packet-based signals with the packet switch fabric and a second port for sending and receiving packet-based signals with the packet network. The dial access server has a port for sending and receiving packet-based signals with the packet switch fabric and the dial access server has a first digital signal processor for performing signal processing on the packet-based signals. The packet switch fabric transfers packet-based signals among the packet network server, and the dial access server. In a further embodiment, the dial access server includes a second digital signal processor for performing signal processing on the packet-based signals. The first digital signal processor may be a channel signal processor and the second digital signal processor may be a packet protocol processor. The signal processors perform remote access signal processing. The packet protocol processor may perform dial-up Internet protocol support. The channel signal processor may perform modulation and demodulation of packet-based signals, transcoding of packet-based signals, and automatic modem adaptation.

TECHNICAL FIELD
 The present invention relates to networks and, more specifically, to remote
 access servers connecting to packet networks.
 BACKGROUND ART
 FIG. 1 shows a system diagram of typical remote access servers (RAS) 2 and
 the interconnections for connecting a subscriber to the Internet.
 Currently, dial-up Internet access is provided to a subscriber through a
 remote access server typically located within the local calling area of
 the subscriber and maintained by either an Internet Service Provider (ISP)
 or a local or inter-exchange carrier on behalf of an ISP. A subscriber
 using a personal computer 4 dials into the remote access server 2 via a
 modem (not shown) and initiates a setup with the remote access server 2.
 The call travels from the subscriber's modem to the telephone company's
 end office (EO) 6 which routes the call to the remote access server 2. The
 remote access server 2 identifies and verifies that the subscriber is
 permitted to make a connection and have access to the Internet during
 setup. The subscriber may then send and receive data with the Internet 8.
 The remote access server 2 provides the connection between the
 circuit-based network of the telephone system 3 and the packet-based
 network of the Internet 8. One drawback of this configuration is that it
 requires the deployment of remote access servers 2 in close proximity to
 the ISP subscribers, in order to avoid long distance or toll charges for
 the subscriber, thereby making upgrades and repairs difficult for an
 Internet service provider.
 FIG. 2 illustrates the architecture of a prior art remote access server 2.
 The remote access server 2 receives telephone calls from the telephone
 network 3 into a circuit network server 12. The circuit network server
 passes the circuit-based signals of each telephone call to a dial access
 server 14 via a circuit switch fabric 13. The dial access server 14
 demodulates the voice-band data of the circuit-based signals and extracts
 the Internet Protocol (IP) packets for routing to the appropriate Internet
 destination. The packets are passed to a packet network server 16 via a
 packet switch fabric 15. From the packet network server 16 they are
 distributed into the packet network 8. It is well known that a packet
 switch fabric 15 can be implemented with a variety of technologies, such
 as an arbitrated packet bus or a centralized switching module. The dial
 access server 14 uses the packet switch fabric 15 to move the extracted IP
 packets to a packet network server 16 and the associated packet network
 interface appropriate for delivering the packet to its intended
 destination. The architecture of FIG. 2 carries the cost and complexity
 burden of two separate and independent switch fabrics: one circuit and one
 packet. In addition, the time division multiplexed structure of circuit
 network interfaces make them more costly at higher rates than the
 corresponding packet network interfaces.
 SUMMARY OF THE INVENTION
 The invention provides, in a preferred embodiment, a remote access server
 and method for using the remote access server in a packet network. In one
 embodiment, the remote access server provides a packet switch fabric, a
 packet network server and a dial access server. The packet network server
 has a first port for sending and receiving packet-based signals with the
 packet switch fabric and a second port for sending and receiving
 packet-based signals with the packet network. The dial access server has a
 port for sending and receiving packet-based signals with the packet switch
 fabric and the dial access server has a first digital signal processor for
 performing signal processing on the packet-based signals. The packet
 switch fabric transfers packet-based signals among the packet network
 server, and the dial access server. In a further embodiment, the dial
 access server further includes a second digital signal processor for
 performing signal processing on the packet-based signals.
 The first digital signal processor may be a channel signal processor and
 the second digital signal processor may be a packet protocol processor.
 The signal processors perform remote access signal processing. The packet
 protocol processor may perform dial-up Internet protocol support. The
 channel signal processor may perform modulation and demodulation of
 packet-based signals, transcoding of packet-based signals, and automatic
 modem adaptation.
 In other embodiments the packet switch fabric may include a switching
 module, a packet bus or a cell bus.
 The remote access server may further include a management server coupled to
 the packet switch fabric providing management of remote access server
 resources where the packet switch fabric also transfers packet-based
 signals to the management server.
 In another embodiment the remote access server includes an interface module
 for receiving and sending packet-based signals having embedded information
 packets and sending and receiving the embedded information packets. The
 server also includes a modem module for receiving the packet-based signal,
 performing demodulation on the packet-based signal, and extracting the
 embedded information packets or receiving the information packets and
 creating a packet-based signal with embedded information packets. The
 server further includes a packet switch fabric enabling transfer of the
 packet-based signal and the embedded information packets among the
 interface module and the modem module.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
 The word "packet" as used herein defines a block of data with a header. The
 term packet includes cells. A packet header typically includes
 information, such as, source and destination addresses or a connection
 identifier. The header is used to direct the packet through the packet
 network. The term "digital signal processor" as used herein shall refer to
 a processor which is capable of manipulating a digital signal including
 packets. The term "packet switch fabric" as used herein refers to any
 device which contains the means to transfer packets between two or more
 devices, a packet switch fabric may be, but is not limited to, a packet
 bus, a switching module, a cell bus, a crossbar switch, a space division
 switch or a signal router. The term "multiplexer" shall refer to any
 device, which may perform multiplexing, demultiplexing, or both
 multiplexing and demultiplexing functions. The term "transcoding" refers
 to the process of transforming a signal from one state of coding to
 another. The term "circuit-based signal" refers to a data stream in a
 time-division multiplexed path containing digital information. The term
 "packet-based signal" refers to a data stream containing packets, wherein
 the packets contain digital information. The term, "packet adaptation"
 refers to the process of segmenting a circuit-based digital signal
 composed of samples and creating a packet from each segment by adding a
 header to form a packet-based signal. Packet adaptation also refers to the
 process of removing the header information from a packet and reassembling
 the packets to recreate the circuit-based digital signal. Packet
 adaptation may further include the process of time stamping. Hereinafter
 both special purpose digital signal processors and general purpose digital
 signal processors shall be referred to as digital signal processors
 (DSPs). The term "port" shall refer to any input or output. Aport may
 include multiple inputs and multiple outputs. The term "remote access
 signal processing" refers to signal processing that is performed on a
 remote access server such as transcoding, modulating and demodulating data
 including support for modem standards, automatic modem adaptation, dial-up
 IP support, virtual private network (VPN) security and routing based on
 the dialed number or user ID. The term "channel signal processing" as used
 herein shall mean support for modem standards such as V.90, V.34bis, V.34,
 V.32bis, V.32, V.27 ter, V.22bis, V.22, V.21, Bell 212A, and Bell 103,
 along with V.42bis data compression, and MNP and MNP10-BC error correction
 for cellular connections. The term "packet protocol processing" as used
 herein shall refer to support for data protocols such as point-to-point
 protocol (PPP), serial line Internet protocol (SLIP), compressed serial
 line Internet protocol (CSLIP), TELNET, dynamic Internet Protocol (IP)
 address assignment, multilink PPP (MP), STAC/MS-STAC compression, and RFC
 1144 TCP Header compression, along with support for user authentication
 and user service profile determination, such as, remote authentication
 dial-in user service (RADIUS), terminal access control system (TACACS),
 TACACS+challenge handshake authentication protocol (CHAP), password
 authentication protocol (PAP), and DIAMETER. The term packet protocol
 processing also refers to IP routing and forwarding based on IP addresses
 or other packet header information.
 FIG. 3 shows an overview of a system for reducing the number of remote
 access servers 30 used for making dial-up access services available in
 accordance with one embodiment of the invention. An Internet subscriber,
 using a personal computer (PC) palm PC or other computing device 4,
 initiates a connection to an Internet Service Provider (ISP) through a
 dialed telephone call requesting a connection to a server or other
 subscriber within the Internet or other packet-based network. The
 subscriber is connected to an end office (EO) switch 6. The connection to
 the end office may take the form of an analog modem (not shown) attached
 to an analog line or the connection may be via an Integrated Service
 Digital Network (ISDN) modem (not shown) attached to an ISDN line. The
 dialed number of the ISP causes the EO circuit switch 6 to direct the call
 to a gateway 32 through the digital trunks 38 interconnecting the gateway
 to the EO switch 6. The dialed number may be used by the gateway 32
 through a call routing table look-up to initiate a call set-up directly
 with the remote access server 30. Alternatively, the dialed number may
 provide the user with several service options offered by different server
 elements (e.g., FAX in addition to the remote access server) within the
 gateway itself or attached to the Internet Protocol (IP) backbone 8. Here
 the user may be prompted with an interactive voice response (IVR)
 application to select a service by entering dual tone multi-frequency
 (DTMF) digits in response to voice prompts. Based on the user selected
 service, the call is forwarded to a service element that offers that
 service. Included here is the remote access server service, and, if
 selected, the gateway 32 directs the call to the remote access server 30
 using a call signaling protocol such as International Telecommunications
 Union (ITU) recommendation H.323 or Internet Engineering Task Force (IETF)
 Session Initiated Protocol (SIP). When the call set-up is processed at the
 remote access server 30, resource management functions within the remote
 access server 30 will ensure that sufficient resources exist to service
 the call before the call is allowed to go through. If there are sufficient
 resources, such as an appropriate dial access server within the remote
 access server 30, the resources will be assigned to the call and the
 remote access server 30 will acknowledge the gateway's request and
 indicate that the call can be accepted. The gateway 32 in turn will
 respond to the EO switch 6, which will put the call through to the remote
 access server 30.
 An application running on the PC 4 creates information packets with the
 address of a destination server. The analog or ISDN modem embeds the
 information packets into the circuit-based connection for transmission
 first to the EO switch 6 and then to the gateway 32. In a preferred
 embodiment the embedded information packets are embedded IP packets. At
 this point, the gateway 32 converts, for the call, the circuit-based
 digital signal from its circuit network interface to the EO switch 6 to a
 packet-based signal by a standards-based packet adaptation protocol such
 as the IETF Real Time Protocol (RTP). The routers 34 and/or switches in
 the IP Backbone 8 forward the packet-based signal to a packet interface 31
 of the remote access server 30. Based on an IP address of the remote
 access server 30 and user datagram protocol (UDP) port number within the
 packet headers of the packet-based signal carrying the embedded
 information packets for the call, the packet-based signal packets are
 directed within the remote access server to the dial access server
 assigned during call set up. For Internet services, the remote access
 server performs channel signal processing and packet protocol processing.
 The user now has full Internet access through the remote access server.
 In one embodiment of the invention, the remote access servers are composed
 of multiple packet network servers 42 and multiple dial access servers 46
 all coupled to a packet switch fabric 44, as shown in FIG. 4. Each server
 may be designed as a combination of integrated circuits and other
 components and placed on an individual integrated circuit card or module
 for insertion into a module receptor board. The packet switch fabric 44
 may also be implemented as a module when the packet switch fabric 44 takes
 the form of a signal switcher, a router, or a packet bus with interface
 circuits.
 In an embodiment, a remote access server includes packet network servers 42
 which receive the packet-based signals from the packet network 36, and
 dial access servers 46 which extract the embedded information packets
 within the packet-based signals and direct the information packets to
 their final destination within the packet network 36. The packet network
 36 may be the IP backbone of the Internet 8 or another packet-based
 network such as a packet-based intranet. The packet network servers 42 and
 the dial access servers 46 are linked with a packet switch fabric 44 in
 such a way that a packet-based signal may be directed between any two
 servers. Once the dial access server 46 has determined the destination of
 the embedded information packets, the information packets are directed to
 the appropriate packet network server 42 and then redirected into the
 appropriate packet network 36. In such an embodiment, Internet Service
 Providers need not have a remote access server 30 for every local calling
 area of the telephone system 3. Remote access servers 30 may be
 distributed throughout the packet network 36 in convenient locations for
 the Internet service providers, so that upgrades and maintenance may be
 performed more easily.
 The packet switch fabric 44 transfers packet-based signals and information
 packets among packet network servers 42, and dial access servers 46. In an
 embodiment of the invention, the packet switch fabric 44 may be a packet
 bus. In another embodiment, the system may operate on ATM cells and the
 packet switch fabric 44 would be a cell bus. Packet network servers 42 and
 dial access servers 46 would be configured to handle cells in such an
 embodiment. The switching fabric within the remote access server which
 connects the packet network servers and the dial access servers may be
 implemented with a circuit switch fabric in an alternative embodiment. In
 such an embodiment, the packet network server performs packet adaptation
 converting the incoming packet-based signals into circuit based signals
 and the dial access servers are so equipped as to receive circuit based
 signals.
 The remote access server may further include a management server 48 The
 management server 48 has overall responsibility for the management of
 resources including routing of the signals to the requested packet network
 and assignment of the appropriate dial access server. The management
 server 48 coordinates the overall operation of the remote access server,
 including the booting of the gateway on powerup, configuration of the
 gateway resources, recovery from component failures, and reporting of
 events, alarm and billing information to an external network management
 system (not shown).
 In an embodiment of the invention, each packet network server 42 (see FIG.
 5) interfaces to a packet bus 50 via a packet bus interface 52 for sending
 and receiving packets to other packet network servers 42 or dial access
 servers 46, and interfaces to the packet network 36 by standard packet
 network interfaces 56 such as Ethernet. The packet network server 42
 performs the packet switching functions of address lookup and packet
 forwarding. The address lookup and packet forwarder 54 may analyze the
 packet header to identify the assigned resources for the connection and
 may strip the IP and UDP header and insert an internal remote access
 service connection identifier for the packet-based signal. An Ethernet
 Medium Access Control (MAC) device 56 controls access to the packet
 network interface. A physical interface 58 or port provides the connection
 between a line in the packet network 36 and the remote access server 30.
 The physical interface 58 may be, but is not limited to, a coaxial
 interface, or a twisted pair interface for 10-base-T or 100-base-T
 connections.
 The dial access server of FIG. 6, in accordance with one embodiment of the
 invention, connects to a packet bus through a packet bus interface 62. In
 this embodiment, the dial access server contains two processors, a channel
 signal processor 64 and a packet protocol processor 66. The packet bus
 interface 62 directs the packets for the call to the channel signal
 processor 64 assigned during call set up. For an analog modem call, the
 channel signal processor 64 takes the arriving packet-based signal and
 demodulates the data, included here is support for automatic modem
 adaptation, modulation and demodulation, modem standards, transcoding
 including data compression, and error correction. For an ISDN modem call,
 the channel signal processor 64 extracts the digital data directly from
 the packet-based signal. The channel signal processor 64 forwards the
 digital data to the packet protocol processor 66 which provides support
 for data protocols.
 The packet protocol processor 66, in coordination with the management
 server 48 of FIG. 4, provides dial-up Internet protocol support for user
 authentication and user service profile determination via protocols. Some
 basic security may be provided by Callback and Calling Line ID services or
 other authorization/authentication mechanisms such as PAP, CHAP, RADIUS
 and DIAMETER. The packet protocol processor 66 also provides the IP
 forwarding function for the embedded information packets. For example,
 selecting which packet interface the information packets should use to
 exit the remote access server 30 into the IP backbone 36. The IP backbone
 36 may be the same or different than that from which the packet-based
 signal originally arrived to the remote access server 30. Packet
 interfaces may include local area networks (LAN) such as, Ethernet or wide
 area networks (WAN) such as, Frame Relay, asynchronous transfer mode (ATM)
 or synchronous optical network (SONET), and may support secure tunneling
 such as with the Point-to-Point Tunneling Protocol (PPTP) or L2TP.
 Although various exemplary embodiments of the invention have been
 disclosed, it should be apparent to those skilled in the art that various
 changes and modifications can be made which will achieve some of the
 advantages of the invention without departing from the true scope of the
 invention. For example, internal processes within the remote access server
 may be achieved with circuit-based signals, however the signals which
 enter the remote access server and leave the remote access server are
 packet-based. These and other obvious modifications are intended to be
 covered by the appended claims.