An asynchronous transfer mode (ATM) network is a connection-oriented network which is well suited for high speed, high volume data communications. An ATM network consists essentially of a plurality of computers (hosts) which are connected in communicating relationships by a plurality of ATM switches. To provide communication between one computer and another, one or more virtual channel connections are established between the computers via the switches. Information (data) to be transferred is reduced into standard size units or cells, transmitted via the virtual channel connections, and reassembled at the point of exit from the ATM network. As a result of the virtual channel connections and channel identification information which accompanies each transmitted cell, an ATM switch is not required to perform substantial work to determine through which one of its ports a particular cell should be retransmitted.
While ATM represents a superior solution in terms of efficient use of bandwidth and transmission speed, much of the world's existing data network infrastructure consists of hosts connected to local area networks (LANs) which operate in accordance with a "connectionless" protocol such as Ethernet or Token Ring. In a connectionless LAN, when two hosts are communicating with each other there is no logical communication path which exists for the duration of their communication. Instead, frames of information, each of which includes a source address which identifies the host from which the frame originated and a destination address which identifies the host for which the frame is intended, are transmitted over a shared medium at particular times, in accordance with the rules of the protocol. Each source or destination address, which is known as a media access control (MAC) address, is essentially a number which uniquely identifies a particular host served by the LAN.
As a frame traverses the LAN, it may encounter a bridge, router or other LAN interconnection devices which, upon receipt of the frame, must examine or analyze the addresses contained therein to determine whether that particular frame should be retransmitted and, if so, through which particular output port in order to reach the intended destination. As a result, a substantial amount of work must be frequently performed by such LAN interconnection devices, thus significantly reducing efficiency and transmission speed.
In order to enable the vast numbers of LAN-connected users to obtain the benefits of ATM technology, a communication technique known as LAN Emulation over ATM (LANE) was developed. LANE is a method of emulating a connectionless LAN segment over an ATM network. LANE supports communications between two hosts where both hosts are connected directly to an ATM network, where one host is connected directly to an ATM network and the other is connected by a LAN segment to an ATM-LAN bridge, or where the hosts are connected to different LAN segments and both segments are connected to an ATM network. As specified by LANE, a host runs a software process called a LAN Emulation Client (LEC) to effect LAN-emulated communications over the ATM network. However, LANE does not provide for the association of multiple LECs with a single host, redundancy against the failure of a LEC (or its associated network interface card), nor for a scaleable bandwidth interface between a host and the ATM network.