IL124695A

IL124695A - Protocol for group address services for a connection oriented network providing lan emulation

Info

Publication number: IL124695A
Application number: IL12469598A
Authority: IL
Original assignee: 3Com Corp
Priority date: 1997-05-29
Filing date: 1998-05-29
Publication date: 2002-03-10
Also published as: IL124695A0; GB9811636D0; GB2327561A; GB2327561B

Abstract

In a connection oriented network which provides emulation of one or more variant network protocols for end systems coupled to edge devices on the connection oriented network, a method for managing transfer of a multiple destination packet having a group address specified at a network layer or above received at incoming ports on edge devices on the connection oriented network, comprising: determining the group addresses for which end systems coupled to the edge devices are listening; identifying the group address carried in a particular multiple destination packet; and transmitting via the connection oriented network the multiple destination packet to end systems listening for multiple destination packets having the identified group address of the multiple destination packet.

Description

PROTOCOL FOR GROUP ADDRESS SERVICES FOR A CONNECTION ORIENTED NETWORK PROVIDING LAN EMULATION LAN ii'^mx Eitan, Pearl, Latzer & Cohen-Zedek Advocates, Notaries and Patent Attorneys P-1703-IL PROTOCOL FOR GROUP ADDRESS SERVICES FOR A CONNECTION ORIENTED NETWORK PROVIDING LAN EMULATION Inventor: Jeffrey J. Krause CROSS REFERENCE TO RELATED PATENT The present application is related to U.S. Patent No. 6,005,864 entitled Protocol for Optimized Multicast Services for a Connection Oriented Network Providing LAN Emulation, invented by Jeffrey J. Krause, filed 14 July, 1995.

BACKGROUND OF THE INVFNTTON Field of the Invention The present invention relates to protocols for interconnecting networks using connection oriented protocols, such as asynchronous transfer mode (ATM), with networks using connectionless protocols, such as Ethernet or Token Ring; and more particularly to improving performance of such systems for group addressed messages including multicast and broadcast messages.

Description of Related Art ATM is an emerging network standard based on a connection oriented network protocol. In order to transmit data between users of an ATM network, a connection is first set up between the users, and then a point to point transmission of the data is accomplished from the source through an ATM switch to the destination. When ATM switches are used to provide data connectivity for personal computers and other network devices, a number of problems occur when running networking software such as Novell IPX, TCP/IP - 1 - Attv Docket No: 15886.870 l:\HOME\MAHVCLlENT\l 5886\870\PATAPPL.870 PROTOCOL FOR GROUP ADDRESS SERVICES FOR A CONNECTION ORIENTED NETWORK PROVIDING LAN EMULATION Inventor: Jeffrey J. Krause CROSS REFERENCE TO RELATED APPLICATION The present application is related to co-pending U.S. Patent Application entitled Protocol for Optimized Multicast Services for a Connection Oriented Network Providing LAN Emulation, invented by Jeffrey J. Krause, Application No.: 08/502,871; filed 14 July 1995.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to protocols for interconnecting networks using connection oriented protocols, such as asynchronous transfer mode (ATM), with networks using connectionless protocols, such as Ethernet or Token Ring; and more particularly to improving performance of such systems for group addressed messages including multicast and broadcast messages.

Description of Related Art ATM is an emerging network standard based on a connection oriented network protocol. In order to transmit data between users of an ATM network, a connection is first set up between the users, and then a point to point transmission of the data is accomplished from the source through an ATM switch to the destination. When ATM switches are used to provide data connectivity for personal computers and other network devices, a number of problems occur when running networking software such as Novell ΓΡΧ, TCP/IP - 1 - Attv Docket No: 15886.870 I.\HOME\ AH\CLIENT\15886\870\PATAPPL.870 or Xerox XNS protocols existing on the installed network PCs and servers. These network layer protocols are designed to run on a connectionless type local area network, such as Ethernet, Token Ring, or FDDI networks where the packets are placed on the network fabric and heard by all other end stations on the LAN. To provide connectivity among these network types, vendors of ATM equipment have agreed upon a set of conventions and standards called LAN emulation. A standards body which manages the ATM specification, called ATM Forum, has published a document entitled LAN Emulation Over ATM Specification, which is incorporated by reference herein.

One primary problem that LAN emulation addresses is that most network software, based on network layer protocols, such as Netware IPX, Xerox XNS, TCP/TP, AppleTalk, and OSI, use an end to end path, medium access control (MAC) address identification technique based on broadcast or multicast packets. When an end station A wants to communicate with another end station B, the first end station A issues a multicast packet to the network which is heard by all other end stations in the same multicast domain. Based on some higher layer information in the packet, such as user name or server name, the end station B recognizes that it is the one that should respond and does so with a unicast packet to the original end station A. This works effectively in Ethernet, Token Ring, and FDDI networks, where packets are placed on a network fabric and are heard by all other end stations. This is analogous to a person, Sarah, in an open room full of other people yelling out "This is Sarah, is Joe here?", and having Joe hear that call and answer back, "Yes, Sarah, I'm here." Then the conversation can occur between the two at that point.

However, an ATM environment does not work in the same fashion. In this environment, packets are sent only to a single destination at the MAC layer. No other device in the network has access to the data except the recipient. The originator of the data packet, end station A, must know the ATM path address of the recipient end station B, prior to sending the packet. This is analogous to a person, Sarah, being in a closed room with a phone and wanting to talk to Joe. - 2 - Attv Docket No: 15886.870 l:\HOME\MAH\CUENT 5886\870\PATAPPL-870 Sarah must know Joe's phone number and dial it to talk to Joe. The problem with this connection oriented method is that in most existing network environments, the installed end stations are running software which is not capable of knowing the address in advance of each other end station it might want to communicate with. The LAN emulation standard published by the ATM Forum addresses this problem by providing a higher layer set of services that emulate the behavior of a shared medium local area network, such as Ethernet. These services include a LAN emulation configuration server (LECS), a LAN emulation server (LES), and a broadcast and unknown server (BUS). The LECS contains a list of all the ports on the edge devices (network intermediate system devices that connect end systems or non-ATM intermediate system devices to the ATM network fabric) on the network. For each port on each edge device, the LECS identifies the multicast domain (also referred to as a virtual LAN), of which devices connected to that port are members. In addition, it identifies the LES and BUS servers that might be used for each port on the edge device. When an edge device is initialized or reset, it queries the LECS for this information.

The LAN emulation server LES is used by the edge device connecting a particular end station to the ATM network. When it is initialized, the edge device queries the LECS to find out which LES to connect to, and then whenever it gets a unicast packet from the end station, the edge device queries the LES to find out the ATM path address of the destination in the system. That address is then used to route the packet through the ATM switches.

The broadcast and unknown server BUS is used when an edge device receives a broadcast or a multicast packet from an end station, or when it receives a packet with a destination address that is not identified by the LES. When such a packet is received, the edge device sends the packet to the BUS. The BUS then identifies all other end stations which are configured as part of the same multicast domain, and sends the packet to all end systems that are part of the same multicast domain. Using the same analogy as above, Sarah calls BUS, - 3 - Atty Docket No: 15886.870 I:\HO E\M AH\CLIENTM 5886«70\PATAPPL.870 saying she wants to talk to Joe in Santa Clara, California, and then BUS dials every phone number in Santa Clara leaving a message that Sarah wants to talk to Joe, and leaving her phone number. Joe, along with everyone else, gets the message, and then calls Sarah back and has a conversation with her.

The approach to broadcast and multicast messages adopted by the LAN emulation standard for ATM helps in forwarding multicast messages to all stations, and relies upon filtering at the end stations as is done in existing LANs. However, a relatively large number of end stations do not need to receive the broadcast or multicast messages. Particularly, some end stations within a single multicast domain may not be using the same network level software which generated the multicast message, or may not be running applications listening for the same set of multicast messages.

Thus, the problem of handling multicast addresses on a connection oriented network creates unnecessary traffic which can be significant. Prior attempts to solve this problem have been based on the creation of virtual LANs which segment the multicast traffic based on virtual LAN identifiers. Other approaches include rewriting the application layer programs in use so that they are connection oriented. Yet another approach involves increasing bandwidth of switches involved in the network to compensate for the increase in multicast traffic. However, virtual LANs have a high management overhead. Rewriting connectionless applications is expensive and not practical given the large number of them that are in existence. Increasing switch bandwidth is also expensive to customers and does not directly address the problem of consuming bandwidth of connection oriented networks by emulated multicast addresses.

Thus, it is desirable to provide a service which can intercept these messages, and forward them directly to their destinations, instead of broadcasting them to every station. - 4 - Attv Docket No: 15886.870 I:\HOME\M AH\CLIENT 15886\870\PATAPPL.870 SUMMARY OF THF. TNVF.NTTON The present invention provides an enhanced BUS server in the ATM architecture, or other group address server in a network, which works by learning group addresses for which end stations on the ports of edge devices have registered, and by tying that information to MAC layer address tables to avoid sending multicast and broadcast packets or other group or multidestination packets to end systems that have not registered for the particular group address. According to the present invention, the system configures multidestination registration information about every end system attached to the network, and filters packets based on this information at the group address server level.

Present invention is applicable in one advantageous environment to connection oriented networks which provide emulation of one or more variant network protocols for systems coupled to edge devices on the connection oriented networks. Thus, for example, the Asynchronous Transfer Mode (ATM) LAN emulation environment is particularly suited to the present invention.

According to one aspect of the invention, it can be characterized as a method for managing transfer of multidestination packets having group addresses, specified at a network layer or above, received at incoming ports on edge devices of a connection oriented network. The method includes determining the group addresses for which end systems coupled to the edge devices on the connection oriented network are listening. The group address which is carried in a particular multidestination packet, is identified. That packet is transmitted via the connection oriented network to end systems which have registered for the identified group address. This results in a management of the distribution of multidestination packets so that circuits in the connection oriented network are not consumed between the server for multidestination packets, and the end systems that do not listen for the identified group address. The performance of the connection oriented network, and the overall network system is significantly improved. - 5 - Atty Docket No: 15886.870 I:\HOMEWAH\CLIENT 5886\870\PAT APPL.870 Thus, according to other aspects of the present invention, the process includes establishing a list of group addresses for end systems accessible through edge devices on the connection oriented network. This list of group addresses is established, for example, by a step executed on the end systems. This step comprises sending to a server for the connection oriented network notice of group addresses for which the end systems are listening. The list of group addresses is maintained in the server in response to the notice.

For example, according to another aspect of the invention, end systems include a protocol stack, and a process coupled with the protocol stack is included that detects registration in the protocol stack at the network layer, that a function in the end system processes packets having a particular group address. In response to detection of the registration, notice indicating the particular group address is sent from the end system to a server on the connection oriented network.

According to another aspect of the invention, the process of sending a multidestination packet comprises, first, sending a multidestination packet from an end system using a connectionless protocol to an edge device coupled to the connection oriented network. At the edge device, the multidestination packet is sent via the connection oriented network to a server for the connection oriented network. The server executes the steps of identifying the group address carried in a particular multidestination packet, and transmitting via the connection oriented network the multidestination packets to end systems which are listening for the particular group address. In one advantageous implementation, according to the present invention, the server which executes the determining and transmitting steps comprises a broadcast and unknown server BUS function specified according to the LAN emulation standard for ATM networks.

According to other aspects of the present invention, additional multicast filtering techniques can be utilized. For example, the network protocols not in use on end systems coupled to particular ports of edge devices can be determined. Multidestination packets are transmitted to ports of edge devices - 6 - Atty Docket No: 15886.870 I:\HOME\ AH\CLIENT\15886\870\PATAPPL.870 other than ports for which the determined network protocol is not in use by systems accessible through the ports. Status is stored for the ports on the edge devices which indicate the protocols in use by systems accessible through the respective ports. In this way, for network protocols in which group address registration is not implemented for multicast management as specified above, filtering can nonetheless be executed on a network protocol basis.

An additional feature allows further filtering based on emulated network membership, commonly referred to as "virtual LAN membership".

According to preferred aspects of the present invention, the group addresses for which the multidestination management is carried out, according to the present invention, comprise Internet Protocol (IP) addresses. According to another aspect, the group address comprises a Transport Control Protocol (TCP) socket identifier over an EP address.

According to another aspect of the present invention, it can be characterized as method for managing transfer of multidestination packets received at edge devices on a connection oriented network. The method includes reporting to a server for the connection oriented network, the group addresses in use by end systems accessible through edge devices on the connection oriented network. Status information is stored at the server in response to the step of reporting for end systems accessible through the edge devices, the status information including an indication of group addresses in use by the end systems. This information includes, for example, a mapping of a port number on a edge device to a group address list. Alternatively, a mapping from a data link layer addresses, such as Medium Access Control (MAC) address, of the end systems to a group address list is utilized. Next, the method includes sending via the connection oriented network a multidestination packet from an edge device which receives the multidestination packet at an incoming port to the server for the connection oriented network. At the server, the group address of the multidestination packet is determined. Next, the server transmits via the connection oriented network the multidestination packet to end systems for - 7 - which the status information indicates that the determined group address is in use by such end systems.

According to yet another aspect of the present invention, a network interface for an end system is provided. The network interface includes a data link layer process that is executed in the end system which filters physical network packets for reception by the end system. Also, a network layer process executed in the end system is provided. The network layer process is coupled with a data link layer process and filters the received physical layer packets at a network layer to select network layer packets for processing by the end system. An application layer process is also executed in the end system. The application layer process is coupled with a network layer process, and processes the selected network layer packets. A registration process in the end system registers network layer group addresses with the network layer process to enable selection of a network layer packets having a network layer group address requested by a higher layer process, such as an application layer process.

Resources are coupled with the registration process to notify a server coupled with the network that the network layer group address is registered with the network layer in the end system. In a preferred embodiment, the resources to notify the server include the process to send an notification packet to an agent for the server, such as an edge device for a connection oriented network providing LAN emulation. The edge device forwards the notification packet to the server where a list of group addresses is associated with the end system.

According to alternative aspects of the present invention, the registration process included in the network interface comprises an element of the application layer process and an element of a network layer process. Thus, when the registration process registers a group address, the interface comprises an intercept process which intercepts the registration command, produces a notification packet, and returns processing to the network layer process to complete registration of the group address. According to another aspect, the - 8 - Att Docket No: 15886.870 l:\HOMEV AH\CLIENTM5886\870\PATAPPU870 resources which notify the server comprise an element embodied with the network layer driver.

Accordingly, the present invention provides a technique by which to gather information about group addresses from end stations themselves and to allow filtering at a server coupled to the connection oriented network based on more than layer 3 protocol information or virtual LAN identifiers. The present invention is particularly well suited to the IP based systems. For example, in the IP environment, applications differentiate multicasts from one another by registering a particular multicast address on what is called a socket. According to the present invention, information identifying which applications are registered on which sockets is collected and this information is sent to the group address server in the connection oriented network. At the end station one mechanism for doing this is to modify the attach logic of the TCP/IP stack to record every time an application starts or stops registering on a particular socket. An alternative method is to add an intercept layer between applications and the TCP/TP Stack. Another alternative method involves listening to packets at the network driver interface specifications NDIS layer, and determining which multicast addresses are being used by which applications. At the group address server, such as the BUS server, according to the ATM LAN Emulation specification, the multicast address identifiers are listed as a subtable for every end station for each protocol. When a packet is sent to the BUS for multicast distribution, the multicast address of the multicast is checked, and compared against the list maintained for the particular end station. If a match is found, the packet is forwarded to the end station and the process continues to other end stations being managed by the group address server. If the group address of the packet does not match the group address associated with the end station, then that end station is skipped, and bandwidth is saved on the connection oriented network.

Other aspects and advantages of the present invention can be seen upon review of the figures, the detailed description, and the claims which follow. - 9 - Atty Docket No: 15886.870 I:\HOME\MAH\CUENT\15886\870\PATAPPL870 BRIEF DESCRIPTION OF THF. FIGURES Fig. 1 is a block diagram of an ATM network with LAN emulation, which includes management of multiple destination packets according to the present invention.

Fig. 2 illustrates the port configuration table stored in the broadcast and unknown server according to the present invention.

Fig. 3 is a diagram of an end system network protocol stack with a first example of a group address notification process of the present invention.

Fig. 4 is a diagram of an end system network protocol stack with a first example of a group address notification process of the present invention.

Fig. 5 is a flow chart describing the process for forwarding multiple destination packets according to the present invention.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention is provided with reference to Figs. 1 through 5. There are several techniques that can be used to configure a Broadcast and Unknown Server (BUS) in an ATM system, with required group address information according to the present invention. The preferred embodiment described below is optimized for minimizing customer expertise and time for configuration. Alternative methods could be used based on manual configuration of the tables by a network management specialist. Alternatively, end systems could be polled to determine a configuration using standard PING protocols for EP, IPX, XNS, 3Com adapter management protocol (AMP) and other network protocols. In addition, rather than an ATM backbone, the group address server can be utilized in other network architectures with connection oriented or connectionless link layer and physical layer protocols.

An environment of the present invention is illustrated in Fig. 1. In this embodiment, a connection oriented network 10, such as ATM network, is shown. Edge devices 1 1, 12, and 13 are coupled to the ATM network 10. The - 10 - Atty Docket No: 15886.870 I:H'OME\MAH\CUENT\15886\870\PATAPPL.870 edge devices comprise a local area network (LAN) switch and an ATM attachment device, or other network intermediate system as appropriate to the connection oriented network 10 being utilized. A group address server 1 , such as the broadcast and unknown server BUS of the ATM LAN Emulation specification, is included. End systems 15 and 16 are coupled to edge device 1 1. End systems 17 and 18 are coupled to edge device 12. The edge device 12 is also coupled to an extended network 19. End systems 20 and 21 are coupled to edge device 13. In a preferred embodiment of the present invention, the edge devices 1 1, 12, 13 include port status tables which are used to identify the network layer (layer 3) protocols that are in use by end systems coupled to ports on the particular edge devices.

Also, according to the present invention, status information tables 25 are maintained at the group address server 14. Status information according to a preferred embodiment includes for each port on edge devices 1 1, 12, and 13, or alternatively, for each end system accessible through ports on edge devices 1 1, 12, and 13, a multicast group list, and network layer protocol identifiers. Also, according to a preferred embodiment of the present invention, end systems in the overall network, such as end systems 15, 16, 20, 21, include a multicast group notify process which is explained below. Also, end systems in the extended network 19 include multicast notify processes. End systems 17 and 18, as shown in Fig. 1 , represent legacy systems which have not been updated to include the multicast notify processes.

The status information maintained in the tables 25 at the group address server 14 is gathered in response to the multicast notify processes in the end systems, and in response to the port status tables maintained by the edge devices. Status information 25 may also include virtual LAN identifiers and other status information as suites a particular implementation.

Fig. 2 illustrates one organization for the status information tables 25 of Fig. 1. Thus for example, status information tables 25 includes a set of tables, one table 100 for each port W in edge devices 1 1, 12, 13, coupled to network 10 - 1 1 - Atty Docket No: 15886.870 I:\H'OME\MAH\CLIE TM S886\870\PATAPPL.870 which is served by group address server 14. The table for port W is indexed according to layer 3 network protocol identifiers in one embodiment. Thus, for each index, such as index 0 corresponds to a layer 3 network protocol, such as the Internet protocol IP. The entry in the table at index 0 includes the state of the port W that indicates that the corresponding layer 3 protocol is in use, or is not in use by end stations accessible through the port. Next, the entry includes a virtual LAN identifier, and embodiments in which the virtual LAN filtering is also executed. Finally, the entry for index zero includes a multicast group pointer which points to a data structure 101 which includes the multicast group list MAC address tables associated with the particular port W. For a port having a single end system coupled to it, the table 101 will include a list of multicast addresses for which the end system is registered. For port having more than one end system accessible through it, the data structure will include indexing based on the MAC address, or other end system identifier.

As can be seen in Fig. 2, indexes 1 and 2 also include pointers to a multicast group list. Indexes 3 to 255 do not include such pointer, but rather include a no indicator in this field. This corresponds to network protocols for which group address based filtering at the group address server 14 is not executed. In one preferred embodiment, the group address filtering is executed only for the Internet protocol DP based layer 3 networks.

The state of the port maintained in Fig. 2 indicating whether a particular network protocol is in use by end systems accessible through a particular port is maintained in a preferred embodiment according to the techniques illustrated in the above-referenced related application entitled Protocol for Optimized Multicast Services for a Connection Oriented Network Providing LAN Emulation, which is incorporated by reference as if fully set forth herein. The virtual LAN identifier field is populated by manual administration techniques, or other VLAN management processes that suites a particular implementation. The multicast group list data structures 101, 102, 103 are maintained using the multicast notify processes in the end systems, as mentioned above. - 12 - Atty Docket No: 15886.870 I:\HOME\ AH\CLIENT\l 5886\870\PATAPPL.870 Figs. 3 and 4 illustrate alternative implementations of the multicast notify processes implemented in end systems according to the present inventions.

Fig. 3 illustrates a first embodiment of a network interface stack generally 200 in an end system. The stack includes a physical layer 201 which manages connection to a particular physical media or virtual physical layer process.

Above physical layer 201 , a data link layer 202 is executed. Data link layer 202 comprises a process, such as IEEE 802.x protocol, such as Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI) or other process. Above the data link layer 202 is a layer 3 network protocol, such as the IP layer. On top of IP layer 203 sits an application layer 204, such as a hyper text transfer protocol (HTTP), a file transfer protocol (FTP), or a Winsock process which is associated with a network operating system, such as Windows NT. Application layer 204, according to the present invention, includes a multicast registration function 205. A complimentary element of the multicast registration function 206 resides in the IP layer 203. When an application layer process, such as Winsock, decides to listen for a particular group address, the multicast registration function 205 in the application layer 204 executes a registration process which is received by the multicast registration function 206 in the IP layer 203. IP layer 203 is then configured to listen for packets which selected at the data link layer for transfer to the IP layer 203, which include a group address desired by the higher layer functions. According to the present invention, an intercept process 207 resides between application layer 204 and EP layer 203. Intercept process 207 intercepts the registration process, and executes in response to a registration request, a notify multicast server process 208. Notify multicast server process 208 composes a notification packet to be sent to a server on the connection oriented network using the network interface stack. Registration of the group address is completed in IP layer 203 based on the notification protocol, and the application layer process 204 is notified that registration has been successful.

Fig. 4 illustrates an alternative embodiment. As in Fig. 3, a network interface 210 for an end system is illustrated. Network interface 210 includes a - 13 - Attv Docket No: 15886.870 I:\HOME\ AH\CLIENT 5886\870\PATAPPL.870 physical layer 21 1, a data link layer 212, an IP layer 213, and an application layer 214. A multicast registration function 215 in the application layer coordinates with a multicast registration function 216 and a DP layer 213. IP layer 213 according to this embodiment is modified so that it includes a notified multicast process 217. As a element of the multicast registration function 216, the notification protocol is carried out in the Internet layer driver software.

The multicast notification protocol executed in either of the examples of Figs. 3 or Fig. 4 in one example includes a simple acknowledgment-type protocol in which the end system sends a packet to its associated edge device which is identified as a multicast notification packet. This packet is forwarded by the edge device to the group address server. The multicast notification packet carries the data link layer address, such as the MAC address, of the end system in which registration is being accomplished as well as the socket identifier, or other group address identifier.

The edge device appends a port identifier to the notification packet and forwards it to the server. At the server, the status information tables are indexed by the network protocol of the identification packet, and the information in the notification packet is utilized to update the multicast group listing for the identified end station. The server then acknowledges successful update of the status information by sending a packet to the end station. The multicast notification process in the end station receives the acknowledgment, and notifies the application layer process that registration for the group address is complete.

Fig. 5 is a simplified diagram of the multicast management process which is executed in the group address server 14, according to one preferred embodiment.

Thus, the process begins at the server with reception of a multicast frame 300. At this step, a port index i is set to zero. In the next step, the originating port W for the packet, the network layer protocol P, the multicast address of the packet, and the virtual LAN identifier for the packet are all determined, based on information carried in the packet itself After determining this information, an - 14 - Atty Docket No: 15886.870 1. HOME\MAH\CLIENTU S 886\870\P AT APPL.870 iterative process is begun at step 302, where the port index i is incremented. In the next step, port index i is tested to determine whether it is equal to the originating port W (step 303). If it is the originating port, the process branches to block 304 and does not send the multicast to port i. After step 304, the process branches to step 305 where the index i is tested against the number N of ports on edge devices being served by the group address server. If all the ports have been tested as indicated at step 305, then the process is done (step 306). If other ports remain to be tested, then the algorithm loops to step 302 to increment the index i and jumps to step 303 to test for the originating port. If the originating port is not detected at step 303, then the group address server tests whether the protocol P of the packet is enabled for the particular port (step 310). If it is not enabled, then the process branches to step 304. If the protocol is enabled for the port, then the process branches to step 31 1. Also, if the protocol processing on the particular edge device of port i is not enabled, as indicated by a NULL value at this step, then the process likewise branches to step 31 1. At step 31 1, virtual LAN identifier are utilized for filtering the multicast packet. If the virtual LAN identifier does not match for end stations accessible through the port, then the process branches to step 304. If the virtual LAN identifier does match for end systems accessible through the port, or if virtual LAN filtering is not enabled for the particular port, then the process branches to step 3 12. At step 312, a branch is executed based on whether the multicast group registration function is enabled for the particular port. If multicast group registration is not enabled for the particular port, or if a NULL value is encountered in the status information, then the multicast is sent to port i, based on the filtering at steps 310 and 311 (step 313).

If multicast group registration function is enabled for the port and the particular protocol, the process branches to step 314, at which the process determines whether the MC address matches a MC address registered for an end station or end stations on the port. If it does match, the process sends the multicast packet to matching end station(s) accessible through the port (step - 15 - Attv Docket No: 15886.870 I:\HOME M AH\CLIENT\15886\870\PATAPPL.870 313). If it does not match at step 314, then the algorithm branches to step 304, and the packet is not sent on port i. After steps 313 or 304, the process branches to step 305 to continue processing the ports managed by the group address server until all ports have been processed.

According to alternative embodiments of the present invention, the layer 3 protocol filtering and virtual LAN matching steps 310 and 31 1 may not be utilized. Thus, only multicast group registration functions are utilized in this particular implementation. Furthermore, the organization of the status information might be modified to accommodate only multicast group registration. In this embodiment, indexing of the multicast group lists in the group address server 14 is accomplished using end station addresses rather than port numbers in combination with end station addresses. A variety of other organizations for accessing status information might be utilized that suites a particular implementation.

Accordingly, a system for improving the network performance when operating in a LAN emulation environment using asynchronous transfer mode ATM switches has been provided. The BUS server dynamically learns the network protocols and group addresses used by personal computers, network file servers, multicast groups, and/or hosts using the ports of the ATM edge devices. The BUS server then repeats multicast or broadcast messages but only to members of a virtual LAN that are using the protocol identified, and listening for the group address of the packet, and not to those that are not using the protocol, or not listening for the group address. The configuration can be manually set up by network administrators. Also, the present invention provides a technique for automatically configuring the system. This ensures a robust automatically configured system for managing multiple destination packets in a connection oriented network that provides emulation services for connectionless networks.

Although the preferred embodiment described above distributes the learning, monitoring, filtering and transmitting functions between the end - 16 - t Docket No: 15886.870 l:\HOME\MAH\CLIENT 5886\870\PATAPPL870 systems, the edge devices, and the improved BUS server in a manner which efficiently utilizes standard resources in the ATM LAN emulation environment, other configurations of resources could be used. For example, the status table could be maintained in one or more edge devices, or even in an end system on a LAN connected to the edge device. In these examples, muhidestination packets received at the edge device would be processed locally, or sent to the end system executing the server functions across a LAN segment.

The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. It is intended that the scope of the invention be defined by the following claims and their equivalents. - 17 - Atty Docket No: 15886.870 I:\HOME\M AH\CLIENT\15886\870lP AT APPL.870

Claims

CLAIMS What is claimed is:

1. In a connection oriented network which provides emulation of one or more variant network protocols for end systems coupled to edge devices on the connection oriented network, a method for managing transfer of a multiple destination packet having a group address specified at a network layer or above received at incoming ports on edge devices on the connection oriented network, comprising: determining the group addresses for which end systems coupled to the edge devices are listening; identifying the group address carried in a particular multiple destination packet; and transmitting via the connection oriented network the multiple destination packet to end systems listening for multiple destination packets having the identified group address of the multiple destination packet.

2. The method of claim 1, including establishing a list of group addresses for end systems accessible through edge devices on the connection oriented network.

3. The method of claim 2, including a step on end systems coupled to the edge devices, comprising sending to a server for the connection oriented network notice of group addresses for which the end systems are listening, and maintaining the list of group addresses in response to the notice in the server.

4. The method of claim 2, wherein the end systems include a protocol stack, and including detecting registration in the protocol stack at the network layer that a function in the end system processes packets having a particular group address, and in response to the detection, sending a notice - 18 - Attv Docket No: 15886.870 1'.\HOME\MAH\CL1ENTV15886\870\PATAPPL.870 indicating the panicular group address from the end system to a server for the connection oriented network, and maintaining the list of group addresses in response to the notice.

5. The method of claim 1 , wherein the group address comprises an Internet protocol EP address.

6. The method of claim 1 , wherein the group address comprises a transport control protocol TCP socket identifier over an Internet protocol EP address.

7. The method of claim 1, including: determining a network protocols not in use on end systems coupled to ports of the edge devices, transmitting via the connection oriented network the multiple destination packet to ports of edge devices other than ports for which the determined network protocol is not in use by systems accessible through the port; and storing a status table of status information for the ports on edge devices on the connection oriented network indicating protocols in use by systems accessible through the respective ports.

8. The method of claim 7, including indexing the list of group addresses in the server based on protocol identifiers.

9. The method of claim 1, including: learning at the edge devices which network protocols are not in use by systems coupled to the ports of the edge devices. - 19 - Attv Docket No: 15886.870 I:'HOME\MAH\CLIENTM 5886\870\PATAPPU870

10. The method of claim 1, including: sending via the connection oriented network the multiple destination packet from an edge device which receives the multiple destination packet at an incoming port to a server on the connection oriented network; and executing said step of determining and said step of transmitting at the server.

11. 1 1. The method of claim 7, wherein there are a plurality of emulated networks using one or more network protocols, and the status information for the respective ports includes an indication associating an emulated network with the respective ports, and including determining the emulated network for which the multiple destination packet is intended, and transmitting the multiple destination packet only to ports associated with the determined emulated network.

12. In a connection oriented network which provides emulation of one or more variant network protocols for end systems accessible through ports of edge devices on the connection oriented network, a method for managing transfer of multiple destination packets received at edge devices on the connection oriented network, comprising: reporting to a server for the connection oriented network the group addresses in use by end systems accessible through the edge devices; storing at the server, in response to the step of reporting, status information for end systems accessible through edge devices on the connection oriented network, including an indication of group addresses in use by the end systems; sending via the connection oriented network the multiple destination packet from an edge device which receives the multiple destination packet at an incoming port to the server for the connection oriented network; - 20 - Attv Docket No: 15886.870 I:\HOME\M AHCLIENTUJ886\870\PATAPPL.870 15 determining at the server the group address of the multiple destination 16 packet; and ^ 17 transmitting from the server via the connection oriented network the 18 multiple destination packet to end systems for which the status information 1 indicates that the determined group address is in use. 1

13. The method of claim 12, wherein the step of storing includes: 2 providing a status table of the status information for the ports on edge 3 devices on the connection oriented network, and indexing the status table in the 4 server based on protocol identifiers. 1

14. The method of claim 12, wherein there are a plurality of emulated 2 networks using one or more network protocols, and the status information for 3 the respective ports includes an indication associating an emulated network with 4 the respective ports, and including determining the emulated network for which 5 the multiple destination packet is intended, and transmitting the multiple 6 destination packet only to ports associated with the determined emulated 7 network. 1

15. The method of claim 12, wherein the one or more variant 2 network protocols includes a connectionless network protocol. 1

16. The method of claim 12, wherein the one or more variant 2 network protocols includes a carrier sense multiple access network protocol. 1

17. The method of claim 12, wherein the one or more variant 2 network protocols includes a token passing ring network protocol. 1

18. The method of claim 12, wherein the connection oriented 2 network comprises an asynchronous transfer mode (ATM) network. - 21 - Atty Docket No: 15886.870 I:\HOME\MAH\CUENT\l 5886\870\PATAPPL870 1

19. In an end system connected to a network to receive and transmit ^ 2 at least one of real and virtual physical layer network packets, a network 3 interface comprising: 4 a data link layer process executed in the end system which filters physical 5 network packets for reception at the end system; 6 a network layer process executed in the end system, and coupled with the 7 data link layer process, which filters the received physical layer packets at a 8 network layer to select network layer packets for processing by the end system; 9 an application layer process executed in the end system, and coupled with 10 the network layer process, which processes the selected network layer packets; 1 1 a registration process in the end system to register a network layer group 12 address with the network layer process to enable selection of network layer 13 packets having the network layer group address in the network layer process; 14 and 15 resources coupled with the registration process to notify a server coupled 16 with the network that the network layer group address is registered with the 17 network layer in the end system. 1

20. The network interface of claim 19, wherein the registration 2 process comprises an element of the application layer process. 1

21. The network interface of claim 19, wherein the resources coupled 2 with the registration process to notify a server, include an intercept process 3 between the network layer process and the registration process. 1

22. The network interface of claim 19, wherein the resources coupled 2 with the registration process to notify a server, include an element of the 3 network layer process. - 22 - Atty Docket No: 15886.870 I:\HOME\ AH\CUENT\l 5886\870\PATAPPL.87O

23. The network interface of claim 19, wherein the network layer process comprises an Internet protocol EP driver.

24. The network interface of claim 23, wherein the data link layer process comprises an Ethernet driver.

25. The network interface of claim 23, wherein the data link layer process comprises an Token Ring driver.

26. The network interface of claim 23, wherein the data link layer process comprises an Fiber Distributed Data Interface driver.

27. The network interface of claim 23, wherein the data link layer process comprises a driver for a connectionless data link layer protocol.

28. The network interface of claim 19, wherein the wherein the resources coupled with the registration process to notify a server, include a process to send a notification packet to an agent for the server.

29. A method according to any of claims 1-18 substantially as described hereinabove or illustrated in any of the drawings.

30. A network interface according to any of claims 19-28 substantially as described hereinabove or illustrated in any of the drawings. For the Applicant Advocates, Patent Attorneys & Notaries P-1703-IL - 24 -