TELECOMMUNICATIONS SWITCH WITH MULTIPLE PORTS FOR HOST-NODE COMMUNICATIONS

Abstract: The system includes switching nodes with multiple ports for node-host communication, each port thereby connects the switching nodes to one or more hosts. One of the ports in a switching node is designated as a primary or master port and it connects the switching node to a default host. The default host controls all ports in the switching node and because applications on the default port are given the highest priority during switching node processing, the default host is useful for applications that require instant response from the switch. The other ports in the switching node are secondary ports and they connect the switching node to one or more secondary hosts simultaneously. The applications on the secondary hosts are given a lower priority than the default host's application. Therefore, the secondary hosts are useful for applications that do not require instant response from the switching nodes.

Description: TELECOMMUNICATIONS SWITCH WITH MULTIPLE PORTS FOR HOST-NODE COMMUNICATIONS TECHNICAL FIELD This invention relates to telecommunications switching systems and specifically to a system in which each of the switching nodes has multiple ports for node-host communications. BACKGROUND OF THE INVENTION An example of the switching system to which the present invention applies is described in U.S. Patent No. 5,544,163, Expandable Telecommunications System, the contents of which are incorporated herein by reference. The switching system comprises a plurality of programmable switching nodes and a host that exercises supervisory control over the switching nodes. The host is typically implemented as a personal computer on which host software applications run to provide various supervisory functions. The switching nodes are interconnected by an internodal switching network. A second net- work termed the "host network," interconnects the switching nodes and the host for supervisory communications. Examples of the host supervisory applications include call setup and teardown applications and applications that perform various system monitoring and administrative functions. In the above-referenced patent, a single system host communicates with the switching nodes and all messages from the switching nodes are sent to that host. However, in some environments the host may be overloaded, for example, by a high frequency of call setup and teardown operations and by other functions that may be assigned by the system operator. Moreover various nodes or groups of nodes may be situated in widely separated geographic locations and communications between a single host and all of the switching nodes may be substantially more expensive than distribution of the host functions on a geographic basis. To solve these problems, a prior system divides the supervisory applications among multiple hosts. This takes care of the host overload problem as well as the -2- problem with widely separated geographic locations. However, the supervisory applications usually have different processing priorities, with applications that perform call setup and teardown functions requiring the highest priority in the switching node. The operators of the switching system may divide the supervisory host applications among multiple hosts based on the their priorities. For example, the operator may limit to one host supervisory applications that control and configure various switching node features or perform call setup and teardown functions. The lower priority supervisory applications will then be placed on other hosts. However, all messages received by the switching nodes have the same priority and since all hosts communicate with the switching nodes, the switching nodes in turn, process lower priority applications at the same priority level as higher priority applications. This is not a problem with a single host system since a single host can control the priority levels by sending requests to the nodes according to the priority levels of the requests. SUMMARY OF THE INVENTION In accordance with the invention, each switching node in the system has multiple ports for node-host communications, both ports being connected to the host network. One of the ports in each switching node is designated as a primary or master port and it is used exclusively for communications with a primary host. Incoming messages on the master port are given the highest priority on the switching node and, the primary host is therefore preferred for applications that require high priority responses in the switching nodes. The other ports in the switching nodes are secondary ports and they are used for communications with one or more secondary hosts. Since incoming messages on the secondary ports have a lower priority, the secondary hosts are preferred for applications that perform query operations, switch monitoring and other applications that do not require high priority response in the switching nodes. The switching nodes process incoming messages at the primary ports with a higher priority than those arriving at the secondary ports. This automatically provides higher priority handling to higher priority tasks. Although incoming messages on the master port have higher priorities than in- coming messages on the secondary ports, the fairness algorithms often used in priority arrangements do not process higher priority tasks to the complete exclusion of lower priority tasks. A switching node may therefore be overloaded in some situations and fail to respond to higher priority applications as speedily as required. Therefore, we prefer to provide the primary host with overall control of communications with the switching nodes, including those that are transmitted to the secondary ports. Specifically, the primary host can disable port communications at any of the switching nodes. This terminates host-node communications with the designated ports. It thus ensures that the affected node can catch up with time-critical tasks, such as call setup, that have fallen behind. The primary host can later re-enable the affected port when the switching node has sufficiently reduced its backlog of high-priority tasks. BRIEF DESCRIPTION OF THE DRAWINGS The invention description below refers to the accompanying drawings, of which: Fig. 1 is a fragmentary diagram of a switching system to which the present invention may be applied; and Fig. 2 is a diagram of a multiple-host/switching node configuration in accordance with the present invention. DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT As shown in Fig. 1, a typical switching system to which the invention applies comprises a plurality of switching nodes 6b-6e connected by a ring-like internodal switching network 12. Each of the switching nodes is associated with a plurality of network/line interfaces which provide connections between the switching system and subscribers' lines, for example, and also with other switching systems such as the PSTN. Overall supervision, i.e. control and monitoring of the switching functions of the network 12, is provided by supervisory applications on host computers (hosts) 4a-4e that are linked to the switching nodes 6b-6e by a host network 8 which, in the illustrated example, is an Ethernet network. The supervisory applications are divided among multiple hosts 4a-4e. In accordance with the present invention, each switching node 6b-6e has multiple host ports that connect to the host network 8. -4- Each switching node may have one or more network ports. As shown in Fig. 2, in the preferred embodiment of the invention, each switching node 6b-6e has five host network ports 30a-30e. The primary port 30a in each switching node 6b-6e is used exclusively for communications between the switching node and a primary host 4a. The secondary ports 30b-30e in each switching node is used for communications between the switching node and one or more secondary hosts 4b-4e. All of the applications on the hosts 4a-4e establish virtual connections 40a-40e with the applications on the switching nodes 6b-6e over the host network 8. These connections are preferably TCP socket connections. Incoming messages on the primary port 30a receive the highest priority in each switching node. Thus, the primary host 4a is preferred for supervisory applications that require high priority responses from the switching nodes 6b-6e. When the system starts up, the primary and secondary hosts 4a-4e register with the switching nodes. Thereafter a registration software module 50 in each switching node configures the primary port 30a for exclusive communication with the registering primary host 4a and it configures the secondary ports 30b-30e to communicate with all other hosts 4b-4e that register with the switching node. All communications between the switching nodes and the secondary hosts 4b-4e then pass through secondary ports 30b-30e and all communication between the switching nodes and primary host 4a pass through the primary port 30a. Thus after startup, if a secondary host 4b-4e tries to communicate with the switching node through the primary port 30a, the switching node rejects the incoming message and returns an error message to the originating host. Also if a secondary host 4b-4e tries to initiate a switching node task that is exclusively controlled by the primary host 4a, the switching nodes returns an error message. More specifically, when the system starts up, the primary host 4a may broadcast over the host network its status as primary host. The secondary hosts 4b-4e also broadcast their status to the nodes. The switching nodes 6b-6e broadcast their primary and secondary port addresses to all host. The secondary hosts 4b-4e store the secondary port addresses in their address tables 70 and they ignore the primary port addresses. The primary host 4a also stores the primary ports addresses in its address table 70 and it ignores the secondary port addresses. Thus, the secondary hosts 4b-4e communicate with the switching nodes 6b-6e exclusively through the secondary ports 30b-30e and the primary host 4a communicates exclusively through the primary ports 30a. Thereafter, each host 4a-4e registers with the switching nodes 6b-6e by sending messages to the switching nodes 6b-6e over the host network 8. The registration mes- sages inform the switching nodes 6b-6e of the types of switch-initiated messages that should be routed to that host. The registration messages are stored in registration tables 60 in each of the switching nodes 6b-6e and are preferably battery backed-up for protection against a switching node reset. Multiple hosts 4a-4e may register for the same switch-initiated message. In some situations, the switching node may be overloaded and fail to respond to higher priority applications as speedily as required. Therefore, the system operator uses the primary host 4a to exercise overall control over host-node communications. More specifically, the primary host 4a can disable port communications at any of the switching nodes. This terminates host-node communications with the designated ports and it en- sures that the affected node can catch up with time critical tasks that have fallen behind. The primary port 4a may later enable the affected port when the switching node has sufficiently reduced its backlog of high priority tasks. In addition to controlling the ports, the primary host 4a also exclusively controls the way each switching node 6b-6e responds to polls about its current state. Instead of immediately responding to each poll message, the primary host 4a instructs the switching nodes 6b-6e to broadcast poll messages at predetermined intervals to the all hosts 4a-4e. In addition to supervisory applications, the primary host 4a processes all switch- initiated messages that cannot be sent to any secondary hosts 4b-4e. This occurs when the secondary hosts 4b-4e do not register for a specific switch-initiated message or when the secondary host 4b-4e that registered for the message is down or has a disabled host- node communication. During message processing, the switching nodes 6b-6e queue host-initiated messages for each message type. The switching nodes 6b-6e process each host-initiated message and match the result with the appropriate queued message in order to deter- mine which host is the originating host. The switching nodes 6b-6e return errors if a host 4a-4e tries to send more messages when the switching nodes 6b-6e message queues -6- are full. If a host-initiated message requires multiple responses from a switching node, the switching nodes process each response one at a time. Only one host 4a-4e at a time can send a host-initiated message that requires multiple response from the switching nodes 6b-6e. It will be apparent that the invention provides for highly flexible control of a switching network, that is, it facilitates configuration and modification of the supervisory function by the system operator. Specifically, it facilitates adaptation of this supervisory configuration according to network traffic, geographic locations and other relevant factors.

Claims: -7- CLAIMS 1 1. A communications network comprising: 2 A) a plurality of switching nodes each of which provides connections be- 3 tween the communications network and subscriber lines or other switch- 4 ing networks; s B) an internal network interconnecting the switching nodes for conveying 6 switched telecommunications data between them; 7 C) a primary host computer and at least one secondary host computer that 8 run supervisory host applications with different priorities, the host appli- 9 cations exercising supervisory control over the nodes, and the primary o host computer running a host application with higher priority than the i host applications on the secondary hosts; 2 D) a host network linking each host computer with the switching nodes; 3 E) each node having a primary port and at least one secondary port for 4 communications with the host computers connected to the host network; s F) means in each switching node for assigning higher priority to incoming 6 messages received on the primary port than the messages received on the 7 secondary port; and s G) means for restricting the primary ports to communications between the 9 switching nodes and the primary host. i 2. The communications network of claim 1 including port control means in each 2 node for responding to port-control messages received by the primary port of that node, 3 said control means disabling and/or enabling communications through the secondary 4 port. i 3. The communications network of claim 2 wherein the primary host comprises 2 means for exercising overall control over communications between the primary and sec- 3 ondary hosts and the switching node. -8- 4. The communications network of claim 3 further comprising: A. means for registering the primary and secondary hosts with the switching nodes after the system starts up; B. means for configuring the primary port through a primary port driver for ex- elusive communication with the primary host; and C. means for configuring the secondary port through a secondary port driver for communication with the secondary host. 5. The communications network of claim 4 wherein the registration messages from the hosts are stored in registration tables in each node and said registration messages inform the node of the type of switch-initiated messages that each host processes. 6. The communications network of claim 5 wherein the primary host further com- prises means for processing all switch-initiated messages that cannot be sent to secon- dary host. 7. The communications network of claim 6 wherein each switching node queues incoming host-initated messages and matches results with the queued messages in order to determine the originating host. 8. The communications network of claim 7 wherein the primary host further com- prises means for exercising exclusive control over the way each node responds to host- initiated polls about the state of that node. 9. The communications network of claim 8 wherein each switching node returns error messages to hosts sending host-initated messages when its message queue is full. 10. A method of processing incoming messages in a communications network, said network having at least one switching node connected by a host network to a primary host computer and to at least one secondary host computer, each host computer having software applications with different priorities that exercise supervisory control over the -9- nodes, each node having a primary port and at least one secondary port for communica- tions with the host computers, said method comprising the steps of: assigning a higher processing priority in each node to incoming messages re- ceived on the primary port; assigning a lower processing priority in each node to incoming messages re- ceived on the secondary port; restricting the primary ports to communications with the primary host; and processing incoming messages received on the primary port at a higher priority level than those received on the secondary port. 11. The method of claim 10 wherein the primary host exercises overall control over communications between the primary and secondary hosts and the switching node by the steps of: A. disabling port communications with hosts connected to an affected port; and B. re-enabling port communications with hosts connected to the affected port. 12. The method of claim 11 further comprising the steps of: A. registering the primary and secondary hosts with the switching nodes after the system starts up; B. storing registration messages from the hosts to the node in registration ta- bles; C. using the registration messages to inform the node of the types of switch- initiated messages that each host processes; D. configuring the primary port through a primary port driver for exclusive communication with the primary host; E. configuring the secondary port through a secondary port driver for commu- nication with the secondary host; and -10- F. queuing incoming host-initated messages, processing each message in the queue and matching results with the queued messages in order to determine the originating host. 13. The method of claim 12 further comprising the step of processing in the primary host all switch-initiated messages that cannot be sent to secondary host. 14. The method claim 13 for exercising exclusive control over the way each node responds to host-initiated polls about the state of that node by the step of sending port- control messages from the primary host to each node

Inventors: GHAI RAJAT, HIGGINS PETER, GHAI, RAJAT, HIGGINS, PETER
Applicants: EXCEL SWITCHING CORP, EXCEL SWITCHING CORPORATION
Application year: 1999
Main classification: H04Q3
IPC codes: G06F13, H04M3, H04Q3