Method for assigning priority to traffic between local area networks interconnected via a backbone network

Claim 1

A method for assigning priority to traffic between local area networks which are interconnected to one another via a backbone network, over respective transmission lines, wherein data is transmitted from one local network to another in a succession of varied-length frames, each having a source address and a destination address, and data buffering is required in the backbone network at a point where data is to be transmitted over a respective transmission line which has a lower transmission capacity than does said backbone network, said method comprising: (a) determining at said point the length of each respective frame which is about to be received by the backbone network from each respective local area network, with a predetermined accuracy as to whether said length is at least as along as, or is shorter than a given length, and thus, obtaining frames of at least two different frame-length categories, each at least tentatively having a respective, different frame-priority status, of which at least one is lower than another and at least one is higher than another; (b) causing each frame having a length which is longer than said given length to have a marking identifying that frame as a lower priority frame and sending that frame into a respective queue for lower priority frames to be transmitted along a respective said transmission line into said backbone network for transmission along another respective said transmission line into another said local area network; (c) comparing at least one address of a pair of addresses formed by the source and destination address of each respective about to be received frame, with the corresponding at least one address of each frame which remains in, or has been in the respective queue for lower priority frames within a time interval of given length ending at the present, and (i) upon finding correspondence in said at least one address, sending the respective about to be received frame into said respective queue for lower priority frames, but (ii) upon finding a lack of correspondence in said at least one address, causing the respective about to be received frame to have a marking identifying that frame as a higher priority frame, and sending that frame into a respective queue for higher priority frames to be transmitted along a respective said transmission line into said backbone network for transmission along another respective transmission line into another said local area network; and (d) checking on priority of successive leading frames waiting in said queues and forwarding said leading frames from respective said queues into said backbone network based on such checking, giving precedence to leading frames having higher priority over those having lower priority.

Claim 2

A method for assigning priority to traffic between local area networks which are interconnected to one another via a backbone network, over respective transmission lines, wherein data is transmitted from one local network to another in a succession of varied-length frames, each having a source address and a destination address, and data buffering is required in the backbone network at a point where data is to be transmitted over a respective transmission line which has a lower transmission capacity than does said backbone network, said method comprising: (a) determining at said point the length of each respective frame which is about to be received by the backbone network from each respective local area network, with a predetermined accuracy as to whether said length is at least as along as, or is shorter than a given length, and thus, obtaining frames of at least two different frame-length categories, each at least tentatively having a respective, different frame-priority status, of which at least one is lower than another and at least one is higher than another; (b) causing each frame having a length which is longer than said given length to have a marking identifying that frame as a lower priority frame and sending that frame into a respective queue for lower priority frames to be transmitted along a respective said transmission line into said backbone network for transmission along another respective said transmission line into another said local area network; (c) comparing at least one address of a pair of addresses formed by the source and destination address of each respective about to be received frame, with the corresponding at least one address of each frame which remains in, or has been in the respective queue for lower priority frames within a time interval of given length ending at the present, and (i) upon finding correspondence in said at least one address, sending the respective about to be received frame into said respective queue for lower priority frames, but (ii) upon finding a lack of correspondence in said at least one address, causing the respective about to be received frame to have a marking identifying that frame as a higher priority frame, and sending that frame into a respective queue for higher priority frames to be transmitted along a respective said transmission line into said backbone network for transmission along another respective transmission line into another said local area network; and (d) checking on priority of successive leading frames waiting in said queues and forwarding said leading frames from respective said queues into said backbone network based on such checking, giving precedence to leading frames having higher priority over those having lower priority.