Stackable ring network including burst transmission of data packet

• US 6,684,258 B1
• Filed: 04/12/2000
• Issued: 01/27/2004
• Est. Priority Date: 12/23/1999
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Stapleton, Nicholas M, Creedon, Tadhg, Quinlan, Una, Gavin, Vincent, De Paor, Denise
• Primary Examiner(s): Lin, Wen-Tai
• Application Number:
  US09/547,759
• Time in Patent Office: 1,385 Days
• Field of Search: 709/208-211, 709/251, 370/455, 370/424, 370/456, 370/452, 370/223
• US Class Current: 709/251
• CPC Class Codes: H04L 12/433 with asynchronous transmission, e.g. token ring, register insertion

Abstract

A stackable network unit which can form a ring with other units has a master mode in which it can place packets on the ring, so that they can be ultimately forwarded from other units, and a repeat mode in which it can make a request for transfer of mastership of the ring, inserting bits in a header of an arbitration packet. If a master unit has completed the transmission of a packet and, preferably, after the required inter-packet gap has elapsed, it has not yet received an arbitration header to permit the making of an arbitration decision it can transmit a subsequent packet. The header information of this packet indicates to the other units that this subsequent packet is part of a burst of packets and the other units should not set requests in the header of this packet because this packet would not be used for arbitration. The master unit indicates the nature of the subsequent packet by setting a sequence number in the header of the packet to distinguish it and following packets in a burst from the ‘first’ packet which is the one used to pick up requests from the units that may need to become the master unit.

Claims

1. A network unit for sending and receiving data packets and connectable in a ring with other similar units, the network unit having:

a master mode, wherein it can place packets on the ring and arbitrate in response to requests for mastership in packets received from the ring to determine whether to retain or relinquish mastership; and

a repeat mode, wherein the network unit can forward on the ring packets received by way of the ring but is not permitted to place packets on the ring, and wherein the network unit is permitted to insert a request for transfer of mastership in a packet and in response to a packet denoting a transfer of mastership to the network unit to change from the repeat mode to the master mode;

wherein the network unit in said master mode is operative to send, after an arbitration packet into which a request for transfer of mastership can be inserted by another unit, and before said arbitration packet returns to said network unit by way of said ring, at least one further data packet and said at least one further data packet has a header which prevents other units from inserting said requests for transfer of the mastership of the ring.

2. A network unit according to claim 1 wherein said network unit causes said further data packet to indicate a sequence number.

3. A network unit for sending and receiving data packets and connectable in a ring with other similar units, the network unit having:

a master mode, wherein it can place packets on the ring and arbitrate in response to requests for mastership in packets received from the ring to determine whether to retain or relinquish mastership; and

a repeat mode, wherein the network unit can forward on the ring packets received by way of the ring but is not permitted to place packets on the ring, and wherein the network unit is permitted to insert a request for transfer of mastership in a packet and in response to a packet denoting a transfer of mastership to the network unit to change from the repeat mode to the master mode;

wherein the network unit in said master mode is operative to send, after an arbitration packet into which a request for transfer of mastership can be inserted by another unit, and before said arbitration packet returns to said network unit by way of said ring, at least one further data packet;

wherein the operation of the unit is controlled by a state machine which includes, when the network unit is in the master mode;

a first state in which the network unit is waiting for data;

a second state wherein the network unit is placing packets on the ring;

a third state in which the network unit provides an inter-packet gap; and

a fourth state in which the network unit is arbitrating whether to retain or relinquish mastership of the ring;

wherein the state machine may transition from the third state to the fourth state when said arbitration packet is received and may transition from the third state to the first state in the absence of reception of said arbitration packet in order to send said at least one further data packet onto the ring.

4. A network unit according to claim 3 wherein packets placed by the network unit on the ring during said master mode include a header which includes a first field and a second field, said header can convey a request for mastership of the ring when said first and second fields have respective first predetermined values, and said header indicates a sequence number of packets in a burst when the first field has its first respective predetermined value and the second field has a value other than its said first predetermined value.

5. A network unit according to claim 4 wherein said header denotes a transfer of mastership when said first field in the header has a second predetermined value.