CONCURRENT RESOURCE REQUEST RESOLUTION MECHANISM
 Inventor: Bruce R. Zelle, Naperville, 111.
 Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories,
Murray Hill, N.J.
[21} Appl. No.: 175,695
 Filed: Mar. 31,1988
 Int. C1.5 H04L 5/00
 U.S. CI 370/85.15; 340/825.5;
 Field of Search 370/60, 86, 89, 110.1,
370/85; 340/825.05, 825.5
 References Cited
U.S. PATENT DOCUMENTS
4,524,440 6/1985 Orsic 370/54
4,536,873 8/1985 Leete 370/86
4,612,635 9/1986 Leete 370/89
4,761,780 8/1988 Bingham et al 370/60
4,780,870 10/1988 McHarg et al 370/60
4,797,880 1/1989 Bussey, Jr. et al 370/60
Primary Examiner—Douglas W. Olms
Assistant Examiner—Melvin Marcelo
Attorney, Agent, or Firm—Werner Ulrich
A high capacity metropolitan area network (MAN) is described. Data traffic from users is connected to data concentrators at the edge of the network, and is transmitted over fiber optic data links to a hub where the data is switched. The hub includes a plurality of data
switching modules, each having a control means, and each connected to a distributed control space division switch. Advantageously, the data switching modules, whose inputs are connected to the concentrators, perform all checking and routing functions, while the 1024X 1024 maximum size space division switch, whose outputs are connected to the concentrators, provides a large fan-out distribution network for reaching many concentrators from each data switching module. The data switching modules chain groups of incoming packets destined for a common outlet of the space division switch so that only one connection in that switch is required for transmitting each group of chained packets from a data switching module to a concentrator. MAN provides security features including a port identification supplied by the data concentrators, and a check that each packet is from an authorized source user, transmitting on a port associated with that user, to an authorized destination user that is in the same group (virtual network) as the source user.
In accordance with one enbodiment of the invention, a data ring communicates space division switch outlet availability to each of the data switching modules in turn, in order to resolve the contention among these modules for a particular outlet. Each data switching module maintains a list of outlets for which it has accumulated a group of at least one packet destined for that outlet; a data switching module then seizes an available outlet by marking that outlet unavailable in the data communicated by the data ring.