High speed linking module

Details High speed linking module High speed linking module

1999-10-28

2001-02-13

Hsu, Alpus H. (Department: 2738)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

C370S539000, C341S101000, C709S241000

Reexamination Certificate

active

06188702

ABSTRACT:

TECHNICAL FIELD
The present invention relates, in general, to an apparatus and method for linking data processors and peripheral devices and, more specifically, to an apparatus and method for linking devices over high speed fiber optic links.
BACKGROUND OF THE INVENTION
Data centers are typically linked together so that data may be shared by multiple customers, who are remotely located from each other. The customers, such as banks and credit card issuers, need high speed connectivity between their server systems and mainframe systems to provide quality service and maximize their investment in information management. Applications that require such high speed connectivity include transaction co-processing, massive file transfers for decision support, archival databases for disaster recovery and transaction reporting requirements.
Referring to
FIG. 1
, there is provided a data processing interconnection system
10
of the prior art. An example of system
10
is an IBM data processing interconnection system known as Enterprise Systems Connection (“ESCON”) (Trade Mark). “ESCON” is an interconnection system using fiber optic technology. Fiber optic links, such as links
14
,
18
,
22
and
26
create a local area network extending for kilometers among numerous systems, such as host processor
12
, control units
24
and
28
.
In “ESCON” architecture multiple systems may communicate with each other via channel-to-channel communications. For example, multiple mainframe systems may communicate channel-to-channel or gain access to multiple devices or communication control units. Referring to
FIG. 1
, channel directors
16
and
20
are capable of employing any-to-any, point-to-point switching and may make numerous physical connections between each other and peripheral devices. As shown, channel director
20
connects four fiber optic links
18
from channel director
16
with two fiber optic links
22
and two fiber optic links
26
, each respectively branching to control units
24
and
28
.
Although not shown in
FIG. 1
, channel director
20
or
22
may have as many as 256 optical ports to support as many as 128 “ESCON” connections simultaneously and without contention. Each channel director includes a set of quad port adapters (QPAs). Each QPA handles the “ESCON” input or output data with four individual ports. The ports include either multi-mode optical transceivers or single-mode optical transceivers. Two QPA modules are shown in
FIG. 1
, namely QPA module
17
and QPA module
19
.
A more detailed arrangement of QPAs is shown in FIG.
2
. As illustrated, multiple QPAs
17
a
-
17
n
are coupled to switch matrix
15
within channel director
16
. Each QPA has four output/input ports (
27
a
-
27
n
) for providing up to four connections to remote devices. Switch matrix
15
provides the switching fabric to connect any one ESCON port to any other ESCON port. For example, two ports (
27
a
) in QPA (1) are connected to two ports (
27
b
) in QPA (2). In this manner, channel director
16
provides multiple interfaces and channel-to-channel switching among multiple devices.
A physical link between two points may consist of two fibers, one for transmitting and one for receiving. Information on the link is transmitted in a special 10-bit code, giving an instantaneous link rate of 20 megabytes per second or 200 megabits per second. After deducting for control (e.g., pacing bytes) and data encoding overhead, a channel data rate for real application data of 17 megabytes per second is achieved.
Data are transmitted in the form of packets of characters called frames. Each character contains 10 bits when use is made of the 8 of 10 code to provide a dc balanced code. The frames can vary in size from 12 bytes to 1036 bytes. Each frame includes both the frame source address and its destination address. The addresses are used to route frames through the network. A switch matrix controller (not shown) within the channel director examines the destination address and dynamically connects the port receiving the frame to the destination port.
“ESCON” technology permits a maximum link rate of 200 megabits/sec between channel directors. The physical links are one-to-one and one port is required at each channel director to support both sides of the link. This one-to-one arrangement can become expensive, because valuable ports and fiber are consumed to support communications between channel directors. Typically, a user must lease one fiber optic link for every port in a control unit. More detail of “ESCON” architecture is provided by S. A. Calta, et al. in “Enterprise Systems Connection (ESCON) Architecture-System Overview”, July 1992, (IBM Journal Res. Development, Vol. 36, No. 4) and is incorporated herein by reference.
A need still exists for an apparatus and method for communicating between channel directors that does not require a one-to-one physical link per port. A need also exists for an interface device that may simultaneously support connectivity from multiple “ESCON” ports onto a single fiber link to reduce the cost of leasing fiber links.
SUMMARY OF THE INVENTION
To meet this and other needs, and in view of its purposes, the present invention provides an apparatus and a method for communicating between two devices over a single link, wherein each device has a plurality of ports. The method includes:
(a) converting a plurality of data streams from respective ports of a first of the two devices into one serial data stream, including the steps of:
(i) multiplexing at least two of the plurality of data streams into a first intermediate output stream;
(ii) multiplexing at least two other of the plurality of data streams into a second intermediate output stream;
(iii) serializing the first and second intermediate output streams into the serial data stream,
(iv) synchronizing the serialization of the first and second intermediate output streams,
(v) tagging output data in the serial data stream as corresponding to data from each of the respective ports of the first device, and
(vi) transmitting the serial data stream on the single link to a second of the two devices;
(b) converting the serial data stream in the second device to at least four input data streams, and
(c) sending each of the input data streams to a port of the second device.
Step (b) includes the steps of:
(i) de-serializing the serial data stream into first and second intermediate parallel data streams,
(ii) demultiplexing the first intermediate parallel data stream into two parallel data streams on two respective data lines;
(iii) demultiplexing the second intermediate parallel data stream into two other parallel data streams on two other respective data lines;
(iv) synchronizing the de-serialization of the first and second intermediate output streams and
(v) separating data in the serial data stream to data for each of the respective data lines.
In one embodiment, the single link is a fiber optic link. Also included is a signal having a cycle with a first phase and a second phase, and tagging two of the respective ports with the first phase and tagging two other respective ports with the second phase.
It is understood that the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.


REFERENCES:
patent: 3872257 (1975-03-01), Bleickardt et al.
patent: 4646286 (1987-02-01), Reid et al.
patent: 5001711 (1991-03-01), Obana et al.
patent: 5414851 (1995-05-01), Brice, Jr. et al.
patent: 5757297 (1998-05-01), Ferraiolo et al.
Enterprise Systems Architecture/390—ESCON I/O Interface, Chapter 1, General Concepts SA22-7202-02 21 pages (1992).

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