Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
1998-09-28
2002-07-16
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Fault recovery
Bypass an inoperative station
C370S228000, C370S404000, C709S241000
Reexamination Certificate
active
06421317
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to data processing in a multi-users communication network and more particularly to a Token Ring Automatic Load Balancing/Backup function in a multiple users environment.
BACKGROUND ART
The invention refers to Fe following terminology:
802.2 TEST frame: is an 802.2 Data Link Control (DLC) frame which is used for discovering a route toward a remote station.
XID frame: is an 802.2 DLC frame which is used for exchanging identification before establishing a connection.
SABME (Set Asynchronous Balanced Mode Extended) Frame: is an 802.2 DLC frame which is used for establishing a connection.
UA (Unnumbered Acknowledgment) Frame: is an 8022 DLC frame which is used for confirming a connection establishment.
Routing Information: is an 802.5 MAC Frame field containing the route which is used for a connection (list of ring numbers and bridge numbers).
Token Ring User: is the host computer that is shared and connected to a plurality of Token Ring stations.
MAC address: is the station address on the Token Ring.
Load Balancing function: enables to switch to another route when a route is overloaded.
Backup function: enables to back up a route which has become inoperative.
Resolve Procedure: enables to discover the route to the destination station by means of the Test frame.
SAP: Service Access Point used for identifying a user of the DLC 802.2. All Route Broadcast implement& the broadcast function that is used for copying the Test frame on all the rings.
The Automatic Load Balancing/Backup function is an improvement of the Token Ring Architecture. It allows an automatic balancing of the traffic between different Token Ring Adapters using the same MAC address, and also automatic backup in case one of the Token Ring adapter becomes unavailable.
The U.S. Pat. No. 5,493,689 describes a system for configuring an event driven interface including control blocks defining good loop locations in a memory which represent detection of a characteristic pattern. This technique is a combination of a source of control vectors which sends control vectors in a programmable performance vector generator which is coupled to a data communications network to be monitored and controlled. This invention enables real-time load distribution, load balancing, problem determination, routing and customer services, but it is to be implemented in environment that uses an expert system which analyzes the event vectors and provides monitoring information and control signals to the network.
The U.S. Pat. No. 5,606,693 and 5,668,986 which respectively relate to “A distributed database management over a network” and to “A method and apparatus for handling data storage requests in a distributed data base environment” are dedicated to a distributed database application for logging large volumes of data to a plurality of databases servers. A central configuration management is employed to balance the database load to direct requesting workstations to the appropriate database. Furthermore, this technique is to be implemented using workstations and database servers and configuration controllers connected to a dual network. In such an environment, a central configuration management and a dual network are unavoidable constraints.
FIG. 1
shows the different elements which are present in the Automatic Load Balancing/Backup Function.
The Token Ring User (
100
) activates 2 different Token Ring Data Link Control (DLC) (
102
and
112
) and 2 Token Ring Adapters (
103
and
113
), using the same MAC address, provided the Token Ring Adapters are connected to 2 separate rings (
104
and
114
).
When a remote Token Ring station (
130
) is to be connected to the Token Ring User (
100
), it uses the MAC address as its destination MAC address, and executes a Resolve Procedure to discover the route to the Destination. It first issues an All Route Broadcast Test frame assigned to the MAC address A.
Since the Test frame is sent in All Route Broadcast Mode, it is copied on Token Ring (
104
) by the bridge (
105
) and also on the Token Ring (
114
) by the bridge (
115
). As a consequence, both Token Ring adapters (
103
and
113
) receive a copy of the Test frame, and both respond. The Remote Token Ring Station (
130
) selects the first response and establishes the connection. This connection may be deselected in case it is overloaded or inoperative. Should the occasion arises, the second connection is established.
If the link between the Token Ring user (
100
) and one of the Token Ring DLCs (for example
102
) gets overloaded, this Token Ring DLC (
102
) does not respond to the Resolve procedure and the connection is established via the other Token Ring DLC (
112
). This insures an automatic load balancing between the 2 Token Ring DLCs (
102
and
112
).
If the link between the Token Ring User (
100
) and one of the Token Ring DLCs (for example
102
) gets inoperative, this latter (
102
) does no longer respond to the Resolve procedure, and the connection is established with the other DLC (
112
). This insures an automatic backup between the 2 Token Ring DLCs (
102
and
112
).
FIG. 2
shows the Normal Flow of Mono User Load Balancing.
The Remote Station (
130
) tries to connect to the Token Ring user (
100
). It first issues an All Route Broadcast Test frame assigned to the MAC address A and SAP
0
. The Test frame is then received by DLC No
1
(
102
) and DLC No
2
(
112
).
When the DLC No
1
(
102
) receives the Test frame command, it checks whether a Token Ring user (
100
) is connected to the Token Ring Adapter (
103
). In such case, the DLC No
1
generates a response to the Test frame. This response contains the Routing Info field of route
1
that connects the Token Ring station (
130
) to the Token Ring user (
100
) through the Token Rings (
120
,
104
,
102
).
Conversely, when the DLC No
2
(
112
) receives the Test frame command, it also checks whether a Token Ring user (
100
) is connected to the Token Ring Adapter (
113
). Which is the case in this example. Thus, the Token Ring No
2
(
112
) responds to the Test frame and includes in its response the Routing Info field of route
2
that connects the Token Ring station (
130
) to the Token Ring user (
100
) through the Token Rings (
120
,
114
,
112
).
In our example, the Test response from DLC No
1
(
102
) is received first. The Remote Station (
130
) accepts the first Test frame response it receives, indicating the shortest path, and stores the corresponding route. This route will then be used for the transmission and reception of all frames for this connection between the remote station (
130
) and the Token Ring user (
100
).
In consequence, the Remote Station (
130
) ignores any additional Test frame response that would be received later on for this connection. The Test frame response from DLC No
2
(
112
) is ignored since it is received after the one from DLC No
1
(
102
).
Once the resolve procedure is completed, i.e. the Test frames are exchanged, the Remote Station (
130
) sends an XID frame to the DLC No
1
(
102
). The XID frame which contains the routing information of Route
1
, is transmitted to the Token Ring user (
100
).
If DLC No
1
(
102
) receives an XID frame assigned to Token Ring user (
100
), it checks if this latter is active so as to report it the XID data. If the Token Ring user (
100
) accepts the connection, DLC No
1
(
102
) sends back an XID response to the Remote Station (
130
). This latter sends a SABME command to establish the connection with DLC No
1
(
102
) which responds with a UA response. The connection for the route
1
is then established and the data traffic can begin on this connection.
FIG. 3
describes the Normal flow of a single User Backup.
In this example, the Token Ring user (
100
) is not available on DLC No
1
(
102
) but it is still available on DLC No
2
(
112
).
The remote station (
130
) sends a Test frame in the All Route Broadcast mode assigned to MAC Address A. The Test frame is then received by DLC No
1
(
102
) and DLC No
2
(
112
).
When DLC No
1
(
102
)
Denecheau Lionel
Esteve Denis
Fagiano Christophe
Driggs Lucas Brubaker & Hogg Co. LPA
Ho Duc
Hsu Alpus H.
Lucas James A.
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