Local area network

Details Local area network Local area network

1997-04-09

2001-07-03

Rao, Seema S. (Department: 2732)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S420000, C370S502000, C709S249000

Reexamination Certificate

active

06256312

ABSTRACT:

TECHNICAL FIELD
This invention relates to local area network communication systems.
BACKGROUND OF THE INVENTION
A variety of designs have been utilized for local area network (LAN) communication systems. One local area network communication system is depicted in FIG.
1
. The system depicted in
FIG. 1
may be termed a bus based Ethernet LAN broadcast system. User stations
13
,
15
,
17
and
19
are each connected to bus
11
. When, for example, user
13
wishes to communicate, he transmits information to bus
11
. The information is potentially available to users
15
,
17
and
19
. The user having the correct destination address receives and interprets the information. (If the system is equipped with a security feature, other users who have different destination addresses presumably cannot access the information.)
Another popular system is depicted in FIG.
2
. Reference numeral
21
denotes a multiple port repeater based Ethernet LAN. The configuration depicted in
FIG. 2
is often termed a “star topology.” Users
23
,
25
,
27
,
29
,
31
and
33
are each connected to a single, multiport repeater
21
. Should user
23
, for example, wish to transmit information, the information is transmitted to repeater
21
. Repeater
21
rectifies various forms of signal degradation which may have occurred during transmission and then broadcasts the information to users
25
,
27
,
29
,
31
and
33
. The user having the correct destination address receives and interprets the information, while users with different destination addresses either: (i) receive the information anyway, or (ii) cannot receive the information because a security feature prevents them from receiving it due to their incorrect destination addresses.
Both of the systems depicted in
FIGS. 1 and 2
have several shortcomings. Each system is a collision-based system. Thus, when one user, for example, user
23
or user
13
, is transmitting information, other users cannot transmit. Should another user attempt to transmit, a collision results and the other user's transmitter backs off and waits for another opportunity to transmit. Thus, only a single user may transmit at any given time period.
In both the systems depicted in FIG.
1
and
FIG. 2
, a single medium, either bus
11
or multiport repeater
21
is shared by all users.
Each of the systems in FIG.
1
and
FIG. 2
is theoretically capable of handling a large number of users, for example, as many as 1,024 users. However, because of the collision problem, as the number of users increases, the effective bandwidth per user decreases. In other words, as the number of users increases, the efficiency of the system in transmitting information decreases.
SUMMARY OF THE INVENTION
The present invention serves to alleviate the above-mentioned problems. The invention illustratively includes a plurality of buses, each bus having a respective plurality of user stations connected to it. Each user station is capable of either sending or receiving packets of information having destination addresses. A multiport bridge router connects the buses. The multiport bridge router is capable of directing information packets from one bus to another one in accordance with the destination address of the packet.
Another embodiment of the invention includes a single bus together with a plurality of addressable user stations, each station having a respective media access controller capable of recognizing packets of information having the respective user station's address. Each user station is connected through its respective controller to the bus. Furthermore, a memory is connected to the bus. Information packets transmitted from a first user station with respective controller are sent to the memory by the bus and subsequently received by a second controller associated with respective second user station.


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ISO/IEC 8802-3 Information Processing Systems Local area Networks.

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