Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-05-26
2001-11-27
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S466000, C370S467000, C370S475000
Reexamination Certificate
active
06324178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. F
IELD OF THE
I
NVENTION
The present invention relates to the field of communication systems. The present invention relates to communication systems having differing communication domains. In one embodiment, the present invention relates to communication systems including local area networks (LANs) using the Ethernet communication protocol (e.g., the IEEE 802.3 Standard) and systems using the IEEE 1394 serial communication bus standard.
2. R
ELATED
A
RT
Networked communication systems (“networks”) are very popular mechanisms for allowing multiple computers and peripheral systems to communicate with each other within larger computer systems. Local area networks (LANs) are one type of networked communication system and one type of LAN utilizes the Ethernet communication standard (IEEE 802.3). One Ethernet LAN standard is the 10 BaseT system which communicates at a rate of 10 Megabits per second and another Ethernet LAN standard, 100 BaseT, communicates at a rate of 100 Megabits per second. Computer systems can also communicate with coupled peripherals using different bus standards including the Peripheral Component Interconnect (PCI) bus standard and the Industry Standard Architecture (ISA) and Extended Industry Standard Architecture (EISA) bus standards. Recently, the IEEE 1394 serial communication standard has become a popular bus standard adopted by manufacturers of computer systems and peripheral components for its high speed and interconnection flexibilities. Each of the above communication standards communicates data packets using its own data packet format. Unfortunately, data packet formats are not necessarily compatible from one communication standard to another.
Due to the many communication standards available within computer systems and communication systems, it is often the case that one computer (or device) of one communication standard or “domain” needs to communicate with another computer (or device) of another communication domain. Since the data packet formats (e.g., data frame formats) between differing communication standards are not necessarily compatible, bridge circuits have been used in the prior art to allow communication from one communication domain to another. The bridge circuit is physically coupled between the two communication domains and is thereby made available to receive and send data packets for each communication domain.
FIG. 1A
illustrates one exemplary bridge circuit
10
of the prior art that is used to provide communication between communication domain “A”
20
a
and communication domain “B”
20
b
that have incompatible data packet formats. An exemplary data flow direction is shown for data packets (“packets”) originating from communication domain “A”
20
a
and destined for communication domain “B”
20
b
. The bridge circuit
10
contains a first memory unit
12
for receiving the header, data payload and trailer portions of a data packet from domain A
20
a
. A second memory unit
16
is also included. Once a data packet from domain A
20
a
is received, the data processor circuit
14
reads each byte of the stored data packet and transforms the data packet into the format compatible for domain B
20
b
. As the data processor circuit
14
transforms the data packet to the format for domain B
20
b
, the data packet is read, byte-by-byte, from memory
12
and copied into the second memory
16
. For instance, the header is read from memory
12
, processed, and stored in memory
16
. Likewise, the data payload section is read from memory
12
, transformed and stored in memory
16
along with the trailer. Once the new data packet is assembled in memory
16
and compatible with domain B
20
b
, it is transmitted to controller circuits which forward the packet to domain B
20
b.
While this prior art bridge circuit
10
of
FIG. 1A
provides a mechanism for transferring data from one communication domain to another, it is inefficient because much of the information of the original data packet is copied into memory twice (e.g., “recopied” once received). For instance, the data is copied into memory
12
when received and then copied, again, into memory
16
when assembling the new packet format. These two copy processes increase the time required for the bridge circuit
10
to provide communication between domain A
20
a
and domain B
20
b
because the received data packet is copied twice. Also, these two copy processes increase the memory resource requirements of the bridge circuit
10
because different memory spaces are required for storing the original packet and its reassembled and translated version.
While bridge circuit
10
of
FIG. 1A
illustrates only the circuitry required to provide communication in one direction, e.g., from domain A
20
a
to domain B
20
b
,
FIG. 1B
illustrates the components required for a bridge circuit
10
′ that allows simultaneous bidirectional communication flow. To allow the forward flow of information, bridge circuit
10
′ requires two memories, a first memory
12
a
to receive a packet from domain A
20
a
and a second memory
16
a
to receive its translated version destined for domain B
20
b
. To allow the simultaneous reverse flow of information, bridge circuit
10
′ requires two more memories, a third memory
16
b
to receive a packet from domain B
20
b
and a fourth memory
12
b
to receive its translated version destined for domain A
20
a
. Therefore, the two copy processes described above also increase the memory requirements for bridge circuit
10
′ to allow simultaneous bi-directional communication.
Accordingly, the present invention provides an efficient data transfer method between communication domains of differing data packet formats. The method of the present invention eliminates one of the above two copy processes when performing a data transfer between communication domains of differing data packet formats. Therefore, the bridge circuit of the present invention has reduced memory resource requirements and also operates faster compared to the prior art bridge circuits. These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein.
SUMMARY OF THE INVENTION
A method is described herein for efficient data transfers between domains of differing data formats. In one exemplary implementation, the data transfer is performed with respect to an IEEE 1394 communication domain and an Ethernet communication domain. During the process for assembling the new data packet, the data transfer method of the present invention advantageously eliminates the need to copy the data payload section of a received data packet from one memory region to another memory region within a bridge device coupled between first and second communication domains. Because the bridge circuit of the present invention eliminates one of the copy processes required of the prior art, the present invention has reduced memory resource requirements and also operates faster compared to the prior art bridge circuits.
Specifically, the header, data payload and trailer sections of a received data packet (of a first communication domain format) are copied into a first portion of memory within the bridge device. Under software control, the present invention then causes the bridge device to construct a new header, of a second communication domain, and appends a pointer to the new header that points to the data payload location within the first portion of memory. The new header includes a destination address obtained from the data payload location a source address of the bridge device and can include the length of the data payload section. A new packet of the second communication domain is then assembled from the newly constructed header and the pointer. The bridge device then transmits the new header section to the second communication domain and forwards the data payload therewith using the pointer as a reference. Domain interface controller circuits then add the new trailer, as
Cheng Pauline
Lo Burton B.
Pan Anthony L.
3Com Corporation
Chin Wellington
Duong Frank
Wagner, Murabito & Hao
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