The present invention relates to a network interface for converting frame data into a data packet having a prescribed network protocol, more particularly to an arrangement where the network interface converts a data packet having a first prescribed network protocol into a converted data packet having a second prescribed network protocol where the data packets include first cyclic redundancy check digits and second cyclic redundancy check digits, respectively, which were generated by the same cyclic redundancy check generator.
Local area networks use network cables or other network media to link different nodes (e.g., computers, workstations, and servers) across a common network. Local area networks allow different nodes to access other nodes having common peripheral devices (e.g. printers, servers, and modems). Each local area network architecture uses a media access controller (MAC) enabling network interface device (NID) at each network node to share access to the network media. In order to control the operation of the network, the network operates under some form of a standard or protocol, such as an Ethernet protocol.
Traditional Ethernet networks (10BASE-T) operate at 10 Mb/s Ethernet protocol, as described by IEEE Standard 802.3; the majority of Ethernet interfaces currently operate at this data rate. However, a newer Ethernet standard, under IEEE standard 802.3u, accomplishes the faster operation of 100 BASE-T systems, at a 100 Mb/s data rate (i.e., a 125 Mb/s encoded bit rate) using unshielded twisted pair (UTP) physical media. The 100 BASE-T standard defines operation over two pairs of category 5 UTP (100 BASE-TX) and over four pairs of category 3 UTP. The 100 BASE-FX network medium, covered by the 100 BASE-T standard, allows operation over dual fiber optic cabling.
In order to transfer information between nodes in a local area network, data packets are sent. Data packets typically contain a destination address, a source address, a length parameter, data, and cyclic redundancy check (CRC) digits. The destination address and source address parameters indicate the addresses of where the data is being sent from and where the data is being sent to, respectively. The length parameter indicates the length of the data packet. In an Ethernet system, the length can vary from 46 to 1500 bytes. The CRC digits are used to determine if errors occurred in the transmission of the data packet.
In order to transfer data packets between nodes in different local area networks where each of the networks operates according to different prescribed network protocols, the network interface in the first or source local area network converts the data packet into the prescribed network protocol of the second or destination local area network. The first local area network transmits the converted data packet to the second local area network via a backbone. Backbones are used to connect two or more local area networks, allowing data packets to be transmitted between the local area networks.
FIG. 1 illustrates a network interface 10 for converting frame data into a data packet having the prescribed network protocol of the second local area network according to the prior art. A media access controller (MAC) 14 in the network interface 10 receives frame data from a transmit buffer 12. The MAC 14 converts the frame data into a first data packet having a first prescribed network protocol. A first CRC generator 16 in the MAC 14 generates first CRC digits based on the frame data and using coefficients for the first prescribed network protocol 18. The MAC 14 incorporates the CRC digits into the first data packet and sends the first data packet to the logic 20.
The logic 20 converts the first data packet into a converted data packet having a second prescribed network protocol 24. In order to ensure against any errors that occur during transmission, a second CRC generator 22 generates second CRC digits based on the converted data packet and using coefficients for the second prescribed network protocol 24. The logic 20 modifies the converted data packet by replacing the first CRC digits with the second CRC digits. The converted data packet is transmitted by a media independent interface (MII) 26 for transmission onto a backbone via a backbone interface. The backbone is used to transmit the converted data packet to the other local area network, i.e., second or destination local area network.
Requiring the additional CRC generator for generating the second CRC digits requires additional space, which increases the size of the network interface. As a result, if the network interface is manufactured as a single device, the second CRC generator increases the size of the device. Moreover, the second CRC generator is not necessary since the first CRC generator can produce CRC digits having different prescribed network protocols.
There is a need for converting a first data packet having a first prescribed network protocol, where the first data packet includes a first cyclic redundancy check (CRC) digits into a converted data packet having a second prescribed network protocol, where the second data packet includes second CRC digits.
There is also a need for generating second CRC digits using the same CRC generator that generates the first CRC digits.
These and other needs are obtained by the present invention, where a network interface comprises a media access controller (MAC) having a CRC generator configured for generating CRC digits according to different prescribed network protocols, allowing a network interface to transmit a converted data packet in a second prescribed network protocol in response to frame data by a network interface.
According to one aspect of the present invention, a network interface includes a MAC configured for outputting a data packet having a first prescribed network protocol based on a received frame data, where the data packet includes first CRC digits. The MAC includes a CRC generator configured for generating the first CRC digits based on the received frame data. The network interface includes logic configured for converting the data packet in the first prescribed network protocol into a converted data packet having a second prescribed network protocol and second CRC digits generated by the CRC generator. The logic replaces the first CRC digits with the second CRC digits. By using the CRC generator in the MAC, the logic does not require an additional CRC generator to generate the second CRC digits. Moreover, by not requiring the additional CRC generator, the network interface does not need to allocate the space for the additional CRC generator, thereby reducing the overall size of the network interface.
Another aspect of the present invention provides a method for generating CRC digits in a MAC. The method includes receiving a data packet, having a first prescribed network protocol and having CRC digits, by logic from a MAC. A CRC generator in the MAC is configured for generating the first CRC digits based on received frame data. The logic converts the data packet in the first prescribed network protocol into a second prescribed network protocol and provides information relating to the converted data packet to the CRC generator. The CRC generator generates the second CRC digits in response to the information relating to the converted data packet. The logic modifies the converted data packet by replacing the first CRC digits with the second CRC digits. By converting the data packet having a first prescribed network protocol into a data packet having a second prescribed network protocol, the converted data packet can be transmitted to a local area network via a backbone, where the local area network operates according to the second prescribed network protocol. Moreover, the second prescribed network protocol can be a non-IEEE prescribed network protocol.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.