Packet transmission device and packet transmission method
Aiming to shorten the transmission operation, the present invention provides an apparatus including a memory, a checksum calculation circuit, and a transmission device. The memory stores data of a packet to be transmitted. The checksum calculation section reads data sets corresponding to all the packet fragments except for that having a checksum storage area, sequentially and cumulatively adds the data sets to obtain a checksum value, thereafter reads a data set corresponding to the fragment having the checksum storage area therein from the memory, and adds the read data to the checksum value to obtain a final checksum value. The transmission section sequentially transmits the fragments once the individual fragments are used for the checksum calculation in the checksum calculation section, and, thereafter, transmits the fragment which is read from the memory and has the checksum storage area including the final checksum value therein.
1 . A packet transmission device for transmitting a packet having in a header thereof a checksum storage area after dividing the packet into a plurality of fragments, comprising:
a memory section for storing data of the packet;
a checksum calculation section for reading from the memory section data sets respectively corresponding to all the plurality of fragments except for a fragment having the checksum storage area therein, for sequentially and cumulatively adding the data sets to obtain a checksum value, for reading a data set of the fragment having the checksum storage area therein from the memory section, and for adding the read data set to the checksum value to obtain a final checksum value;
a transmission section for sequentially transmitting the individual fragments having been read from the memory section once the fragments are used for the checksum calculation in the checksum calculation section, and for transmitting, after all the fragments except for the one have been transmitted, the fragment having been read from the memory section and having therein the checksum storage area in which the final checksum value is stored; and
a control section for performing control to read the data of the packet from the memory section and to provide the read data to the checksum calculation section and the transmission section.
2 . The packet transmission device according to claim 1 , wherein
after the sequential transmission of the fragments by the transmission section, the control section controls the checksum calculation section by creating a pseudo-header and writing the pseudo-header in the memory section so that the checksum calculation section can perform on the pseudo-header the cumulative addition to obtain the checksum value.
3 . The packet transmission device according to claim 1 , wherein
the control section controls the checksum calculation section by creating a pseudo-header in advance and writing the pseudo-header in the memory section so that the checksum calculation section can use the pseudo-header as an initial value for the cumulative addition to obtain the checksum value.
4 . The packet transmission device according to claim 2 , wherein
the control section is provided with a pointer for indicating an access position in the memory section, and updates the pointer so as to control access to data to be calculated by the checksum calculation section and data to be transmitted by the transmission section.
5 . The packet transmission device according to claim 3 , wherein
the control section is provided with a pointer for indicating an access position in the memory section, and updates the pointer so as to control access to data to be calculated by the checksum calculation section and data to be transmitted by the transmission section.
6 . A packet transmission method for transmitting a packet having in a header thereof a checksum storage area after dividing the packet into a plurality of fragments, comprising the steps of:
calculating a checksum value by sequentially and cumulatively adding data sets respectively corresponding to all the plurality of fragments except for a fragment having the checksum storage area therein, while sequentially transmitting the fragments once the individual fragments are used to obtain the checksum value; and
storing in the checksum storage area a final checksum value obtained by adding to the checksum value a data set corresponding to the fragment having the checksum storage area therein, and then transmitting the fragment having the checksum storage area therein.
7 . The packet transmission method according to claim 6 , further comprising the step of:
creating a pseudo-header between the step of sequentially transmitting the fragments and the step of transmitting the fragment having the checksum storage area therein, wherein
the cumulative addition to obtain the checksum value is performed on the pseudo-header.
8 . The packet transmission method according to claim 6 , further comprising the step of:
creating in advance a pseudo-header before data sets respectively corresponding to all the plurality of fragments except for the fragment having the checksum storage area therein are sequentially and cumulatively added, wherein
the pseudo-header is used as an initial value for the cumulative addition to obtain the checksum value.
9 . A packet transmission method by using a network protocol for transmitting and receiving a packet having in a header thereof a checksum storage region after dividing the packet into a plurality of fragments, comprising the steps of:
calculating a checksum value by sequentially and cumulatively adding data sets respectively corresponding to all the plurality of fragments except for a fragment having the checksum storage area therein;
sequentially transmitting the fragments except for the one once the individual fragments are used for the checksum calculation;
obtaining a final checksum value by adding to the checksum value the data set corresponding to the fragment having the checksum storage area therein after the transmission of all the fragments except for the one;
storing the obtained final checksum value in the checksum storage area; and
transmitting the fragment having the checksum storage area therein.