KR20000034483A - Method for transmitting data packet of built-in type cable modem - Google Patents

Abstract

PURPOSE: A method for transmitting data packet of built-in type cable modem is provided so that the data transmission of high speed is possible since the efficiency of the MPU bus can make increase by reducing an amount of data being transmitted between a MAC chip and MPU which are equipped within the built-in type cable modem. CONSTITUTION: A method for transmitting data packet of built-in cable modem includes several steps. When MAC chip (140) receives data packet from CPE or CMTS, a step is to store the head information of the received packet to a memory (170), and to store the rest data to a local memory buffer (141). A step is that the MPU (160) reads the stored head information, operates various processes and stores the processed result to the memory (170). A step is that the MAC chip (140) reads the processed result stored to the memory (170) and discriminates whether the data packet transmits. If the transmission of the data packet is determined, the MAC chip (140) reads the data stored to the local memory buffer (141) and after attaching a header, transmits the data to the CPE or CMTS.

Description

A method for transmitting a data packet in a built-in cable modem

The present invention relates to a data packet forwarding method of an embedded cable modem, and more particularly, to a data packet forwarding method of an embedded cable modem capable of reducing the amount of data transmitted through a microprocessor unit (MPU) bus.

In general, the cable modem network is a network system that is attracting attention together with ISDN, multi-digital subscriber line (xDSL), etc. in the field of remote access, and is connected to the Internet and intranet to subscribers at a high speed of Mbps. It provides various services such as telecommuting, video conferencing, and web search.

The concept of cable modem networks, which have a wide user base in the United States, is to bring cable TV (CATV) networks into the data communication field. In terms of using coaxial cables, they are similar to each other. A cable modem network connects a coaxial cable to a personal computer (PC) via a cable modem, while connecting the TV to the set-top box after connecting the box. At this time, there may be one PC or multiple PCs connected to the cable modem.

Cable modems are divided into workgroup, multiuser, and personal. Workgroup cable modems are designed for small groups with 4 or 8 ports for connecting PCs, enabling them to build small LANs, and multi-user cable modems for libraries and schools. It is used in relatively large places such as factories and factories.

1 is a schematic configuration diagram of a general cable modem network, in which a plurality of cable modems 11 to 14 (CM: Cable Modem) are connected to a cable network 20, and each cable modem 11 to 14 is connected to a subscriber. A personal computer (PC), which is a customer premises equipment (CPE), is connected, and a cable modem terminal system (CMTS) 30 is connected between the cable network 20 and the backbone network 40. . Here, the subscriber receives a service such as the Internet from the backbone network 40.

The cable modems 11 to 14 (CM) are configured to store packets of an upstream channel input from a PC and downstream channels of a downstream channel input from the CMTS 30. Not stored) so that the subscriber can receive various services from the backbone network 40 connected to the CMTS 30.

The CMTS 30 is located at the head end to provide an uplink channel and a downlink channel. The CMTS 30 transmits broadband data at a rate of 500 Kbps to 30 Mbps through a downlink channel, and each cable modem 11 to 14 and CM transmits at 96 Kbps to 10 Mbps over an uplink channel. Receive narrowband query data.

Meanwhile, the cable modem includes an external cable modem installed outside the CPE (PC) and connected through the CPE and an Ethernet interface, and an internal cable modem embedded in the CPE. PCI bus interface controller for interfacing with the Programmable Communication Interface (PCI) bus in the CPE, which is connected to the MPU bus with a medium access control chip (MAC chip), MPU, and memory that transmits and receives data packets to and from the CMTS 30. Is also connected to the MPU bus.

When the embedded chip modem of the prior art configured as described above receives the data packet from the CPE or CMTS, the MAC chip stores both the header information and the data of the packet in the memory and informs the MPU of the fact. The MPU notified of the existence of the data packet from the MAC chip reads header information and data from the memory, performs processing such as packet filtering, address verification, bridging, and stores the data again in the memory. Inform the MAC chip. The MAC chip notified of the completion of the packet processing from the MPU reads the packet appropriately processed by the MPU from the memory and determines whether to transmit the data packet. Here, when the CPE side transmission of the data packet is determined, the MAC chip attaches a header to the packet, stores it in memory, and then informs the PCI bus interface controller of the fact. The PCI bus interface controller notified of the data packet transmission from the MAC chip reads the transmission packet stored in the memory and transfers it to the PCI bus of the CPE.

However, as described above, since the MAC chip, the MPU, and the PCI bus interface controller provided in the integrated cable modem transmit and receive the entire data packet through the MPU bus, the packet processing such as filtering or bridging is performed. Due to the low efficiency of the bus, it takes a relatively long time to process data packets, and therefore, there is a problem in that the cable modem cannot effectively implement the high data rate that is desired.

The present invention has been made to solve the above problems, the MAC chip, the MPU and PCI bus interface controller to move only the header information required for packet processing instead of moving the entire packet when sending and receiving data packets for packet processing Its purpose is to provide a data packet delivery method for the built-in cable modem that can reduce the amount of data transferred through the MPU bus by storing the rest in the local memory buffer of the MAC chip.

In order to achieve the above object, in the data packet delivery method of the integrated cable modem according to the present invention, a MAC chip, an MPU, and a memory for transmitting and receiving data packets with a CPE or CMTS are connected to an MPU bus, and the local memory in the MAC chip. In the data packet transfer method of a built-in cable modem in which a buffer is connected, a PCI bus interface controller for interfacing with a PCI bus provided in the CPE is embedded in the MAC chip, wherein the MAC chip from the CPE or CMTS Receiving a data packet, storing header information of the packet in the memory, and storing the remaining data in the local memory buffer; A second step of the MPU reading the header information stored in the memory to perform various processes and storing the processing result in the memory; A third step of the MAC chip reading the processing result stored in the memory to determine whether to transmit the data packet; When the transmission of the data packet is determined, the MAC chip reads the data stored in the local memory buffer, attaches a header, and transmits the data packet to the CPE through the embedded PCI bus interface controller or to the CMTS. It is done.

1 is a schematic diagram of a typical cable modem network;

2 is a schematic diagram of a built-in cable modem to which the present invention is applied.

<Description of the symbols for the main parts of the drawings>

140: MAC chip (Medium Access Control chip) 141: local memory buffer

160: Microprocessor Unit (MPU) 170: Dynamic RAM (DRAM)

200: MPU bus

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The built-in cable modem to which the present invention is applied uses the Internet Protocol (IP) and has a hierarchical structure as shown in Table 1 below for transparent transmission of IP messages.

Hierarchy Tier Network layer - Data link layer Logical Link Control (LLC) Sublayer Link Security Sublayer Medium access control (MAC) sublayer Physical layer Transmission Convergence (TC) Sublayer Physical Media Dependent (PMD) Sublayer

That is, the cable modem has a vertical hierarchical structure of a network layer, a data link layer, and a physical layer. The data link layer is divided into a logical link control (LLC) sublayer, a link-security sublayer, and a medium access control (MAC) sublayer, and the physical layer is transmitted. It is divided into a convergence sublayer and a physical medium dependent (PMD) sublayer. The network layer (IP layer) transmits IP traffic.

The media access control (MAC) sublayer of the data link layer supports a protocol data unit (PDU) of variable length. Here, the MAC protocol has a feature of controlling bandwidth allocation by the CMTS, upstream is divided into mini slots of a predetermined time interval, and supports variable length packets to increase bandwidth usage efficiency.

The transport convergence (TC) layer of the physical layer is present only in the downstream to provide additional services such as digital video, and the physical media dependent (PMD) sublayer is a modulation scheme of 64QAM and 256QAM in the downstream. It supports functions such as error correction codes of Solomon and Trellis, and supports upstream QPSK and 16QAM modulation schemes, TDMA, fixed length frames and variable length PDUs.

On the other hand, the MAC frame exchanged between the cable modem and the CMTS consists of a MAC header defining the contents of the MAC frame, and a data PDU whose length and presence are determined according to the MAC header. The MAC frame is transmitted with a physical medium dependent (PMD) sublayer over header in front of the MAC header in the upstream and an MPEG transport header in the downstream.

2 is a schematic diagram of a built-in cable modem to which the present invention is applied. The built-in cable modem includes a tuner 110, a modulator 120, a demodulator 130, a MAC chip 140, and a local memory. A buffer 141, an encryptor / decoder 150, an MPU 160, a DRAM (Dynamic RAM, 170), and a flash memory (180) are provided. The MAC chip 140, the MPU 160, the DRAM 170, and the flash memory 180 are respectively connected to the MPU bus 200, and the PCI chip interface controller 140a is built in the MAC chip 140. It is.

It will be described in detail the process of transmitting the data packet according to an embodiment of the present invention is built-in cable modem configured as described above.

First, a process of processing the data packet received from the CMTS by the embedded cable modem is as follows.

The tuner 110 receives the RF signal (data packet) transmitted by the CMTS through the F-connector and outputs it to the demodulator 130. The demodulator 130 demodulates the received RF signal (16QAM modulated signal). The MAC chip 140 filters the received data packet (MAC frame), and then the header information of the packet is stored in the DRAM 170 through the MPU bus 200 and the remaining data. Stores the data packet in the local memory buffer 141 and informs the MPU 160 that a data packet exists.

When the MPU 160 is notified of the presence of a data packet from the MAC chip 140, the MPU 160 reads the header information stored in the DRAM 170 through the MPU bus 200, and processes only packet information such as packet filtering, address verification, bridging, and the like. After the processing is performed, the result is again stored in the DRAM 170 through the MPU bus 200, and the MAC chip 140 is notified of the completion of packet processing.

When the MAC chip 140 is notified of the completion of packet processing from the MPU 160, the MAC chip 140 reads the processing result of the MPU 160 stored in the DRAM 170 through the MPU bus 200 and transmits a data packet to the CPE side. Decide

Since the MAC chip 140 and the MPU 160 exchange only header information of the data packet through the MPU bus 200 and the DRAM 170, the amount of data transferred through the MPU bus 200 is greatly reduced.

Thereafter, when the CPE side transmission of the data packet is determined, the MAC chip 140 reads data stored in the local memory buffer 141, attaches a header, and transmits the data packet to the CPE side through the embedded PCI bus interface controller 140a. Here, since the PCI bus interface controller 140a is embedded in the MAC chip 140 instead of being connected to the MPU bus 200, the MAC chip 140 and the PCI bus interface controller 140a are connected to the MPU bus 200 and the DRAM. There is no need to send and receive data packets through 170 to help reduce the amount of data transferred through the MPU bus 200.

Next, the internal cable modem processes the data packet received from the CPE as follows.

The MAC chip 140 receives and filters the data packet transmitted by the CPE through the built-in PCI bus interface controller 140a, and then stores the header information of the packet in the DRAM 170 through the MPU bus 200 and the rest. After the data is stored in the local memory buffer 141, the MPU 160 notifies that a data packet exists. In this case, since the PCI bus interface controller 140a and the MAC chip 140 do not need to exchange data packets through the MPU bus 200 and the DRAM 170, the amount of data transferred through the MPU bus 200 is determined. Can help to reduce

When the MPU 160 is notified of the presence of a data packet from the MAC chip 140, the MPU 160 reads the header information stored in the DRAM 170 through the MPU bus 200, and processes only packet information such as packet filtering, address verification, bridging, and the like. After the processing is performed, the result is again stored in the DRAM 170 through the MPU bus 200, and the MAC chip 140 is notified of the completion of packet processing.

When the MAC chip 140 is notified of the completion of packet processing from the MPU 160, the MAC chip 140 reads the processing result of the MPU 160 stored in the DRAM 170 through the MPU bus 200 and transmits a data packet to the CMTS. Decide

In the above, since the MAC chip 140 and the MPU 160 exchange only header information of the data packet through the MPU bus 200 and the DRAM 170, the amount of data transferred through the MPU bus 200 is greatly reduced.

Then, when the transmission of the CMTS side of the data packet is determined, the MAC chip 140 reads the data stored in the local memory buffer 141, attaches a header to the modulator 120, and transmits the modulator 120 to the MAC chip. The 16QAM modulated data packet received from the 140 is output to the tuner 110, and the tuner 110 transmits the 16QAM modulated uplink packet to the CMTS through the F-connector.

In addition, when transmitting a data packet to the CMTS, the encryptor / decoder 150 shown in FIG. 2 encrypts the contents of the packet so that other cable modems cannot know, and decrypts the encrypted data packet received from the CMTS.

As described above, the present invention can increase the efficiency of the MPU bus by reducing the amount of data transferred between the MAC chip and the MPU included in the embedded cable modem, thereby enabling high-speed data transmission of the embedded cable modem.

Claims (1)

PCI bus interface for interfacing with a PCI bus, a MAC chip, an MPU, and a memory for transmitting and receiving data packets to and from a CPE or CMTS, and a local memory buffer connected to the MAC chip, and a PCI bus provided in the CPE. In the data packet transmission method of the integrated cable modem in which the controller is embedded in the MAC chip, When the MAC chip receives a data packet from the CPE or CMTS, storing the header information of the packet in the memory and storing the remaining data in the local memory buffer; A second step of the MPU reading the header information stored in the memory to perform various processes and storing the processing result in the memory; A third step of the MAC chip reading the processing result stored in the memory to determine whether to transmit the data packet; When the transmission of the data packet is determined, the MAC chip reads the data stored in the local memory buffer, attaches a header, and transmits the data packet to the CPE through the embedded PCI bus interface controller or to the CMTS. Data packet transmission method of the built-in cable modem.