JP2005072933A - Network device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a network device for dynamically changing a maximum segment size in order to improve communication efficiency. <P>SOLUTION: A round trip time measured by an RTT (round trip time) measuring part 104 before starting communication, or a round trip time used at the time of past communication is read from an RTT recording part 105. Communication is started in a maximum segment size determined by an MSS (maximum segment size) determining part 106 on the basis of the round trip time. After this, the round trip time is measured, and an MSS changing part 107 dynamically changes the maximum segment size to an appropriate value on the basis of the round trip time thereby efficiently performing communication all the time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a network device using TCP (Transmission Control Protocol) as a communication protocol.

  As techniques for measuring or changing the window size, MSS (Maximum Segment Size) value and communication speed of data at the time of communication in order to improve the communication efficiency of a network device using TCP as a communication protocol, for example, Reference Documents 1 to 5 It has been known.

  Document 1 is a technique related to an uplink band allocation circuit of a transmission system, and changes transmission band allocation in the case of multiplexing and transmitting by time division, wavelength division, code division, or the like according to a window size.

  Document 2 is a technique for changing the data transmission rate by estimating an RTT (Round Trip Time) value.

  Document 3 is a technique for controlling communication efficiency by changing the window size.

  Document 4 is a technique related to a measuring apparatus and a measuring method for measuring an MSS value.

  Document 5 is a technique for adjusting the amount of data to be transmitted according to the communication history.

  The MSS value is determined when establishing a TCP connection as a unit amount of data to be communicated. Specifically, network devices that communicate with each other transmit and receive connection request packets including MSS values to be used on the communication path as TCP header options, and the smaller value is adopted. Is done. However, the MSS option is not always specified at the time of communication and may not be used. In this case, the network device that has received the TCP header that does not include the MSS option continues the processing assuming that the specified value of 536 bytes is designated as the MSS value.

JP 2000-13424 A JP 2001-119434 A JP 2001-195326 A JP 2000-106557 A JP-A-10-242997

  In general, the larger the MSS value, the higher the communication efficiency because more data can be transmitted in one segment. However, when a remote station is installed at a remote location and communicates via a number of routers, data is re-divided according to the MSS value set for each router, or data is transmitted due to congestion in the communication path. If the transmission fails and re-transmission is required, a large size of one segment may cause a decrease in communication efficiency.

  For this reason, it is desirable to change the MSS value to an optimum value at any time according to communication conditions. Conventionally, however, the MSS value is dynamically changed by using a fixed value or using two types of values depending on whether the communicating station belongs to the local network to which the station belongs. It wasn't.

  Accordingly, an object of the present invention is to provide a network device in which the MSS value is changed to an optimum value, preferably dynamically changed, for the purpose of improving communication efficiency.

  In order to solve the above-mentioned problem, the invention described in claim 1 is a network device that uses TCP as a communication protocol, and includes a measuring unit that measures a round trip time, and the round trip time measured by the measuring unit. And determining means for determining a maximum segment size based on the maximum segment size, and communicating according to the maximum segment size determined by the determining means.

  Invention of Claim 2 is the network apparatus of Claim 1, Comprising: The said largest segment size during communication is determined by the said determination means based on the measurement result measured by the said measurement means during communication The maximum segment size is dynamically changed.

  The invention according to claim 3 is the network device according to claim 1 or 2, further comprising: predetermined information for specifying a communicating partner terminal station; and the partner measured by the measuring unit A recording unit that records the round trip time associated with the terminal station, and when the communication is started, the terminal unit with which the determining terminal communicates with the recording unit records the predetermined information. When it is a station, it includes means for determining the maximum segment size based on the round trip time recorded together with the predetermined information.

  A fourth aspect of the present invention is the network device according to any one of the first to third aspects, wherein the determining means is a table showing a relationship between the round trip time and the maximum segment size created in advance. , And means for determining the maximum segment size based on the round trip time.

  The invention according to claim 5 is the network apparatus according to any one of claims 1 to 3, wherein the determining means performs an operation based on a function indicating a relationship between the round trip time and the maximum segment size. Means for determining the maximum segment size based on the round trip time.

  A sixth aspect of the present invention is the network apparatus according to any one of the first to fifth aspects, wherein the measuring means transmits an ICMP ECHO packet and receives a packet in response thereto. And means for measuring the round trip time.

  A seventh aspect of the present invention is the network device according to any one of the first to fifth aspects, wherein a packet loss rate is used instead of the round trip time. .

  The invention according to claim 8 is the network apparatus according to any one of claims 1, 3 to 6, wherein the number of hops to the partner terminal station is used instead of the round trip time. It is characterized by doing.

  A ninth aspect of the present invention is the network apparatus according to the sixth aspect, wherein the measurement means uses a TCP connection request packet instead of the ICMP ECHO packet.

  A network device using TCP as a communication protocol, comprising: a measuring unit that measures a round trip time; and a determining unit that determines a maximum segment size based on the round trip time measured by the measuring unit, By performing communication using the maximum segment size determined by the determination unit, it is possible to improve communication efficiency as compared with a conventional network device that uses a fixed maximum segment size.

{Embodiment 1}
<Configuration of network device>
FIG. 1 is a diagram showing a hierarchical model of a network device 201 according to Embodiment 1 of the present invention. The network apparatus 201 uses TCP / IP as the communication protocol 101 and is composed of a hierarchy of an upper protocol layer 108, a TCP protocol layer 102, an IP protocol layer 103, and a physical layer 109 as shown in FIG. It is connected. The TCP protocol layer 102 includes an RTT measurement unit 104, an RTT recording unit 105, an MSS determination unit 106, and an MSS change unit 107.

  The RTT measuring unit (measuring unit) 104 measures an RTT value when communicating via the network 110, and notifies the RTT recording unit 105, the MSS determining unit 106, and the MSS changing unit 107 of the measurement result. It has a function.

  The RTT recording unit (recording unit) 105 uses the RTT value notified from the RTT measuring unit 104, together with information such as an IP address and a MAC address for identifying a partner station as a communication partner when the RTT value is measured, It has a function of recording on a storage device such as a nonvolatile memory.

  When starting communication, the MSS determination unit (determination means) 106 searches the RTT recording unit 105 to find out whether or not information related to the partner station at the time of previous communication has been recorded. For example, the RTT value obtained when communication was performed in the past is used, and if not recorded, the RTT value newly measured by the RTT measurement unit 105 is used to determine the MSS value.

  The MSS changing unit 107 has a function of monitoring the RTT value notified from the RTT measuring unit 104 after starting communication and dynamically changing the MSS value according to the change.

  Here, the upper protocol layer 108 and the physical layer 109 specifically correspond to an application and hardware, respectively. These layers and functions are realized by dedicated hardware and software programs.

<Operation of network device>
The network apparatus 201 shown in FIG. 1 is connected to the LAN 205 as shown in FIG. The LAN 205 is connected to another network device such as the host A (202). Further, the LAN 205 is connected to an external network such as the Internet 206, and the Internet 206 includes a host B (203) located close to the network device 201 and a host C (204) located at a remote location. Another network device is connected.

  When communication is performed between the network devices 201 to 204 having the positional relationship shown in FIG. 2, in the conventional method, the MSS value is fixedly used for all communication, or the host A (connected to the LAN 205 ( 202) and the host B (203) and the host C (204) that do not belong to the LAN only use different MSS values fixedly. However, since the MSS value that allows efficient communication depends on the distance between terminal stations that communicate with each other and the load state of the network, the network apparatus 201 determines the MSS value for each partner station, By dynamically changing this according to the change in the communication status, communication is always performed with the optimum MSS value. A specific operation at this time will be described below.

  FIG. 3 is a flowchart showing the operation of the network device 201 in the TCP protocol layer 102. Hereinafter, the operation of the network apparatus 201 will be described with reference to FIG.

  When the network apparatus 201 is in a standby state, if there is a communication request from the upper protocol layer 108, the TCP protocol layer 102 detects this and starts an operation for performing data communication using the network 110. (Step S301).

  In starting data communication, first, the MSS determination unit 106 checks whether or not the RTT recording unit 105 has recorded an RTT value for communication performed in the past with the partner station (step S302).

  At this time, if the RTT value is recorded, the process proceeds to step S306. If the RTT value is not recorded, measurement of the RTT value is newly started. For this purpose, an Internet Control Message Protocol (ICMP) ECHO request packet that is normally used to confirm the establishment of communication is used. That is, the RTT measurement unit 104 generates an ICMP ECHO request packet and transmits it to the partner station via the network 110 via the IP protocol layer 103 and the physical layer 109 (step S303). In response to this, the partner station receives the transmitted ICMP ECHO response packet via the network 110 via the physical layer 109 and the IP protocol layer 103 (step S304). When the received RTT measurement unit 104 calculates an RTT value from the time when the ICMP ECHO packet is transmitted and the time when the packet is received, and notifies the RTT value to the RTT recording unit 105 and the MSS determination unit 106, the RTT recording unit 105 is as described above. The RTT value is recorded on a storage device such as a non-volatile memory together with information such as an IP address and a MAC address for specifying the partner station (step S305).

  The MSS determination unit 106 that has received the recorded RTT value from the RTT recording unit 105 or the measured RTT value from the RTT measurement unit 104 determines the MSS value based on the RTT value (step S306). Specifically, the MSS determination unit 106 refers to a predetermined table created in advance by a combination of an RTT value and an MSS value associated so that the MSS value decreases as the RTT value increases, and the obtained RTT value The MSS value corresponding to is read from this table.

  Next, a TCP connection request is made by designating the determined MSS value (step S307), and after waiting for a response, if a connection is established, data transmission / reception is started (step S308).

  FIG. 4 is an explanatory diagram when the operation at this time (steps S303 to S307) is viewed from transmission / reception of packet data. As described above, the ICMP ECHO request packet is used as the RTT measurement packet, the RTT value is calculated from the time required for the response from the transmission, the MSS value is determined based on this, and the determined MSS value is used. Data communication is started after the TCP connection is established.

  When the data transmission / reception is started, the RTT measurement unit 104 starts measuring the RTT value. Specifically, the RTT value is measured by monitoring and calculating the time when the data packet is transmitted and the time when the response packet indicating that the data packet is received is received. Then, the measured RTT value is notified to the MSS changing unit 107. The MSS changing unit 107 refers to a predetermined table created in advance for the correspondence between the RTT value and the MSS value described above, determines the MSS value based on the notified RTT value, and uses this for data communication. Compare with existing MSS value. When a difference of a predetermined value or more is detected, the MSS value is determined to be changed, and the partner station is requested to start communication with the new MSS value. Are transmitted and received (step S309). The measurement of the RTT value and the determination of the MSS value change are performed every predetermined time, and the MSS value of the data being communicated is dynamically changed according to the result.

  At this time, the RTT measurement unit 104 also notifies the measured RTT value to the RTT recording unit 105, and the RTT recording unit 105 transmits the RTT value to the other party in the same manner as in the operation before the start of communication (step S305). The information is recorded on a storage device such as a nonvolatile memory together with information such as an IP address and a MAC address for specifying the station. This RTT value is used as a record when communication was performed in the past when communication with the same partner station is started later (in the case where there is a record in step S302).

  When the data communication ends (step S310), the original standby state (step S301) is restored.

  In this way, by recording the MSS value set with the partner station that has made communication once, and using this value, an appropriate MSS value can be set from the start of communication. Further, by measuring the RTT value reflecting the communication status for each communicating station and using a table that defines an appropriate MSS value for the RTT value, the hosts A to C (202 to 202) shown in FIG. 204), it is possible to set an MSS value suitable for each communication situation even if the partner station has a different network length or load situation. Further, by dynamically changing the MSS value, it is possible to cope with a network load state that changes from moment to moment, and to perform efficient communication.

{Embodiment 2}
In the first embodiment, the recorded RTT value is read from the RTT recording unit 105 or the newly measured RTT value is read from the RTT measurement unit 104 in the operation steps S302 to S306 of the network apparatus 201 shown in FIG. Upon receipt, the MSS determination unit 106 determines the MSS value based on the RTT value. However, in this embodiment, these operations are not performed, and a TCP connection is established and data transmission / reception is started with an appropriate MSS value set. Specifically, for example, the MSS value may be set to a prescribed value of 536 bytes and data transmission / reception may be started.

  Therefore, at the stage of starting communication, the MSS value is not suitable for communication. However, as described above in Embodiment 1, after starting communication, the RTT value is measured, and the MSS value optimum for communication is obtained. Can be changed.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  In this way, even if communication is started with an appropriate initial value of the MSS value, the MSS value is dynamically changed to the optimal value during communication. The same operation as in the first mode can be realized. Further, if the measurement of the RTT value and the change of the MSS value are performed immediately after the start of data transmission / reception, the same effect can be obtained while omitting a part of the operation of the first embodiment.

{Third embodiment}
In the first embodiment, in order to determine the MSS value, the RTT value is measured and used in the operation steps S303 to S305 of the network apparatus 201 shown in FIG. And use the number of hops. The number of hops refers to the number of routers through which communication is performed between the local station and the partner station. For example, information relating to the number of hops can be obtained from an ICMP ECHO request packet to be transmitted and received. The number of hops can be used instead of the RTT value because the number of hops generally increases as the remote station with which communication is performed is in a remote place, as with the RTT value. Therefore, similarly to the table described in the first embodiment, if a table is created in advance so that the MSS value decreases as the number of hops increases, the MSS value is determined with reference to this table. Can do.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  As described above, it is possible to measure the number of hops instead of the RTT value and determine the MSS value based on the measured number of hops, thereby realizing the same operation as in the first embodiment.

{Embodiment 4}
In the first embodiment, the ICMP ECHO request packet is used to measure the RTT value in the operation steps S303 to S305 of the network apparatus 201 shown in FIG. 3, but in the present embodiment, this is replaced with this. Then, a dummy TCP connection request packet is used. Normally, the network device that has received the TCP connection request packet transmits a connection response packet as a response if the port is open, and a reset segment with the reset flag turned on if the port is not open. That is, when a suitable port is designated and a TCP connection response request packet is transmitted, a response is returned regardless of whether or not the designated port is open. Using this, it is possible to calculate the RTT value from the time when the dummy TCP connection response request packet is transmitted and the time when the response is returned.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  When the port designated by the dummy TCP connection response request packet is opened, the connection response packet is received, and the communication connection using the designated port is established. However, since communication is not actually performed at the port, after calculating the RTT value, a reset segment is transmitted to the port and the connection is discarded.

  As described above, it is possible to measure the RTT value by using the TCP connection response request packet in which an appropriate port is designated, and thereby, the same operation as that of the first embodiment can be realized.

{Embodiment 5}
In the first embodiment, in the operation steps S306 and S309 of the network apparatus 201 shown in FIG. 3, the table showing the correspondence between the RTT value and the MSS value created in advance using the measurement result of the RTT value is referred to. Determine the MSS value. However, in this embodiment, functions are used instead of tables. That is, the MSS value is calculated and determined by substituting the RTT value into a predetermined function. For example, when the RTT value is m, the MSS that is the MSS value is determined by the following equation.
MSS = A / (m + B) ⁿ + C − (1)
Here, A, B, and C are positive numbers and n is a positive integer, and an appropriate number may be determined in advance.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  Note that the function is used instead of the table reference in the operation of the network apparatus 201 shown in FIG. 3 in only one of step S306 and step S309, and the other is a mode of referring to the table. Alternatively, both of them may use a function. Equation (1) is an example based on the qualitative relationship that it is better to communicate with a smaller MSS value as the RTT value is larger, and the function may have other forms. .

  As described above, the same operation as that of the first embodiment can be realized by substituting the RTT value into a predetermined function created in advance.

{Sixth embodiment}
In the first embodiment, the MSS value is determined based on the measurement result of the RTT value, and after the TCP connection is established, data transmission / reception is started. Then, after data transmission / reception is started, in order to dynamically change the MSS value to the optimum value, in the operation step S309 of the network device 201 shown in FIG. 3, the RTT is continued from the time information related to the data to be transmitted / received. Although the value is monitored, in this embodiment, the packet loss rate is used instead of the RTT value. As with the RTT value, the packet loss rate increases as the remote station with which communication is performed is more distant, and as the load on the network increases and the communication becomes more difficult. Therefore, this is monitored during communication. Thus, it can be used instead of the RTT value. Therefore, similarly to the table described in the first embodiment, if a table is created in advance so that the MSS value decreases as the packet loss rate increases, the MSS value is determined with reference to this table. be able to.

  In addition, when the ACK signal indicating that the data has been normally received is not transmitted from the partner station that transmitted the packet data even after a predetermined time has elapsed, the data is retransmitted as having been lost, The packet loss rate in this embodiment refers to the ratio of packet data retransmitted due to data loss to the packet data transmitted by the local station.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  In this way, it is possible to measure the packet loss rate instead of the RTT value and dynamically change the MSS value based on this, thereby realizing the same operation as in the first embodiment. it can.

{Embodiment 7}
In Embodiment 1 or 5, the MSS value is determined based on the measurement result of the RTT value, and after the TCP connection is established, data transmission / reception is started. Even after the transmission / reception of data is started, the RTT value or the packet loss rate is continuously monitored and the MSS value is dynamically changed to the optimum value. After the MSS value is determined and data transmission / reception is started, the MSS value is not changed. That is, step S309 is omitted in the operation of the network device 201 shown in FIG.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  In this way, the MSS value is not dynamically changed continuously, and the MSS value determined when starting communication is used, so that the MSS changing unit 107 is omitted in the configuration of the network device 201 shown in FIG. However, the effect of setting an appropriate MSS value for each communicating station can be maintained with a simple device configuration.

{Embodiment 8}
In the first embodiment, in the operation step S305 of the network apparatus 201 shown in FIG. 3, the information for identifying the communicating partner station and the RTT value are recorded together and the communication is started later. With reference to the recorded information, if the partner station is a station that has communicated in the past, the MSS value is determined based on the recorded RTT value. However, in the present embodiment, the RTT value is not recorded, and therefore the record of the communication partner when starting communication is not searched. That is, in the operation of the network device 201 shown in FIG. 3, step S302 and recording of the RTT value in step S305 are omitted.

  In addition, since the configuration and operation of the apparatus are the same as those in the first embodiment, description thereof is omitted.

  In this way, by not recording the information related to the RTT value or the number of hops and the partner station, the RTT recording unit 105 and the non-volatile memory for recording can be omitted in the configuration of the network device 201 shown in FIG. Even when a suitable MSS value is set for each communicating station and data communication is started, the effect of continuously changing the MSS value dynamically to the optimum value can be maintained. .

{Embodiment 9}
In the second to seventh embodiments, a part of the first embodiment is changed. However, the present invention is not limited to the case where each embodiment is implemented alone, and the contents of each embodiment described above are two or more. The same operation as in the first embodiment may be realized in combination.

It is a figure which shows the hierarchy model of the network apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the network which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the network apparatus based on Embodiment 1 of this invention. It is a figure which shows transmission / reception of the packet of the network device based on Embodiment 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Communication protocol layer, 102 TCP protocol layer, 103 IP protocol layer, 104 RTT measurement part, 105 RTT recording part, 106 MSS determination part, 107 MSS change part, 108 Higher protocol layer, 109 Physical layer, 110 network, 201 Network apparatus 202 Host A, 203 Host B, 204 Host C, 205 LAN, 206 Internet.

Claims (9)

A network device that uses TCP as a communication protocol,
A measuring means for measuring the round trip time;
Determining means for determining a maximum segment size based on the round trip time measured by the measuring means;
With
Communication is performed according to the maximum segment size determined by the determination means. The network device according to claim 1,
The network apparatus, wherein the maximum segment size during communication is dynamically changed to the maximum segment size determined by the determination unit based on a measurement result measured by the measurement unit during communication. The network device according to claim 1 or 2, further comprising:
Recording means for recording predetermined information for identifying a communicating partner terminal station, and the round trip time relating to the partner terminal station measured by the measuring means;
With
When starting communication, the determining means
Means for determining the maximum segment size based on the round trip time recorded together with the predetermined information, when the partner terminal station for communication is the terminal station that has recorded the predetermined information by the recording means;
A network apparatus comprising: A network device according to any one of claims 1 to 3,
The determining means includes
Means for determining the maximum segment size based on the round trip time by referring to a table showing a relationship between the round trip time and the maximum segment size created in advance;
A network apparatus comprising: A network device according to any one of claims 1 to 3,
The determining means includes
Means for determining the maximum segment size based on the round trip time by performing an operation with a function indicating a relationship between the round trip time and the maximum segment size;
A network apparatus comprising: A network device according to any one of claims 1 to 5,
The measuring means includes
Means for measuring the round trip time by sending an ICMP ECHO packet and receiving a packet in response thereto;
A network apparatus comprising: A network device according to any one of claims 1 to 5,
A network device characterized by using a packet loss rate instead of the round trip time.   7. The network device according to claim 1, wherein the number of hops to a partner terminal station is used instead of the round trip time. A network device according to claim 6 or claim 8, wherein
The measuring means includes
A network apparatus, wherein a TCP connection request packet is used instead of the ICMP ECHO packet.

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