JP2006253750A - Method of measuring delay difference of path - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for measuring a difference in delay time at the time of handover individually for transmission to a communication opposite party and reception from a communication opposite party. <P>SOLUTION: A means is provided, for setting a transmission source of a response time measuring packet and any one address of a plurality of network interfaces. Thus, a transmission path for transmitting the response time measuring packet to the communication party and a reception path for receiving a response to the response time measuring packet from the communication party are independently designated, and a reciprocating delay time is measured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring a round trip delay time with a communication partner by transmitting a response time measurement packet and measuring the response time in a packet data communication terminal.

  Wireless LANs have become widespread, and wireless LANs are used not only for data communication but also for voice communication. In particular, due to low power consumption and miniaturization of chips, a plurality of network interfaces such as a wireless LAN and Bluetooth have been mounted on mobile phones that have been considered difficult to mount.

  In a portable terminal having two or more network interfaces represented by a dual terminal, in particular, a wireless network interface, a wireless network interface that can be used differs depending on a communication location. A handover function for switching to a wireless network interface has attracted attention. In particular, with the spread of the Internet, voice calls are also rapidly shifting from conventional circuit-switched networks to IP packet networks using VoIP technology.

  In an IP packet network, the characteristics of the line vary greatly depending on the route, and the number of hops, device performance, line thickness, asymmetry of ADSL and wireless LAN, buffering delay due to power saving mode, etc. vary greatly. When changing, the average delay due to the route before and after the handover changes greatly.

  A streaming application typified by VoIP expects to receive data at regular intervals, and data that arrives after a certain allowable range is discarded. Therefore, if switching is simply performed without considering the delay difference at the time of handover, the delay difference greatly changes at the moment of switching, so that the packet is discarded and noise is generated.

  Therefore, in a terminal handling a streaming application on an IP packet network such as VoIP, the network delay difference before and after the handover is measured in advance so that the application does not discard the packet. It is important to keep it within range.

In particular, in an IP packet network, the time until a packet reaches the communication partner and the time until the packet is received from the communication partner are not necessarily the same. (1) There is a physically asymmetric network such as ADSL (3) There is a physically asymmetric network depending on the direction (3) Wireless LAN and antenna characteristics are different There are some differences between upstream and downstream (4) The amount of control packets varies depending on the direction, as in the power saving mode of wireless LAN.

  In this way, in a network where the delay differs between transmission and reception, the network delay difference before and after handover is measured separately for transmission and reception, and transmission and reception are performed so that the application does not discard packets. It is important to keep it within the allowable range independently.

  As a prior art, as described in Patent Document 1, a method using a ping command has been developed as a method for estimating line quality from a round trip delay with a communication partner.

  Also, as described in Patent Document 2, a technique for measuring network delay by synchronizing time between communication devices using NTP (Network Time Protocol) has been developed.

JP 2002-290436 A JP 2003-324433 A

  However, since the method disclosed in Patent Document 1 measures only the round trip delay with the communication partner, the transmission characteristic to the communication partner and the reception characteristic from the communication partner are different, such as the Internet. Therefore, there is a problem that transmission and reception cannot be estimated separately.

  Since the method disclosed in Patent Document 2 can synchronize time between all communication devices that implement NTP by using NTP, theoretically it calculates the difference between the transmission time and the reception time of the packet. Thus, the one-way delay time can be measured. However, since NTP time synchronization has only an accuracy of about several hundreds of ms at most, it cannot be applied to VoIP which must be suppressed within several tens of ms as a delay allowable range at the time of handover in order not to generate noise.

  The present invention has been devised to solve the above problems, and provides means for separately measuring a delay time difference during handover to transmission to a communication partner and reception from the communication partner.

  In order to achieve the above object, the present invention has a means for setting a source address of a response time measurement packet to any one of a plurality of network interfaces, thereby sending the response time measurement packet to a communication partner. The round trip delay time is measured by independently specifying the transmission path and the reception path when receiving a response to the response time measurement packet from the communication partner.

  According to the present invention, it is possible to separately measure a path delay difference when a communication terminal having a plurality of network interfaces performs a handover, and a transmission delay difference to a communication partner and a reception delay difference from the communication partner. Became.

  Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment]
[Description of configuration]
The configuration of a communication terminal according to an embodiment of the present invention is shown using the block diagram of FIG.

  Reference numeral 100 denotes the entire communication terminal. The communication terminal 100 has a plurality of communication interfaces, 107 is a first network interface 1, and 108 is a second interface 2. Although the number of interfaces is two in this embodiment, the number of interfaces is not particularly limited to two. Needless to say, the number may be three or more.

  Reference numeral 101 denotes a response time measurement packet generator, which generates a packet for measuring the round-trip response time.

  Reference numeral 102 denotes a transmission source address changing unit that sets one of addresses assigned to the network interface 1 (107) or the network interface 2 (108).

  A clock unit 104 measures the local time of the communication terminal (100).

  Reference numeral 103 denotes a transmission time recording unit, which acquires the time when the response time measurement packet generated in 101 is transmitted from the clock unit (104) and records it in the database shown in 105.

  A network interface selection unit 106 selects a network interface that transmits the response time measurement packet generated in 101.

  Reference numeral 109 denotes a delay measurement unit. When a response time measurement packet is received, a response time measurement packet is transmitted from the difference between the time of the clock unit (104) and the transmission time recorded in the database (105) and then received. Calculate the round trip delay until

[Description of operation]
In order to simplify the description of the operation, it is assumed that IP (Internet Protocol) is used as a network protocol, ping is used as a response time measurement packet, and two wireless LANs are provided as network interfaces. In describing the operation of the present invention, first, the IP format and the ping packet format for response time measurement will be described with reference to FIGS.

  FIG. 3 shows an IPv4 (IP version 4) packet format.

  Basically, it consists of a 20-byte header and an arbitrary length payload. The header includes a 4-byte source IP address and destination IP address.

  FIG. 4 shows an ICMP echo request / echo response packet format.

  An ICMP echo request / echo response shown in FIG. 4 is used in a ping command that is used as a standard for measuring round-trip delay time with a partner on the Internet.

  FIG. 5 shows a packet format when an ICMP packet is transmitted by IPv4.

  FIG. 5 is a diagram in which the payload portion of FIG. 3 is replaced by ICMP of FIG. The present invention is characterized in that the source IP address is changed among the various fields shown in FIG.

  FIG. 2 shows a specific configuration example of the present invention.

  Reference numeral 200 denotes an entire communication terminal, which corresponds to 100 in FIG.

  Reference numeral 207 denotes the first wireless LAN interface 1, which has an IP address 133.204.15.19.

  Reference numeral 208 denotes a second wireless LAN interface, which has an IP address 162.3.45.72.

  Reference numeral 201 denotes a ping packet generation process, which generates a special packet for response time measurement shown in FIG.

  202 is a transmission source IP address changing process, and the transmission source IP address shown in FIG. 5 is changed to the IP address 133.204.15.19 of the wireless interface 1 (207) or the IP address 162.15 of the wireless LAN interface (208). 3. It has a function to set one of 45.72.

  Reference numerals 203, 204, and 205 denote a transmission time recording process, a clock, and a database, which respectively correspond to 103, 104, and 105 in FIG.

  An IP protocol stack 206 has a function of bundling two wireless LAN interfaces (207) and (208). Reference numeral 211 denotes a partner to which the communication terminal transmits a ping packet, which is connected via the Internet (210).

  FIG. 6 is a configuration diagram schematically showing FIG. 2 from the viewpoint of network connection.

  The terminal 1 in FIG. 6 has two interfaces (IF1) and (IF2), and each is connected to the Internet. The terminal 2 in FIG. 6 has one interface (IF) and is connected to the Internet.

  When the packet is transmitted from IF1 of the terminal 1 to the terminal 2, the packet is transmitted / received using the path A of FIG. 6 and when the packet transmitted from the terminal 2 is received by the IF1 of the terminal 1, the path B is similarly transmitted using the IF2. The route of time is route C and route D, respectively, and there are four routes for transmission and reception.

  FIG. 7 shows a ping packet transmission sequence for measuring the delay times of route A, route B, route C, and route D in FIG.

Four types of ping packets are transmitted in order to measure the delay time of all the paths independently.
The first ping packet is
Source address = IF1 (133.204.15.19)
Destination address = Terminal 2 (26.101.66.6244)
Transmission IF = IF1
Send with the setting.

Since the source address of this packet is IF1, the response from the terminal 2 is received by IF1. Therefore, route A is used when this packet is transmitted, and route B is used when it is received. What can be measured with a ping packet is the round-trip response time, so with the first ping packet,
Route A + Route B = Time a (Formula 1)
This means that the total time of the route A and the route B as shown in Equation 1 can be measured.

Similarly, Formula 2, Formula 3, and Formula 4 can be obtained by transmitting the following ping packet.
Second ping packet:
Source address = IF2 (163.3.45.72)
Destination address = Terminal 2 (26.101.66.6244)
Transmission IF = IF1
To route A + route D = time b (Equation 2)
Third ping packet:
Source address = IF2 (163.3.45.72)
Destination address = Terminal 2 (26.101.66.6244)
Transmission IF = IF2
To route C + route D = time c (Equation 3)
Fourth ping packet:
Source address = IF1 (133.204.15.19)
Destination address = Terminal 2 (26.101.66.6244)
Transmission IF = IF2
To route C + route B = time d (Equation 4)
The time difference between the route A and the route C and the time difference between the route B and the route D can be calculated and calculated using the equations 1 to 4.

That is,
Route C-Route A = Time c-Time b (Formula 5)
Or route C-route A = time d-time a (Formula 6)
Route D-Route B = Time b-Time a (Formula 7)
Or route D-route B = time c-time d (Equation 8)
It can obtain | require by each above formula.

  Note that the values of Equation 5 and Equation 6, and the values of Equation 7 and Equation 8 should be the same theoretically because they calculate the time difference of the same route, but actually the time measured by ping varies. The result is not the same. Therefore, the measurement accuracy can be improved by setting the average of Expression 5 and Expression 6 as Path C-Path A.

  FIG. 8 shows a flowchart when a ping packet is transmitted in the sequence shown in FIG.

  If the process is started (step 801 in FIG. 8), a timer for delay time measurement is started in step 802. Next, in step 803, a ping packet whose transmission source address is set to IF1 (133.204.15.19) is transmitted from the interface IF1.

  In step 804, a response from the communication partner is awaited, and when it is received, in step 805, a round-trip delay time is calculated from the difference between the transmission start time and the reception time.

  Steps 807 to 809 are basically the same as steps 802 to 805 surrounded by a broken line 806 except that the setting of the source address corresponding to step 803 and the specification of the interface used for transmission are different. is there.

  These are performed, and the process ends (step 810).

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

  The present embodiment is an embodiment that operates as if there are virtually two network interfaces by using one physical wireless LAN interface in a time-sharing manner, and the configuration is the above-described first embodiment. Therefore, only the difference in operation will be described.

  Reference numeral 910 denotes one physical wireless LAN interface, and it is shown that virtual interface 1 (907) and virtual interface 2 (908) exist by switching APs by time division AP (Access Point) switching processing. .

  Reference numerals 911 and 912 denote wireless LAN APs (Access Points) each having a different SSID (Service Set ID: ID for identifying an access point). By changing the desired connection destination SSID set in the wireless LAN interface (910), the belonging AP can be changed. Note that the function of changing the connection destination access point based on the SSID is a standard function in IEEE 802.11, and a detailed description thereof will be omitted.

  FIG. 10 shows a sequence in the embodiment of FIG.

  FIG. 9 is basically the same flow as FIG. However, since there is only one physical interface, it is necessary to switch the access point immediately after transmitting the transmission source change ping. Therefore, the operation condition of the present embodiment is that the switching is completed before a response is returned from the terminal 2.

  As described above, according to the present invention, the path delay difference when a communication terminal having a plurality of network interfaces performs a handover, the transmission delay difference to the communication partner and the reception delay difference from the communication partner are separately set. It becomes possible to measure.

It is a block diagram which shows the communication terminal of 1st embodiment of this invention. It is a block diagram which shows the specific example of 1st embodiment of this invention. It is a figure which shows the packet format of IPv4. It is a figure which shows the packet format of an ICMP echo request / echo response. It is a figure which shows the packet format of IPv4 + ICMP echo. It is a network path | route conceptual diagram of 1st embodiment of this invention. It is a sequence diagram of a first embodiment of the present invention. It is a figure which shows the flowchart of 1st embodiment of this invention. It is a block diagram which shows the communication terminal of 2nd embodiment of this invention. It is a sequence diagram of a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Communication terminal 101 Response time measurement packet generation part 102 Transmission source address change part 103 Transmission time recording part 104 Clock part 105 Database 106 Network interface selection part 107 Network interface 1
108 Network interface 2
109 Delay measurement unit

Claims (10)

A function having a plurality of network interfaces, assigning a different address to each network interface, a function capable of selecting a network interface to be used in packet transmission, and a response time measurement packet for measuring a path delay with a communication partner In a data packet terminal having a function of generating and a function of measuring a time difference between transmission and reception of the response time measurement packet,
By setting any one address of the network interface as a transmission source address of the response time measurement packet, a transmission path when the response time measurement packet is transmitted to the communication partner and the response time measurement packet from the communication partner A path delay difference measuring method, wherein a round trip delay time is measured by independently specifying a receiving path when receiving a response to a response.   2. The path delay difference measuring method according to claim 1, wherein two response time measurement packets are transmitted from the same network interface, one sets the address of the network interface used for transmission as a source address, One is a method for measuring a path delay difference, wherein an address of a network interface different from the network interface used for transmission is set.   3. The path delay difference measuring method according to claim 2, wherein a one-way delay time difference when a packet is transmitted from the communication partner to the data packet terminal is calculated from a delay time difference between the two response time measurement packets. The path delay measuring method characterized by this.   2. The path delay measuring method according to claim 1, wherein one response time measurement packet is transmitted from each of two different network interfaces, and one of the addresses of the network interface is used as a source address of the two response time measurement packets. A path delay difference measuring method, characterized in that   5. The path delay difference measuring method according to claim 4, wherein a one-way delay time difference when a packet is transmitted from the data packet terminal toward the communication partner is calculated from a delay time difference between the two response time measurement packets. A path delay difference measuring method characterized by:   2. The path delay difference measuring method according to claim 1, wherein each of the plurality of network interfaces has an individual physical interface, and the plurality of network interfaces can be used simultaneously.   2. The path delay difference measuring method according to claim 1, wherein one physical interface is used in a time division manner as a plurality of network interfaces.   2. The path delay difference measuring method according to claim 1, wherein an IP (Internet Protocol) ICMP (Internet Control Message Protocol) packet is used as the response time measuring packet.   A data packet terminal in a communication system, comprising at least one path delay difference measuring method according to any one of claims 1 to 8.   10. The data packet terminal according to claim 9, wherein the data packet terminal has at least one of a wireless interface to a mobile communication network, a wireless LAN interface, or another wireless interface as a network interface.

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