JP2007036601A - Telephone system and its propagation delay measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a telephone system in which fault recovery time is shortened, by making it possible to readily specify faulty portion. <P>SOLUTION: A node field, capable of recording additionally by a routing node, is defined in an RTCP message transferred between end points during telephone conversation of an IP telephone set. Transmission time, processing delay time and receiving time of an RTCP packet at the routing node are recorded in that node field, together with the host name of that node and then the RTCP packets are transferred sequentially. A telephone terminal at the end point acquires information recorded in the node field of a received RTCP packet and measures the propagation delay time required for each span between the routing nodes of the received RTCP packet. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a telephone system that performs voice communication between terminals using IP (Internet Protocol), and a method for measuring propagation delay in this system.

A system for communicating voice information via an IP (Internet Protocol) network is known. This type of system is called an IP telephone system or VoIP (Voice over IP) and has been rapidly spreading in recent years. Since the IP network is a best effort type, it is important to ensure stable communication quality in real-time communication such as voice. For example, Patent Literature 1 discloses a technique for that purpose.
JP 2002-271392 A

By the way, in the existing technology, when voice quality is deteriorated due to a failure or an unstable operation, there is not sufficiently provided a means for determining which part of the IP network has the cause. For this reason, it often takes time to identify and recover from a failure location, and some countermeasure is desired.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a telephone system and a propagation delay measuring method that enable easy identification of a location where an abnormality has occurred, thereby shortening the failure recovery time. is there.

  In order to achieve the above object, according to one aspect of the present invention, in a telephone system in which a plurality of telephone terminals implement a voice call using RTCP via an IP network formed by connecting a plurality of node devices. In the RTCP packet exchanged between telephone terminals connected end-to-end, a node field that can be used by the plurality of nodes is defined, and the node device transfers the RTCP packet to a destination endpoint. A means for recording the transmission time, processing delay time, and reception time of the RTCP packet in the node field each time the telephone terminal obtains information recorded in the node field of the received RTCP packet The propagation delay time required for each span between nodes through which the received RTCP packet passes is calculated. Telephone system comprising means for are provided.

  By taking such measures, a field for a node is defined in an RTCP packet transmitted and received during voice communication between endpoints of telephone terminals that provide a VoIP service. Each time an RTCP packet passes through a node device, a transmission processing delay time and a packet transmission / reception time are added to this field. As a result, the propagation delay time required in the span between the nodes can be measured on each end point, and the location where the failure occurs can be easily identified.

  According to the present invention, it is possible to easily identify a location where an abnormality has occurred, thereby providing a telephone system and a propagation delay measuring method that can shorten the failure recovery time.

  FIG. 1 is a system diagram showing an embodiment of a telephone system according to the present invention. In the figure, a plurality of IP telephones 11 to 16 are accommodated in an IP network formed by nodes 1 to 4. The IP telephones 11 and 12 are accommodated in the node 1, the IP telephones 13 and 14 are accommodated in the node 2, and the IP telephones 15 and 16 are accommodated in the node 3, both via a LAN (Local Area Network). Further, the nodes 1 to 3 are accommodated in the node 4 via the LAN. The nodes 1 to 4 are realized as routers or layer 3 switches, for example. In particular, the node 4 collects the nodes 1, 2 and 3 to enable interconnection. That is, the system of FIG. 1 is a system that realizes a mutual call between the IP telephones 11 to 16 using the VoIP technology with the IP network as a core.

  FIG. 2 is a message sequence diagram exchanged between a telephone terminal connected end-to-end (peer-to-peer) in the system of FIG. 1 and a node therebetween. In FIG. 3, it is assumed that the IP telephone 11 (Tel 11 in the figure) and the IP telephone 13 (Tel 13 in the figure) are connected. In FIG. 2, T-t1s indicates a time at which an RTCP message (SR: Sender Report) is transmitted from Tel11. T-n1r1 is a message reception time at the node 1, Δn11 is a time taken from receiving the message inside the node 1 to transmitting it to the next node, and T-n1s1 is a message from the node 1 to the node 4. Indicates the transmission time. These times are all measured by an NTP (Network Time Protocol) time frame.

  In this embodiment, the message reception time, the time required for processing inside the apparatus, and the message transmission time are additionally recorded in the RTCP message together with the own node host name in each node. Similarly, the reception time, processing time, and transmission time of the RTCP message transmitted from the node 1 to the node 4 are additionally recorded together with the host name of the node 4. The same information is additionally recorded in the node 2, and finally the RTCP message reaches the IP telephone 13 (Tel13). The format of the RTCP message at this point is shown in FIG.

  As shown in FIG. 3, the RTCP message has fields for recording the message transmission time of Tel11, the message reception time of Tel13, and the message residence time of Tel13 based on RFC1889. In addition to this, an additional recording field is provided in this embodiment, and four items of (host name), (message reception time), (message transmission time), and (message residence time) are recorded for each node. . As shown in FIG. 3, the above four items are recorded for each of the nodes 1, 4 and 2. For the sake of convenience, each time and time is indicated with a subscript “1” indicating the forward path. For example, at message reception time T-n4r1 of node 4, n4 indicates node 4, r indicates reception, and the next 1 indicates the forward path.

  Further, the same processing is performed for an RTCP message (SR: Sender Report) returned from Tel13, which is one end of peer-to-peer, toward Tel11. FIG. 4 shows the format of an RTCP message returned from Tel 13 and reaching Tel 11. In the format shown in FIG. 4, in addition to each information on the forward path copied in Tel 13 (the same contents as FIG. 3, subscript 1), (host name), (message reception time), (message transmission time) in the return path, And four items of (message dwell time) are recorded. As described above, in this embodiment, in addition to the information recorded at the end-end by RFC1889, the time information at the midway node is also recorded in the RTCP message.

  The IP telephone 11 that has received the message of FIG. 4 acquires information recorded in the node field of the received RTCP packet, and measures the propagation delay time required for each span between the nodes through which the received RTCP packet has passed. It has a function. That is, the IP telephone at each end point can calculate the propagation delay time within each node and between nodes by the following mathematical formula.

Propagation delay time between Tel13 and node 2 = (T−n2r2) − (T−n2s1) −Δt3 (1)
Propagation delay time between node 4 and node 2 = (T−n4r2) − (Tn4s1) −Δn21−Δn22 − {(Tn2r2) − (Tn2s1)} (2)
Propagation delay time between node 1 and node 4 = (T−n1r2) − (Tn1s1) −Δn41−Δn42 − {(Tn4r2) − (Tn4s1)} (3)
Propagation delay time between Tel11 and node 1 = (T−t1r) − (T−t1s) −Δn11−Δn12 − {(T−n1r2) − (T−n1s1)} (4)
Message residence time in node 2 = Δn21 + Δn22 (5)
Message residence time in the node 4 = Δn41 + Δn42 (6)
Message residence time in node 1 = Δn11 + Δn12 (7)
Furthermore, since the message defined in RFC1889 is used as it is, the propagation delay time between the endpoints, that is, between Tel11 to Tel13 can also be calculated by Expression (8).

Propagation delay time between Tel11 to Tel13 = (T−t1r) − (T−t1s) −Δt3 (8)
As described above, in the present embodiment, the node field that can be additionally recorded by the relay node is defined in the RTCP message exchanged between the endpoints during the IP telephone call. Then, the transmission time, processing delay time, and reception time of the RTCP packet in the transit node are recorded in the node field together with the host name of the node, and the RTCP packet is sequentially transferred. The endpoint telephone terminal acquires information recorded in the node field of the received RTCP packet, and measures the propagation delay time required for each span between the nodes through which the received RTCP packet has passed.

  Since it did in this way, the propagation delay time between each node and the message residence time in a node can be measured in an IP telephone, and when an abnormality occurs in the propagation delay time of an IP packet between endpoints, which route It is possible to easily detect whether or not an abnormality has occurred. Therefore, the failure recovery time can be shortened. There are generally three factors as voice quality degradation factors: increase in jitter, increase in propagation delay, and increase in packet loss. According to the present embodiment, even if the propagation delay increases due to any of the factors, the occurrence point is determined. It becomes possible to specify easily.

  In addition, this invention is not limited to the said embodiment as it is. For example, measurement results may be notified from each end point to a separately provided monitor server and accumulated. In this way, information can be shared, and the propagation delay time between each communication node that passes between each endpoint during voice communication can be determined in real time on the monitor server by not only the terminal user but also the system administrator or the like on the monitor server. It can be observed after the fact.

  Furthermore, the present invention can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

1 is a system diagram showing an embodiment of a telephone system according to the present invention. FIG. 2 is a message sequence diagram exchanged between telephone terminals connected end-to-end in the system of FIG. 1 and nodes between them. The figure which shows the format of the RTCP message which reached | attained the IP telephone set 13 in FIG. The figure which shows the format of the RTCP message which was returned from the IP telephone set 13 and reached the IP telephone set 11.

Explanation of symbols

  1-4 ... node, 11-16 ... IP telephone (Tel)

Claims (2)

In a telephone system in which a plurality of telephone terminals realize a voice call using RTCP (Real Time Control Protocol) via an IP (Internet Protocol) network formed by connecting a plurality of node devices.
A node field that can be used by the plurality of nodes in an RTCP packet exchanged between end-to-end telephone terminals;
The node device comprises means for recording the transmission time, processing delay time, and reception time of the RTCP packet in the node field each time the RTCP packet is transferred to a destination endpoint.
The telephone terminal includes means for acquiring information recorded in a node field of a received RTCP packet and measuring a propagation delay time required for each span between nodes through which the received RTCP packet passes. Phone system. Propagation delay measurement method used in a telephone system in which a plurality of telephone terminals implement a voice call using RTCP (Real Time Control Protocol) via an IP (Internet Protocol) network formed by connecting a plurality of node devices Because
A node field that can be used by the plurality of nodes in an RTCP packet exchanged between end-to-end telephone terminals;
Each time the RTCP packet is transferred to a destination endpoint, the node device records the transmission time, processing delay time, and reception time of the RTCP packet in the node field;
The telephone terminal obtaining information recorded in the node field of the received RTCP packet;
A step of measuring the propagation delay time required for each span between nodes through which the received RTCP packet has passed, by the telephone terminal.

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