JP2003124961A - Equipment for connecting networks with each other, and synchronous communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a high communication quality, with small-scale equipment. SOLUTION: In equipment for connecting networks with each other which so has a plurality of port portions as to connect each network with each port portion, there are provided a synchronous-reference acquiring means and a synchronizing-unit-signal sending-out means. The synchronous-reference acquiring means is so connected with a predetermined input-port portion of the port portions as to acquire a synchronous reference signal from a first network to become the reference of synchronism. The synchronizing-unit-signal sending- out means so generates a predetermined synchronizing unit signal synchronously with the synchronous reference signal acquired by the synchronous-reference acquiring means as to send out the synchronizing unit signal from a predetermined output-port portion connected with a second network.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous communication system, for example, a router having a WAN (Wide Area Network).
LAN (Loca including IP (Internet Protocol) telephone
It is suitable for use in the case where the operation timing of the IP telephone is synchronized with the clock extracted from the WAN by connecting with the l Area Network).

The present invention also relates to an inter-network connection device as a component of such a synchronous communication system.

[0003]

2. Description of the Related Art For example, an IP packet routing device (router) is a device for connecting LANs existing at respective bases to each other through a WAN line. I for WAN line
SDN basic interface, primary group interface, etc. can be connected.

A router is a device for reading the destination information of an IP packet and providing a forwarding function of sending each IP packet from a corresponding port according to the destination information and a routing table installed in advance.

[0005]

[Problems to be Solved by the Invention]
(ce over IP), voice data can be accommodated in an IP packet for voice communication, and an IP telephone (telephone supporting VoIP) can be accommodated in a LAN.
A synchronization problem with the WAN line side occurs.

As a connection form for accommodating an IP telephone in a LAN, a PBX having a function of accommodating an IP telephone
In a LAN including a (private branch exchange), a configuration in which an IP telephone is connected under the control of the PBX, and a configuration in which the IP telephone is directly connected to the LAN (transmission cable for the LAN) without being controlled under the PBX. Can be.

When the IP telephone is subordinate to the PBX, the PBX itself is equipped with a function of sending a synchronization packet (transmitted as a multicast packet) to the IP telephone at a constant cycle. Although synchronization is possible, when an IP telephone is directly connected to a LAN without passing through a PBX, a normal router does not have a function of sending a synchronization packet (usually, the router does not have such a function). (Since no function is required), the synchronization packet cannot be sent itself, and the LAN and WAN interconnected by the router cannot be synchronized.

LAN and W interconnected by a router
The non-synchronization of ANs also causes discards, delays, fluctuations, etc. of IP packets. For communications that require high real-time performance such as voice communications, OSI (Open Syst
ems Interconnection) It is difficult to perform retransmission control etc. that can be performed in the transport layer of the reference model,
This is because when an event that causes a deterioration in communication quality such as discarding, delaying, or fluctuation of an IP packet occurs, the communication quality (quality of conversation voice exchanged between users) is directly deteriorated.

Further, even when connected under the control of the PBX,
When a transmission device such as a router intervenes between the PBX and the IP telephone, the synchronization packet sent from the PBX may be discarded due to congestion in the transmission device. May not be possible.

To deal with this, the IP telephone operates based on the clock generated by itself, or the WAN separately.
It is conceivable that the network is connected to a LAN accommodating an IP telephone so that the synchronization packet output from the network synchronization apparatus can reach the IP telephone by installing a network synchronization apparatus capable of generating a synchronization packet from the WAN line.

However, if the IP telephone generates its own clock, it is possible to send an IP packet containing voice data from the IP telephone, but W
It cannot be synchronized with the AN line side.

When the network synchronization device is provided,
Although it is possible to synchronize with the WAN line side, providing the network synchronizer itself is not preferable because it increases the equipment scale.

[0013]

In order to solve such a problem, according to the first invention, in an inter-network connecting device having a plurality of port units and connecting each network to each port unit, among the port units, , A synchronization reference acquisition unit that is connected to a predetermined input port unit and that acquires a synchronization reference signal from a first network that serves as a synchronization reference, and a predetermined synchronization reference signal that matches the synchronization reference signal acquired by the synchronization reference acquisition unit. It is characterized by further comprising: a synchronization unit signal transmission means for generating a unit signal and transmitting the synchronization unit signal from a predetermined output port connected to the second network.

According to the second aspect of the invention, in an inter-network connection device having a plurality of port units and connecting each network to each port unit, a predetermined input port unit of the port units is connected to perform synchronization. Synchronization reference acquisition means for acquiring a synchronization reference signal from the first network serving as a reference;
And a transmission timing control means for controlling the transmission timing of the unit signal transmitted from a predetermined output port connected to the second network in accordance with the synchronization reference signal acquired by the synchronization reference acquisition means. And

Further, in the synchronous communication system according to the third aspect of the present invention, the inter-network connecting device according to claim 1 and the reception timing of the unit signal transmitted from the inter-network connecting device or the synchronizing unit signal is used. And a synchronized communication device that synchronizes its own operation with the synchronization reference signal.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION (A) Embodiment Hereinafter, an embodiment will be described by taking as an example the case where an inter-network connecting device and a synchronous communication system according to the present invention are applied to an IP network.

(A-1) Configuration of First Embodiment FIG. 1 shows a configuration example of a main part of an IP network 10 which is a LAN of the present embodiment.

In FIG. 1, the IP network 10
Includes an IP telephone 11, a node 12, and a router 13.

Of these, the IP telephone 11 is a telephone having a function of internally generating a synchronization clock CK2 by receiving the synchronization packet SP and the like, and performing a synchronous operation in accordance with the synchronization clock CK2, and is compatible with VoIP. Voice communication. The IP telephone 11 is a transmission cable C forming a transmission line of the IP network 10 which is a LAN.
It is connected to B and receives the synchronization packet SP via the transmission cable CB.

When the transmission cable CB is a coaxial cable, the connection between the IP telephone 11 and the transmission cable CB is performed by making a hole in the cable and bringing the cable pulled out from the IP telephone 11 into contact with the core wire.
In the case of a P (unshielded twisted pair) cable or the like, directly connect the port PT1 on the router 13 side and the port PT11 on the IP telephone 11 side with the UTP cable, or connect it via a concentrator such as a hub. It is done by doing. In any case,
All the components other than the WAN line shown in are one L
Since it belongs to the AN, it can be connected to other nodes 12 and I in the LAN.
It can be said that the P telephone 11 is substantially connected by one bus. That is, the IP network 10 constitutes one collision domain.

Here, the node 12 may be an IP telephone similar to the IP telephone 11, a personal computer equipped with a mailer or a Web browser, a hub, a switching hub, a bridge or the like. Good. Also, if necessary, the node 12 may be a router for interconnection with another LAN. Transmission cable CB
In this way, in addition to the IP telephone 11, one or a plurality of nodes can be connected.

Router 1 for outputting the synchronization packet SP
3 includes a routing function unit 14, a WAN interface unit 15, a clock synchronization unit 16, and a synchronization packet transmission unit 17.

Of these, the WAN interface section 15 connected to the WAN line via the port PT2 is a section for generating the AMI code waveform S1 of 64 kHz + 8 kHz from the reception transmission clock WS. Here, the reception transmission clock WS need not be a special signal but a transmission signal transmitted through the WAN line. Also, 64 kHz + 8 kHz
The AMI code waveform of z is a general clock transmission signal and is a multiplexed signal of a clock having a frequency of 64 kHz and a clock having a frequency of 8 kHz.

The clock synchronization section 16 extracts the 8 kHz clock signal from the 64 kHz + 8 kHz code waveform S1 generated by the WAN interface section 15 and outputs the internal 8 kHz signal.
Phase comparison with the Hz clock CK1 and internal 8 kHz
8k phase of clock CK1 extracted from code waveform S1
This is the part that is synchronized with the Hz clock signal. Synchronized 8
The kHz clock CK1 is supplied to the synchronous packet sending unit 17 as the clock signal S2.

The synchronous packet transmitter 17 which receives the 8 kHz clock signal S2 is a part which counts the received 8 kHz clock signal S2 for a certain period and periodically transmits the synchronous packet SP to the IP telephone 11. Here, the synchronization packet is an IP packet having a specific bit pattern dedicated to synchronization. Further, it is necessary to synchronize with the reception transmission clock WS on the WAN line.
Not only the P telephone 11 but also the node 12 needs to be synchronized when the node 12 is an IP telephone or the like. Therefore, generally, the synchronization packet SP needs to be unspecified or transmitted to a plurality of nodes. .

The node that needs the synchronization packet SP is I
If it exists only in the P network 10, it may be broadcast, but since the broadcast cannot be transmitted beyond the router, if the node 12 is a router, it is possible to reach each node under the node 12 (not shown). To deliver the synchronization packet SP, it is necessary to use multicast. As a result, when there is an IP telephone similar to the IP telephone 11 under the control of the node 12 as a router, the IP telephone can be synchronized using the synchronization packet SP, which is efficient.

Of course, if necessary, the node 12 as a router also has the same configuration as the router 13 (however, W
By replacing the AN interface unit 15 with the LAN interface unit), a new synchronization packet is generated based on the synchronization packet SP transmitted by the router 13 and received by the router 12, and transmitted to a subordinate node (IP telephone or the like). You may do it.

The synchronization packet SP is the synchronization packet transmission unit 1
7 may be directly sent to the transmission cable CB via the port PT3, or the signal S from the synchronous packet sending unit 17 may be sent.
After being sent to the routing function unit 14 as No. 3, it may be sent from the routing function unit 14 to the transmission cable CB.

However, when sending directly from the port PT3 to the transmission cable CB, an IP packet (for example, I packet) sent from the port PT1 to the transmission cable CB.
It is necessary to consider so as not to collide with a packet DP containing voice data for P telephone.

For example, the IP sent from the port PT1
The transmission timings of the packet DP and the IP packet (synchronization packet SP) transmitted from the port PT3 are made different, or the transmission cable C connected to the port PT1
By connecting a transmission cable separate from B to the port PT3, the collision can be prevented.

The routing function unit 14 using the port PT1 reads the destination information of the input IP packet (DP or SP), and according to the destination information and the routing table installed in the routing function unit 14 in advance. A portion having a forwarding function for sending each IP packet from a corresponding port, and usually equipped with a buffer for storing a forwarding queue.
The IP packet input to the routing function unit 14 is
Some are input as the signal S4 via the port PT2 and WAN interface unit 15, and some are input from the port PT1 via the transmission cable CB.

In FIG. 1, a port P for transmitting a synchronous packet is used.
Except for T3, only one port (PT1, PT2) is provided on the WAN side and one on the LAN side,
It is natural that these can be plural as long as they are routers, if necessary.

The operation of this embodiment having the above-mentioned structure will be described below.

(A-2) Operation of the First Embodiment In the IP network 10 of this embodiment, the WAN interface section 15 in the router 13 receives 64 kHz + 8 kHz based on the reception transmission clock WS received from the WAN line.
The z-code waveform S1 is obtained, and the clock synchronization unit 16 that receives the 64 kHz + 8 kHz code waveform S1 extracts the 8 kHz clock signal and synchronizes the phase of the internal 8 kHz clock CK1 with the 8 kHz clock signal.

Synchronized 8 kHz clock CK1
Is supplied to the synchronous packet transmitter 17 as the clock signal S2.

When the synchronous packet transmitter 17 transmits the synchronous packet SP from the port PT1, the synchronous packet SP is supplied to the routing function unit 14 as a signal S3 and then input from the WAN line via the port PT2. The synchronous packet SP is sent to the transmission cable CB together with the IP packet DP.

By the way, starting from port PT2, W
When congestion occurs in the internal route for processing the IP packet DP reaching the routing function unit 14 via the AN interface unit 15, the IP packet DP is discarded due to overflow of the buffer mounted in the routing function unit 14. Can be lost in
Unlike the IP packet DP, the synchronous packet SP of the present embodiment is supplied through the internal path from the synchronous packet sending unit 17 to the routing function unit 14, and therefore, even when the congestion occurs, the synchronous packet SP is not included in the synchronous packet SP. It is possible to prevent packet discard.

For example, the IP packet DP and the synchronization packet SP may be stored in different buffers and the processing of the synchronization packet SP may be preferentially executed.

As a result, even when there is congestion such that the IP packet DP is dropped, the synchronous packet DP is not dropped. Therefore, the IP telephone 1
1 can reliably receive the synchronization packet SP via the transmission cable CB, and can synchronize.

When such a configuration is adopted, the bandwidth is consumed for transmitting the synchronization packet SP and the bandwidth that can be used for transmitting the IP packet DP is limited, but the port PT1 to the transmission cable CB is limited. IP packet DP
If the synchronized clock signal S2 is reflected in the transmission timing itself of, the dedicated synchronization packet SP need not be transmitted for synchronization.

That is, even if the destination is not the IP telephone 11, the IP packet DP is transmitted on the transmission cable CB connected to the port PT11 of the IP telephone 11, so that the IP telephone 11 receives the IP packet DP. The IP packet DP can be physically received regardless of whether it is addressed to itself, and desired synchronization can be achieved based on the reception timing.

In particular, at the time of congestion, it is necessary to quickly reduce the congestion level by using as wide a band as possible for transmitting the IP packet DP. Therefore, instead of the synchronization packet DP, the IP packet DP The method of synchronizing at the transmission timing is efficient.

(A-3) Effects of the First Embodiment According to the present embodiment, the WAN line and the IP telephone in the LAN can be synchronized only by arranging the router (13). It is possible to obtain high communication quality with various facilities.

(B) Second Embodiment Hereinafter, only differences of the present embodiment from the first embodiment will be described.

In the present embodiment, it is possible to add or delete the functions (the synchronization packet sending unit 17 and the clock synchronization unit 16) necessary for synchronization according to the communication device arranged in the LAN. By making it possible, it is characterized in that it is more flexible than in the first embodiment.

As described above, the router normally does not need to have the function of synchronizing the WAN line and the communication device under it, so that it does not need to have the function of sending the synchronization packet, but the IP telephone set to the LAN under control. If a communication device that requires high real-time property such as is provided, it is necessary. Therefore, it is preferable that the function of the router can be flexibly changed according to the configuration of the subordinate LAN.

(B-1) Configuration and Operation of Second Embodiment FIG. 2 shows a configuration example of the main part of the IP network 20 which is the LAN of the present embodiment.

In FIG. 2, the function of each component and each signal given the same reference numeral as in FIG. 1 is the same as that of the first embodiment.

Therefore, in the present embodiment, the synchronization unit 22 equipped with the synchronization packet transmission unit 17 and the clock synchronization unit 16 is detachably attached (or connected) to the router 21. Is different from.

Here, the router 21 is provided with only the routing function unit 14 which is the minimum function required for the router connected to the normal WAN line, and the WAN interface unit 15.

Of course, the router 21 and the synchronization unit 22
Is attachable / detachable, the synchronization packet sending unit 17 is connected to the routing function unit 14 and the clock synchronizing unit 16 is connected to the WAN interface unit 15 when the device is attached.
Must be connected to have the same function as the router 13 of the first embodiment.

On the contrary, since there is no communication device having a high real-time property in the IP network 20, the synchronization unit 22
When it is unnecessary, the synchronization unit 22 can be removed and the router 21 can be used alone.

Structure of the IP network 20, that is,
Since the number and types of communication devices arranged on the LAN as the IP network 20 can be dynamically changed according to the needs of the user, the IP phones (for example, 11) that have been arranged until then are deleted. It is possible that an IP telephone (for example, 11) that has not been placed until then is added. The IP telephone (for example, 11) that had been placed until then is deleted and
(If 2 is a router, the LAN under the node 12 is also included.) If there is no communication device having a high real-time property at all, the synchronization unit 22 becomes unnecessary and can be deleted. When a communication device having a high real-time property such as an IP telephone (for example, 11) that has not existed is added, the synchronization unit 22 that did not exist until then can be additionally connected.

(B-2) Effect of Second Embodiment According to this embodiment, it is possible to obtain the same effect as that of the first embodiment.

In addition, in the present embodiment, it is possible to dynamically delete or add the synchronization unit according to the change of the communication device arranged in the LAN (IP network 20), and it is excellent in flexibility.

(C) Other Embodiments The router has been described in the first and second embodiments, but the present invention is directed to the layer 3 having the WAN interface section.
It is also applicable to IP packet communication devices such as switches.

In the first and second embodiments, the IP
Although the telephone has been described as an example, the IP telephone can be replaced with another communication device that requires high real-time property.

Further, in the first and second embodiments, the number of nodes 11 and 12 connected to the transmission cable CB is two.
However, this may be one or three or more as required.

In the above description, although it was realized mainly by hardware, the present invention can also be realized by software.

[0060]

As described above, according to the present invention, the second network side can be synchronized with the synchronization reference signal obtained from the first network only by using the inter-network connecting device. Therefore, it is possible to obtain high communication quality with a small-scale facility.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a main part of an IP network according to a first embodiment.

FIG. 2 is a schematic diagram showing a configuration example of a main part of an IP network according to a second embodiment.

[Explanation of symbols]

10, 20 ... IP network, 11 ... IP telephone, 1
3 ... Router, 14 ... Routing function unit, 15 ... WAN
Interface section, 16 ... Clock synchronizing section, 17 ... Synchronous packet sending section, PT1 to PT3, PT11 ... Port,
SP ... Sync packet.

Claims (3)

[Claims] 1. An inter-network connection device comprising a plurality of port units and connecting each network to each port unit, wherein the first unit is a reference for synchronization, which is connected to a predetermined input port unit of the port units. A synchronization reference acquisition unit that acquires a synchronization reference signal from a network, and a predetermined synchronization unit signal that is generated in accordance with the synchronization reference signal acquired by the synchronization reference acquisition unit, and that synchronization unit signal is connected to a second network. And a synchronization unit signal transmitting means for transmitting from the predetermined output port section. 2. An inter-network connection device comprising a plurality of port units and connecting each network to each port unit, wherein a first input unit that is connected to a predetermined input port unit among the port units and serves as a reference for synchronization. The synchronization reference acquisition means for acquiring the synchronization reference signal from the network and the transmission timing of the unit signal transmitted from the predetermined output port connected to the second network are matched with the synchronization reference signal acquired by the synchronization reference acquisition means. An inter-network connection device comprising: a transmission timing control means for controlling the transmission. 3. The inter-network connection device according to claim 1 or 2, and the reception timing of a unit signal transmitted from the inter-network connection device, or a unit signal for synchronization, which is used for the operation of the synchronization reference signal. A synchronized communication system comprising: