Packet communication system

The present invention relates to a packet communication system technology, and more particularly to a technology for performing synchronous communication in a packet communication system in which a plurality of terminal-side communication devices are connected to one station-side communication device by a network that performs packet communication.

Non-Patent Document 1 and Non-Patent Document 2 have proposed a conventional technique for transferring TDM (Time Division Multiplexing) communication on a packet network.

This conventional technology is a method of transferring TDM data by an asynchronous packet network such as IP (Internet Protocol), MPLS (Multi Protocol Label Switching) or Ethernet (registered trademark) specified in IEEE802.3.

However, in the conventional technology, as shown in FIG. 7, a system configuration in which two devices (first conventional communication device 111 and second conventional communication device 112) perform synchronous communication via the packet network 113 is used. It is a technology applied to. Therefore, the first conventional communication device 111 and the second conventional communication device 112 perform unicast communication with each other using IP packets destined for each other's IP addresses. In the figure, 114 and 115 are TDM lines connected to the first conventional communication device 111 and the second conventional communication device 112, respectively.

Therefore, for example, as shown in FIG. 8, one conventional communication device (third conventional communication device 123) becomes two conventional communication devices (first conventional communication device 121 and second conventional communication device 123). When connected to the communication device 122) of the above, for example, the first TDM line 125 housed in the first conventional communication device 121 is housed in the third conventional communication device 123. The second TDM line 126 and the third TDM line 127, which are connected to the fourth TDM line 128 and housed in the second conventional communication device 122, are housed in the third conventional communication device 123. When connected to the fifth TDM line 129 and the sixth TDM line 130, the third conventional communication device 123 receives the data received from the fourth TDM line 128 from the first conventional communication device 123. The data received from the fifth TDM line 129 and the sixth TDM line 130 is mounted on the IP packet addressed to the second conventional communication device 122. Had to be sent.

As described above, in the conventional technology, since unicast communication is used, when one conventional communication device is connected to a plurality of conventional communication devices, a plurality of packets destined for each are used. Needed to be transferred individually. Therefore, there is a problem that the efficiency of packet transfer is poor.

For example, in the configuration shown in FIG. 8, a case where TDM data is mounted on an Ethernet (registered trademark) packet and transferred at a cycle of 8 kHz will be described. If each TDM line has a transmission capacity of 64 kb / s, the amount of data received from each TDM line every 8 kHz is 8 bits (= 1 byte).

Since the shortest packet length of Ethernet (registered trademark) is 64 bytes, in the conventional technology, 1 byte of TDM data is applied from the third conventional communication device 123 to the first conventional communication device 121 in an 8 kHz cycle. A 64-byte Ethernet (registered trademark) packet equipped with the above was transferred, and similarly, a 2-byte TDM data was loaded from the third conventional communication device 123 to the second conventional communication device 122 at an 8 kHz cycle. A 64-byte Ethernet® packet will be forwarded. Therefore, in order to transfer data for three TDM lines with a transmission capacity of 64 kb / s over Ethernet (registered trademark), the transmission capacity of approximately 8.2 Mb / s (= 8 kHz x 64 bytes x 2 packets) is Ethernet. It will be consumed on (registered trademark).

Here, one conventional communication device (third conventional communication device 123) faces two conventional communication devices (first conventional communication device 121 / second conventional communication device 122). In general, when facing each other at 1: N, the bandwidth consumed on the packet network increases in proportion to N. As described above, the conventional technology has a problem that when transferring TDM communication on a packet network in a 1: N connection form, a very large bandwidth is required and the bandwidth usage efficiency is very poor.

In particular, in a service provided by a telecommunications carrier, one station-side communication device is connected to a plurality of terminal-side communication devices via a packet network, so that the bandwidth as described above is used. There was a problem of inefficiency.

<nplcit num="1"><text>S. Bryant et al., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", IETF RFC3985, March 2005 Search, Internet &lt;URL: ftp://ftp.rfc-editor.org/in-notes/rfc3916 .txt&gt;</text></nplcit><nplcit num="2"><text>Y (J) Stein et al., "TDM over IP", IETF Internet-draft draft-ietf-pwe3-tdmoip-04.txt, February 2005 Search, Internet &lt;URL: http: //www.ietf.org/internet -drafts / draft-ietf-pwe3-tdmoip-04.txt&gt;</text></nplcit>

<p> As described above, in the conventional technique, in order to transfer synchronous communication data from one station-side communication device to a plurality of (N) terminal-side communication devices on a packet communication system connected to 1: N. In addition, a large transmission band required in proportion to the number of terminal-side communication devices is required, and there is a problem that the band usage efficiency is poor.</p><p> Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a packet communication system which requires a small amount of bandwidth and can improve the efficiency of bandwidth utilization.</p>

<p> In the present invention, in order to achieve the above object, a multicast communication packet is used to transfer a packet from a station-side communication device to a plurality of terminal-side communication devices, and conversely, one station side from a plurality of terminal-side communication devices. Unicast communication packets are used to transfer packets to the communication device. This makes it possible to solve the conventional problem that a large transmission band required in proportion to the number of terminal-side communication devices is required and the band usage efficiency is poor.</p><p> Hereinafter, the configuration of each claim of the present invention will be described. a) In the invention according to claim 1, a plurality of terminal-side communication devices and one station-side communication device are connected via a network for performing packet communication, and the network is a specific communication device. Unicast communication as a destination and multicast communication with a plurality of communication devices satisfying all or specific conditions are possible, and the terminal-side communication device and the station-side communication device periodically send and receive packets. , A packet communication system that performs clock-synchronized communication between the terminal-side communication device and the station-side communication device, and the station-side communication device is a plurality of the terminal-sides that are destinations of the multicast communication packets. Communication data to be transferred to each communication device is periodically created, multicast communication packets are periodically created using the created communication data, and the multicast communication packets are periodically transmitted to the network. The terminal-side communication device that has received the multicast communication packet is characterized in that the communication data addressed to the own terminal-side communication device is taken out from the multicast communication packet and received. The described invention is characterized in that, in claim 1, the network is any one of Ethernet (registered trademark), IP network, and PON (Passive Optical Network).</p><p>b) In the invention according to claim 3, in claim 1 or 2, the terminal-side communication device is connected to one or more terminals, and communication data is periodically created from signals received from the plurality of terminals. Then, using the created communication data, the unicast communication packet addressed to the station side communication device is periodically created, and the unicast communication packet is periodically transmitted to the network. The invention according to claim 4 is characterized in that, in claim 3, the plurality of terminals are terminals for performing TDM communication or analog terminals.</p><p>c) In the invention according to claim 5, in any one of claims 1 to 4, the terminal-side communication device generates a clock based on the arrival time of the received multicast communication packet, and the station-side communication device. It is characterized by being synchronized with.</p>

<p> According to the present invention, the bandwidth can be efficiently used by using the packet communication system having the above configuration. Further, according to the present invention, it is also possible to perform clock reproduction for TDM transfer on a packet network.</p>

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

&lt;Example 1&gt; Ethernet (registered trademark) network FIG. 1 is a diagram showing a first embodiment of a packet communication system according to the present invention. In this embodiment, one station-side communication device 15 (for example, connected to a station switchboard) and N terminal-side communication devices 11, ..., 12,13, ..., 14 (for example, installed in each home). Is connected by an Ethernet (registered trademark) network specified by IEEE802.3.

In this embodiment, for the sake of simplicity, an Ethernet (registered trademark) network composed of two layer 2 switches (first layer 2 switch 16 / second layer 2 switch 17) is taken as an example. The explanation is given, but as is clear from the following explanation, it does not depend on the number of layer 2 switches.

As shown in FIG. 1, the station-side communication device 15 has one Ethernet (registered trademark) interface connected to the first layer 2 switch 16 and at least one TDM (Time Division Multiplexing) interface. It has (TDM line 22).

In addition, each of the terminal-side communication devices 11, ..., 12, 13, ..., 14 has one Ethernet (registered trademark) interface connected to the layer 2 switch and at least one TDM interface or analog interface. Has (18 ~ 21).

A terminal (not shown) that performs TDM communication such as ISDN (Integrated Services Digital Network) is connected to the TDM interface (TDM line), and a terminal such as an analog telephone (figure) is connected to the analog interface (analog line). (Not shown) is connected, and the analog signal is converted into a TDM communication signal in the terminal-side communication devices 11, ..., 12, 13, ..., 14.

The TDM communication signal of the terminal-side communication device 15 is multiplexed by TDM on the TDM interface (TDM line 22) of the station-side communication device 15, and is connected to, for example, an exchange.

In this embodiment, the station-side communication device 15 and the terminal-side communication device 11, ..., 12,13, ..., 14 are connected by layer 2 switches 16 and 17 via an Ethernet (registered trademark) interface. ..

Ethernet (registered trademark) is destined for unicast communication destined for a MAC address unique to the communicator and a multicast address defined to be received by all connected or multiple communicators satisfying specific conditions. Multicast communication is defined.

Further, as a special form of multicast communication, there is broadcast communication to a broadcast address specified to be received by all communication devices. In the embodiment of the present invention, as is clear from the following description, there is no difference between multicast and broadcast. Therefore, here, these are collectively referred to simply as multicast and the following description will be given.

Further, here, a case where the TDM data transmitted / received by the terminal-side communication devices 11, ..., 12, 13, ..., 14 is set to 64 kb / s and clock synchronization is performed at 8 kHz will be described. Here, communication from the station-side communication device 15 to the terminal-side communication device 11, ..., 12, 13, ..., 14 will be described.

FIG. 9 is a diagram showing a packet format according to the conventional technique described in Non-Patent Document 1, in which a packet header 141 for transferring a packet to a specific communication device and a CESoPSN (CESoPSN) for mounting TDM communication data on the packet. It consists of a header 142 of Circuit Emulation over Packet Switched Networks), TDM communication data 143 to be carried, and padding data 144 for adjusting the packet length. In the conventional technique, the destination address described in the packet header unit 141 is a unique MAC (Media Access Control) address of a specific terminal-side communication device.

In order to perform clock synchronization at 8 kHz, the station-side communication device transmits the packet shown in FIG. 9 to the terminal-side communication device at a cycle of 8000 times per second. In this case, in order to transmit a data amount of 64 kb / s, the TDM communication data 143 of the packet shown in FIG. 9 is 1 byte, and by adding the padding data 144, the packet has the shortest packet length of 64 bytes. ing.

FIG. 2 is a diagram showing a packet format according to the present invention. Ethernet (registered trademark) header 23 for multicast forwarding of packets to multiple communication devices, CESoPSN header 24 for loading TDM communication data in packets, TDM communication data 25 to 27 to be carried, and packet length adjustment. It consists of padding data 28.

In the present invention, the destination address described in the Ethernet (registered trademark) header 23 is a multicast address. Further, since the TDM communication data is the TDM communication data to be transferred to the N terminal side communication devices, as shown in FIG. 2, the TDM communication data 25 addressed to the first terminal side communication device and the second terminal side The TDM communication data 26 to the communication device, ..., and the TDM communication data 27 to the Nth terminal-side communication device are arranged in this order. Here, since each TDM communication data is 1 byte as described above, the TDM communication data is N bytes in total.

Here, in the case of the configuration of the first embodiment of the present invention shown in FIG. 1, the station-side communication device 15 transmits the multicast packet shown in FIG. 2 at a cycle of 8000 times per second. Further, the first layer 2 switch 16 that has received the multicast packet forwards the multicast packet to the terminal-side communication devices 11 to 12 and the second layer 2 switch 17 connected to the first layer 2 switch 16. To do. Further, the second layer 2 switch 17 that has received the multicast packet forwards the multicast to the terminal-side communication devices 13 to 14 connected to the second layer 2 switch 17.

The terminal-side communication devices 11 to 14 that have received the multicast packet extract the TDM communication data to be received by the local terminal-side communication device from the TDM communication data portion of the multicast packet, and use the extracted TDM communication data as the TDM interface (TDM). Output to the line). Further, since the multicast packet arrives at each terminal-side communication device in a cycle of 8 kHz, it is possible for each terminal-side communication device 11 to 14 to reproduce the clock based on the arrival time of the multicast packet.

Here, for example, when the packet length of the multicast packet is 64 bytes, the required bandwidth is about 4 Mb / s (= 64 bytes × 8 kHz) for all the links shown in FIG. On the other hand, in the conventional technology, in order to communicate with each terminal side communication device by the unicast packet shown in FIG. 9, the link between the station side communication device and the first layer 2 switch is about 4 N Mb. It requires a bandwidth of / s, which is N times the bandwidth required by the packet communication system of the present invention.

Further, in the terminal-side communication device, data is periodically extracted from the synchronization signals received from one or a plurality of connected terminals using the reproduced clock. In this embodiment, data is extracted at a cycle of 8 kHz, mounted on a packet, and transmitted to a station-side communication device. The packet transmitted from the terminal-side communication device to the station-side communication device is unicast communication destined for the station-side communication device. This is because this packet only needs to reach the station-side communication device and does not need to reach other terminal-side communication devices.

By performing such an operation, in the packet communication system of the present invention, the required bandwidth is small, and the bandwidth can be used efficiently.

&lt;Example 2&gt; IP network In the first embodiment described above, a case where a multicast packet is used on an Ethernet (registered trademark) network has been described. However, the packet communication system of the present invention is not limited to Ethernet (registered trademark), and can be realized on an IP network.

FIG. 3 is a diagram showing an example of a second embodiment of the packet communication system of the present invention. In this embodiment, the configuration is the same as that of the first embodiment, and one station-side communication device 35 and N terminal-side communication devices 31 to 34 have two routers (first router 36, first router 36, first). It is connected by the second router 37).

FIG. 4 is a diagram showing a multicast packet format in the second embodiment of the present invention.

As shown in the figure, the packet is an IP multicast packet, and the IP header 43 for multicast forwarding of the packet to multiple communication devices, the CESoPSN header 44 for carrying TDM communication data in the IP packet, and the TDM communication to be carried. It consists of data 45 to 47 and padding data 48 for adjusting the packet length.

In the present invention, the destination address described in the IP header 43 is a multicast address. Further, since the TDM communication data is the TDM communication data to be transferred to the N terminal side communication devices, as shown in FIG. 4, the TDM communication data 45 addressed to the first terminal side communication device and the second terminal side The TDM communication data 46 to the communication device, ..., and the TDM communication data 47 to the Nth terminal-side communication device are arranged in this order. Here, since each TDM communication data is 1 byte as described above, the total of TDM communication data 45 to 47 is N bytes.

The station-side communication device 35 periodically transmits such an IP multicast packet, and the routers 36 and 37 send the IP multicast packet in the same manner as the layer 2 switches 16 and 17 (see FIG. 1) of the first embodiment. Forward.

Further, it is possible to reproduce the clock in each of the terminal-side communication devices 31 to 34 by using the IP multicast packet transmitted from the station-side communication device 35 on a regular basis.

Further, the terminal-side communication devices 31 to 34 periodically extract data from the synchronized signals received from one or a plurality of connected terminals using the reproduced clock. In this embodiment, data is extracted at a cycle of 8 kHz, mounted on a packet, and transmitted to the station-side communication device 35.

The packet transmitted from the terminal-side communication devices 31 to 34 to the station-side communication device 35 is IP unicast communication destined for the station-side communication device 35. This is because this packet only needs to reach the station-side communication device 35 and does not need to reach other terminal-side communication devices.

By performing such an operation, the packet communication system of the present invention requires a small amount of bandwidth and can efficiently use the bandwidth as in the first embodiment.

Although the case of the IP header is described here as the packet header, there may be a UDP (User Datagram Protocol) header or an RTP (Real-time Transport Protocol) header between the IP header and the CESoPSN header.

&lt;Example 3&gt; PON type system FIG. 5 is a diagram showing a third embodiment in which the packet communication system according to the present invention is used in the form of PON (Passive Optical Network).

In this embodiment, as shown in the figure, one station-side communication device 52 and N terminal-side communication devices 50 to 51 are GE-PON (Gigabit Ethernet®-Passive) specified by IEEE802.3ah. It is connected via Optical Network). That is, the station-side communication device 52 is connected to one OLT (Optical Line Terminal) 53, and the OLT 53 and N ONUs (Optical Network Units) 1 to N (54 to 55) are branched and coupled in a many-to-one manner. It is connected by a fiber, and terminal-side communication devices 1 to N (50 to 51) are connected to each ONU 54 to 55.

Here, the interface between the station-side communication device 52 and OLT53 and between ONU1 to N (54 to 55) and the terminal-side communication device 1 to N (50 to 51) is Ethernet (registered trademark) specified by IEEE802.3. Suppose it is an interface.

In addition, the station-side communication device 52 and the terminal-side communication devices 1 to N (50 to 51) have TDM interfaces (TDM lines 58 and 56,57), and TDM data using Ethernet (registered trademark) packet communication. Is configured to transfer between the station-side communication device 52 and the terminal-side communication devices 1 to N (50 to 51).

Here, the station-side communication device 52 periodically transmits an Ethernet (registered trademark) multicast packet to the OLT53 side. The packet format is the same as in FIG. 2 shown in the first embodiment of the present invention. Here, it is assumed that the transmission is performed in a cycle of 8 kHz. In this multicast packet, the destination MAC address is multicast, and the source MAC address is the MAC address of the station-side communication device 52.

Upon receiving this multicast packet, the OLT 53 forwards the multicast packet using a logical link that can be received by all ONU1 to N (54 to 55). By performing such an operation, the multicast packet is received by all N connected ONU1 to N (54 to 55).

The ONU1 to N (54 to 55) that have received the multicast packet are forwarded to the terminal-side communication devices 1 to N (50 to 51) via the Ethernet (registered trademark) interface, respectively. The terminal-side communication devices 1 to N (50 to 51) receive the multicast packet and reproduce the clock from the arrival timing.

In this embodiment, the multicast packet arrives at the terminal-side communication device 1 to N (50 to 51) at a cycle of about 8 kHz, excluding the time fluctuation of the processing related to the transfer. Therefore, the terminal-side communication device 1 to It is possible to reproduce an 8kHz clock at N (50 to 51).

Further, unlike the above-mentioned conventional technology, since the multicast packet is used, the required bandwidth is about 4 Mb / s (= 64 bytes × 8 kHz) regardless of the number of ONUs. Compared to the conventional technology that required a transmission band of 131 Mb / s for 32 terminal-side transmission devices, the band can be used efficiently.

Further, each of the terminal-side communication devices 1 to N (50 to 51) periodically extracts data from the synchronized signals received from one or a plurality of connected terminals using the reproduced clock. In this embodiment, data is extracted at a cycle of 8 kHz, mounted on a packet, and transmitted to the station-side communication device 52. The packet transmitted from the terminal-side communication devices 1 to N (50 to 51) to the station-side communication device 52 is unicast communication destined for the MAC address of the station-side communication device 52. This is because this packet only needs to reach the station-side communication device 52 and does not need to reach other terminal-side communication devices.

Here, GE-PON has been described as an example, but as is clear from the above explanation, the packet network connecting the station-side communication device 52 and the terminal-side communication devices 1 to N (50 to 51) is GE-PON. Not limited to. The packet network that connects the station-side communication device 52 and the terminal-side communication devices 1 to N (50 to 51) is an optical access network using B-PON and G-PON specified by ITU-T, and an Ethernet (registered trademark) switch. It may be an Ethernet (registered trademark) network composed of a media converter or an IP network composed of a router or a switch.

In this embodiment, by performing such an operation, as in the first and second embodiments, the required band is small and the band can be used efficiently.

&lt;Example 4&gt; Integrated system FIG. 6 is a diagram showing a fourth embodiment of the packet communication system according to the present invention. In this embodiment, as shown in the figure, the station-side communication device 72 has an OLT (Optical Line Terminal) function of GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network), and the terminal-side communication device 1 A case where ~ N (70 to 71) has an ONU (Optical Network Unit) function of GE-PON will be described.

In this embodiment, one station-side communication device 72 and N terminal-side communication devices 1 to N (70 to 71) are connected via the GE-PON interface specified by IEEE802.3ah. Further, the station side communication device 72 further has an Ethernet (registered trademark) interface 77 and a TDM interface (TDM line) 78, and the terminal side communication devices 1 to N (70 to 71) further have an Ethernet (registered trademark) interface 73. , 75 and TDM interface (TDM line) 74,76.

Here, the station-side communication device 72 periodically transmits an Ethernet (registered trademark) multicast packet to the PON section as in the first embodiment. Here, it is assumed that the transmission is performed in a cycle of 8 kHz. In this multicast packet, the destination MAC address is multicast, the source MAC address is the MAC address of the station side communication device 72, and a logical link that can be received by all terminal side communication devices 1 to N (70 to 71) is used. Forward the multicast packet. By performing such an operation, the multicast packet is received by all the N terminal-side communication devices 1 to N (70 to 71) to which the packet is connected.

The terminal-side communication devices 1 to N (70 to 71) that have received the multicast packet reproduce the clock from the arrival timing. In this embodiment, the multicast packet for clock transfer and the packet for ordinary Ethernet (registered trademark) communication are mixed in the PON section.

If time fluctuations occur due to this mixture, the clock reproduction accuracy of the terminal-side communication devices 1 to N (70 to 71) deteriorates. Therefore, the station-side communication device 72 normally uses the multicast packet for clock transfer. It has a function of giving priority to forwarding packets of Ethernet (registered trademark) communication.

By doing so, the multicast packet arrives at the terminal-side communication devices 1 to N (70 to 71) at a cycle of about 8 kHz, excluding the time fluctuation of the processing related to the transfer. Therefore, the terminal-side communication device It is possible to reproduce an 8kHz clock from 1 to N (70 to 71).

Further, in the terminal-side communication devices 1 to N (70 to 71), data is periodically generated from the synchronization signal received from one or a plurality of connected terminals (not shown) using the reproduced clock. Is extracted. In this embodiment, data is extracted at a cycle of 8 kHz, mounted on a packet, and transmitted to the station-side communication device 72. The packet transmitted from the terminal-side communication devices 1 to N (70 to 71) to the station-side communication device 72 is unicast communication destined for the MAC address of the station-side communication device 72. This is because this packet only needs to reach the station-side communication device 72 and does not need to reach other terminal-side communication devices.

By performing such an operation, the packet communication system of the present invention requires a small amount of bandwidth and can efficiently use the bandwidth as in the first, second, and third embodiments. Is.

<figref num="1">It is a figure which shows the example of the 1st embodiment of the packet communication system which concerns on this invention.</figref><figref num="2">It is a figure which shows the packet format which concerns on this invention.</figref><figref num="3">It is a figure which shows the example of the 2nd Embodiment of the packet communication system which concerns on this invention.</figref><figref num="4">It is a figure which shows the multicast packet format in the 2nd Example which concerns on this invention.</figref><figref num="5">It is a figure which shows the 3rd Example which used the packet communication system which concerns on this invention in the form of PON (Passive Optical Network).</figref><figref num="6">It is a figure which shows the 4th Example of the packet communication system which concerns on this invention.</figref><figref num="7">It is a figure for demonstrating the conventional system configuration in which two devices perform synchronous communication over a packet network.</figref><figref num="8">It is a figure for demonstrating the conventional system configuration in the case where one communication device is connected to two communication devices facing each other.</figref><figref num="9">It is a figure which shows the packet format which concerns on the prior art.</figref>

Code description

11 ~ 14,31 ~ 34,50 ~ 51,70 ~ 71: Terminal side communication device 15,35,52,72: Station side communication device 16: First layer 2 switch 17: Second layer 2 switch 18 ~ 21,38 ~ 41,56 ~ 57,74,76: TDM line or analog line 22,42,58,78: TDM line 23: Ethernet (registered trademark) header 24,44: CESoPSN header 25 ~ 27,45 ~ 47 : TDM communication data addressed to the terminal side communication device of the first to N 28,48: Badting data 36: First router 37: Second router 43: IP header 53: OLT (Optical Line Terminal) 54 to 55: ONU (Optical Network Unit) 59 ~ 61,73,75,77: Ethernet (registered trademark) interface 111,121: First conventional communication device 112,122: Second conventional communication device 113,124: Packet network 114,115: TDM line 123: Third conventional communication device 125 ~ 130: First to sixth TDM lines 141: Packet header 142: CESoPSN header 143: TDM communication data 144: Badting data