WO2006077640A1

WO2006077640A1 - Multicast relay method and device

Info

Publication number: WO2006077640A1
Application number: PCT/JP2005/000680
Authority: WO
Inventors: Mamoru Koshi
Original assignee: Fujitsu Limited
Priority date: 2005-01-20
Filing date: 2005-01-20
Publication date: 2006-07-27

Abstract

Multicast relay method and device obtain a transmission time of first multicast control information from each transmission source, store such a second delay time in a corresponding manner as is the sum of the transmission time and a first delay time contained in the first multicast control information, transmit the longest delay time among in the second delay times, upstream while being contained in second multicast control information, then start the transmission of multicast information to be relayed, from the transmission source corresponding to the longest delay time, and subsequently transmit the multicast information sequentially to each transmission source by delaying the information by a difference between the longest delay time and each of the second delay times.

Description

Specification

Multicast relay method and apparatus

Technical field

TECHNICAL FIELD [0001] The present invention relates to a multicast relay method and apparatus, and more particularly to a multicast relay method and apparatus considering delay.

Background art

[0002] As a method of distributing sender power information to a specific number of recipients, there are multicast communication and multicast communication. Among them, in the case of multicast communication, since a one-to-one communication from a sender to a specific number of recipients, it is necessary for the sender to prepare as many information as the number of recipients. Network resources used in proportion to

On the other hand, in multicast communication, a specific number of recipients are grouped into a multicast group.

It is managed in units called (distribution groups), and one transfer route is set for each multicast group. This forwarding path is set so that all receivers belonging to the multicast group, such as the sender, are connected. Recipients can receive information distribution services by joining a multicast group. Since the transfer route changes depending on the recipient's participation status, it is necessary to update the route information as needed.

[0004] In general, in multicast communication, a transfer path has a tree structure with a sender as a starting point and a receiver as an end point. Transmitter power The relay device that becomes a branch point to the receiver relays information to the transmission path where the participating group exists. If two or more transmission paths are provided and each requires relaying, information is copied in the relay equipment and relayed to each transmission path. By repeating this, information is distributed to the recipient.

[0005] Therefore, unlike multicast communication, in multicast communication, a relay device that does not need to prepare as many information as the number of receivers duplicates information as necessary. Compared to the case of cast communication, network resources will be used more efficiently.

[0006] Hereinafter, an outline of general multicast communication will be described with reference to FIG. 5 and FIG. Fig 5 These show a configuration example of a simple multicast communication system. Shown via server S1 that is the sender of information for multicast group G1 and client C1 that is the receiver that receives information from server S1 by requesting participation in multicast group G1 and power relay device R1-R6 Are connected in a tree shape.

[0007] It should be noted that the relay device R1 is generally called a first hop router, and in the example of the figure, the server S1 is not connected upstream of the relay device R1, but usually a plurality of servers are connected. Is. The relay device R2 is generally called a rendezvous point or a shared tree router.

[0008] Assume now that server S1 distributes multicast information 200 of multicast group G1. Clients C1 and C3 belonging to the multicast group G1 transmit control packets 100_1—100_3 (hereinafter collectively referred to as “100”) to join the multicast group G1 upstream of the relay devices R5, R6. , And R4

FIG. 6 shows a configuration example of the control packet 100. As shown in the figure, the control packet 100 includes a MAC address 110, a protocol header 120, and multicast control information 130. Among these, information of the participating group 131 or the leaving group 132 is set in the multicast control information 130.

Relay devices R5 and R6 that have received control packets 100_1 and 100_2 from clients C1 and C2 as shown in FIG. 5 respectively transmit control packets 100_4 and 100_5 to the adjacent upstream relay device R3. Also, the relay device R3 that has received the control packets 100_4 and 100_5 integrates the information as necessary, and transmits the control packet 100_6 to the further upstream relay device R2.

On the other hand, the relay device R4 that has received the control packet 100_3 from the client C3 similarly transmits the control packet 100_7 to the upstream relay device R2. Similarly, the relay device R2 transmits the control packet 100_8 to the upstream relay device R1.

[0012] Thereby, each of the relay apparatuses R1-R6 can know that the multicast information 200 of the multicast group G1 should be relayed. Therefore, the relay device R1 that has received the multicast information 200 from the Sano S1 has the direction opposite to the control packet 100_8 described above. That is, multicast information 200 is transmitted to relay apparatus R2.

[0013] Relay device R2 transmits multicast information 200 to relay devices R3 and R4, and relay device R3 transmits multicast information 200 to relay devices R5 and R6. Furthermore, the relay device

R5, R6, and R4 transmit multicast information 200 to clients C1 and C3, respectively.

[0014] In this way, the multicast information 200 is relayed in the opposite direction to the flow of the control packets 100_1—100_8, and each client C1 and C3 that has requested to join the multicast group G1 receives the multicast information 200, respectively. I can do it.

[0015] Conventionally, a procedure for exchanging information is not particularly provided between a sender, a receiver, and each receiver. That is, the sender sends information unilaterally, for example, at a constant cycle. In addition, the receiver only receives the multicast information by selecting the multicast group to receive the service and transmitting a control packet requesting the relay device to participate in the multicast group.

[0016] In addition, the relay device constituting the network that relays the multicast information has means for exchanging the participation / leaving group information between the adjacent relay devices as the routing information of the multicast. Relay in the shortest time.

[0017] For this reason, the transmission time of each transfer path varies in proportion to the increase in the number of relays of each relay device connecting the sender and each receiver, and the same multicast information is received between the receivers. Variation in time increases.

[0018] Multicast relay system for which delay should be taken into consideration

In the above general multicast relay system, it is assumed that each relay device R1-R6 relays the multicast information 200 in the shortest time. That is, when each of the relay devices R1 and R6 receives the multicast information 200, it relays the multicast information 200 to the downstream relay device without delay.

However, for example, in the distribution service of stock market information and other financial related information, if there is a variation in reception time for receivers belonging to the same multicast group, unfairness in transactions Will occur.

[0020] As a technique for avoiding the unfairness that causes a difference in the reception time of multicast information among receivers in this way, the impression and There is a video communication system that can communicate by exchanging opinions and the like via a network (for example, see Patent Document 1). O

[0021] In this video communication system, the time of the clock of each unit is unified according to the time information from the time distribution server, and then each multicast packet including video data and information indicating the distribution time is transmitted from the video distribution server. Delivered to the terminal device. Each terminal device receives the multicast packet, collects information on the delivery time and the reception time, for example, in a specific terminal device, calculates the maximum delivery delay time, and uses the maximum delivery delay time as a reference for each terminal device. The playback timing control unit adjusts the playback timing of the video data.

[0022] In addition, there is a multicast routing method in which an upper limit value of the delay time is set and a route is set so that a new participating node satisfies the delay time condition at the route setting stage (see, for example, Patent Document 2). .

[0023] Furthermore, there is also a multicast transfer route calculation method that sets a transfer route that reduces delay dispersion between users in a network composed of two layers, an access network and a core network (see, for example, Patent Document 3). ) ₀

[0024] On the other hand, as a delay time adjustment method of a mobile communication system, a plurality of radio base stations that communicate with mobile stations in the area using radio signals whose transmission timings are synchronized with each other and these radio base stations are integrated through a line transmission path. delay time adjustment method of a mobile communication system comprising a central station that is also known (e.g., see Patent Document 4.) ₀

[0025] Furthermore, the present invention relates to a synchronous operation system in which a data processing device and a plurality of relays are connected by a transmission line. As a method for synchronously operating the data processing device and the plurality of relays based on communication data, measures each delay time between each relay, thereby some corrects the reference time information (e.g., see Patent Document 5.) ₀

Patent Document 1: Japanese Patent Laid-Open No. 2003-235027

Patent Document 2: Japanese Patent Laid-Open No. 2001-244929

Patent Document 3: Japanese Patent Application Laid-Open No. 2004-27534

Patent Document 4: Japanese Patent Laid-Open No. 9-55979

Patent Document 5: Japanese Patent Laid-Open No. 11 355256 Disclosure of the invention

Problems to be solved by the invention

[0026] The above-mentioned Patent Documents 1 and 3 are related to multicast communication in consideration of delay. All of the forces remain the same in that each relay device relays in the shortest time.

That is, in Patent Document 1, the delay is absorbed by adjusting the video playback time on the receiver side according to the delivery delay time. In Patent Documents 2 and 3, the delay is set within a predetermined range or minimized at the stage of setting the multicast path.

[0028] As described above, in any of the above-mentioned Patent Documents 1 to 3, at the stage where the multicast information is actually relayed, no means is taken to eliminate the delay time difference between the receivers. Therefore, in Patent Document 1, the time at which each recipient actually receives information varies, and in Patent Documents 2 and 3, information is only transmitted according to the set route information. The delay time varies within the allowable delay range.

[0029] Also, Patent Document 4 is premised on wireless communication and is different from multicast communication. Thus, the radio signal transmission timing is adjusted so that all radio base stations match. In other words, there is a variation in the time when the signal transmitted from the central station through the transmission path reaches each radio base station.

[0030] Furthermore, in Patent Document 5, although the operation of each relay is synchronized, the time at which the transmitted data reaches each relay also varies.

Therefore, the present invention provides a multicast relay method and apparatus, and a multicast relay system, in which each receiver belonging to the same multicast group can receive the same multicast information at the same time or with a minimum time difference regardless of the delay time of the relay path. The purpose is to provide Another object of the present invention is to make it applicable to an existing multicast relay system without changing the application of a sender and a receiver.

Means for solving the problem

[0032] In order to solve the above-described problem, the multicast relay method according to the present invention provides a first malware. The first step of obtaining the transmission time of each multicast control information from each transmission source and the second delay time obtained by adding the transmission time to the first delay time included in the multicast control information are associated with each transmission source. The second step of storing the second delay time, the third step of including the maximum delay time in the second multicast control information and transmitting it upstream, and the multicast information to be relayed And a fourth step of transmitting to each transmission source by delaying the difference between the maximum delay time and each second delay time in order from the transmission source corresponding to the delay time.

[0033] That is, the first step force up to the third step is a processing step when relaying the multicast control information for notifying the participation or withdrawal of the multicast group toward the downstream force upstream, the fourth step Is a processing step when relaying multicast information from upstream to downstream.

[0034] In the first step, the transmission time of each source power of the first multicast control information (F1)

(tl) is obtained, and in the second step, a second delay time (d2 = dl +) obtained by adding a transmission time (tl) to the first delay time (dl) included in the first multicast control information (F1). tl) is stored in association with each transmission source.

[0035] In the third step, the maximum delay time (dmax) of the second delay time (d2) obtained in the second step is included in the second multicast control information (F2) and transmitted upstream. To do.

[0036] In the fourth step, transmission of multicast information to be relayed is started from the transmission source corresponding to the maximum delay time (dmax), and thereafter, the maximum delay time and each second delay time are determined. Are sequentially transmitted to each source with a difference of (dma _X -d2).

[0037] For example, if there are two transmission sources rl and r2, assuming that the transmission times obtained in the first step are tl_l and tl_2, respectively, and the first delay times are dl_l and dl_2, respectively, The second delay times d2_l = dl_l + tl_l and d2_2 = dl_2 + tl_2 are stored in association with the transmission sources rl and r2, respectively. Assuming that d2_l> d2_2, the maximum delay time (dmax) in the third step is the second delay time (d2_l) associated with the transmission source rl. Transmission of multicast information is started in order from the source rl, and multicast information is transmitted to the source r2 with a delay (dmax-d2_2 = d2_l-d2_2) delayed. [0038] Thereby, the reception timing of the other receivers can be delayed in accordance with the timing at which the terminal receiver receives the multicast information via the relay route that requires the maximum delay time, and the same multicast information can be transmitted. Regardless of the delay time of the relay route, it is possible to receive at almost the same time between each receiver.

[0039] The first delay time and the second delay time may each be associated with a multicast group.

[0040] That is, when there are a plurality of multicast groups, the first delay time and the second delay time are respectively associated with the multicast groups, so that the same multicast information is transferred to the relay path delay for each multicast group. It is possible to receive at approximately the same time between each receiver regardless of time.

[0041] Further, the first multicast control information includes transmission time information of the transmission source, and in the first step, the transmission time is based on the reception time of the first multicast control information and the transmission time information. Seek out.

[0042] Alternatively, in the first step, the transmission time may be obtained using a Ping or Hello packet.

[0043] Further, in order to solve the above-described problem, the multicast relay apparatus according to the present invention includes a time measuring unit for obtaining a transmission time of each transmission source power of the first multicast control information, and the multicast control information. Storage means for storing a second delay time obtained by adding the transmission time to the included first delay time in association with each transmission source; and a maximum delay time among the second delay times First transmission means included in the multicast control information and transmitted upstream, and multicast information to be relayed, in order from the transmission source corresponding to the maximum delay time, the maximum delay time and each second delay time And a second transmission means for transmitting to each of the transmission sources with a delay of each difference.

[0044] The first delay time and the second delay time may be associated with a multicast group, respectively.

[0045] Also, the first multicast control information includes transmission time information of the transmission source, and the time measurement means performs the transmission based on the reception time of the first multicast control information and the transmission time information. Ask for time. [0046] Alternatively, the time measuring means may obtain the transmission time using a Ping or Hello packet.

The invention's effect

According to the present invention, it is possible for each receiver belonging to the same multicast group to receive the same multicast information at the same time or with a minimum time difference regardless of the delay time of the relay route. This makes it possible to satisfy the requirements of applications that require fairness.

[0048] Further, since the present invention can be applied only to a relay device, it can be applied to an existing multicast relay system without changing the applications of a sender and a receiver.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the multicast forwarding method according to the present invention will be described with reference to FIGS. Fig. 1 shows a multicast communication system with the same configuration as in Fig. 5. Server S1 that is the sender of information of multicast group G1 and information from server S1 by requesting participation in multicast group G1 Are connected in a tree shape as shown in the figure via clients C1 and C3, and power relay devices R1-R6.

[0050] In FIG. 1, the symbol TO-T8 shown next to the transmission path connecting the server S1 and the relay apparatus Rl, the relay apparatuses R1 and R2, etc. is the transmission time (delay time) in each transmission path. It is assumed that

[0051] Width of control baguette

First, the clients C1 to C3 transmit control packets 100_1 to 100_3 to the relay devices R5, R6, and R4, respectively, as before. Relay devices R1-R6 are relay devices that implement the multicast relay method of the present invention. In this case, the generation of the tree that is the forwarding path is performed in the same way as in the conventional case shown in FIG. 5, in which the clients C1 to C3 each join the multicast group G1 to the adjacent upstream relay devices R5, R6, and R4. Is notified by transmitting control packets 100_1—100_3.

Relay devices R5 and R6 notify upstream relay device R3 of participation in multicast group G1 using control packets 10_1 and 10_2, respectively. At this time, the relay device R5 and R6 notifies delay time T6 (transmission time between relay device R3 and client C1) and delay time Τ7 (transmission time between relay device R3 and client C2) when relaying in multicast group Gl. In the figure, information on the multicast groups to participate in and the delay time are described, for example, under the control packets 10_1 and 10_2, respectively.

It is shown as Join (Gl, T6) and Join (Gl, T7).

In relay device R3, relay devices R5 and R6 and relay device R3 are based on the arrival times of control packets 10_1 and 10_2 for group participation from relay devices R5 and R6 and the time stamp 13ts included in control packets 10_1 and 10_2, respectively. T4 and T5 are calculated. The time stamp 13ts will be described later.

That is, it is understood that the relay device R3 force requires a transmission time of T6 + T4 to the client C1, and the relay device R3 force also requires a transmission time of T7 + T5 to the client C2. Therefore, in the relay device R3, for each output interface PoO and Pol, as shown later, the routing information is associated with the information of (*, G1, T6 + T4) and (*, G1, T7 + T5) as shown in the figure. Is stored in the route information storage unit 12.

[0055] Here, the code "*" indicates that when there are a plurality of servers that provide information on the multicast group G1, and when all servers that provide information on the multicast group G1 that is different from one specific server are specified. It is what you use. In the case of the figure, since only the server S1 is used, "S1" may be used instead of.

[0056] Next, the relay device R3 compares the transmission time of the output interface ΡοΟ side (Τ6 + Τ4) with the transmission time of the output interface Pol side (Τ7 + Τ5). Value

Max (T6 + T4, T7 + T5) is included in the control packet 10_3 and notified to the relay device R2. Therefore, the information included in the control packet 10_3 is Join (Gl, Max (T6 + T4, T7 + T5) as shown below the control packet 10_3 in FIG.

On the other hand, the relay device R4 that has received the control packet 100_3 from the client C3 transmits the control packet 10_4 including the information of Join (G1, T8) to the relay device R2, as in the relay devices R5 and R6.

[0058] Medium ϋ In device R2, for each of the output interfaces ΡοΟ and Pol,

(*, Gl, Max (T6 + T4, T7 + T5) + T2) and (*, G1, T8 + T3) are stored in the path information storage unit 12 in association with each other. Furthermore, the relay device R2 has Join (Gl, Max (Max (T6 + T4, T7 + T5) + T2, T8 + T3) The control packet 10_5 including the information is transmitted to the upstream relay device R1.

In the relay device R1, in the same manner, (Sl, Gl, Max (Max (T6 + T4, T7 + T5) + T2, T8 + T3) + Tl) is associated with the output interface PoO and the path information storage unit Store in 12.

[0060] By transmitting the control packets 10_1-10_5 (which may be collectively referred to as reference numeral 10) as described above from the downstream relay devices R4-R6 to the upstream relay devices R1-R3, In the relay devices R1 to R6, the maximum value of the downstream delay time is stored in the path information storage unit 12 in association with the respective output interfaces PoO and Pol.

[0061] Configuration example of control packet

FIG. 2 shows an example of the structure of the control packet 10. As shown in the figure, the control packet 10 is similar to the control packet 100 shown in FIG. 6, and the MAC address 11, the protocol header 12, and the multicast control. It consists of information 13. However, the multicast control information 13 includes a participating group group 13_1 and a leaving group group 13_2 as information on multicast groups to be joined and withdrawn (hereinafter simply referred to as groups).

[0062] In the example in the figure, the participating group group 13_1 includes information on the groups Gl, G2, and GX, and the leaving group group 13_2 includes information on G10, G12, and GY. In addition, each group Gl, G2 and GX of the participating group group 13_1 has a corresponding delay time.

[0063] In this way, in the control packet 10 in the figure, the information on participation and departure regarding a plurality of multicast groups is integrated, but this is a more complicated multicast system than the example shown in FIG. It is a control packet that can also be applied. For control buckets 10_1—10_5 in the figure, the only multicast group that participates is G1,

Information such as Join (Gl, T7) and Join (Gl, T6) corresponds to the information of participating group 13_1 in Fig. 2.

[0064] In addition, a time stamp 13ts may be inserted into the control packet 10 as information on the transmission time of the control packet. In this case, the upstream relay apparatus that receives the control packet 10 receives the time stamp 13ts and the control packet. By comparing the time when 10 is received, it is possible to measure the transmission time from the adjacent downstream relay device to the own device. [0065] Note that the transmission time between each relay device should be measured independently of the control packet 10 by a conventionally known Ping or Hello packet, in addition to the case where the time stamp 13ts is used. Is also possible.

[0066] Example of relay operation of multicast information

The multicast relay operation when multicast information 200 is transmitted from Sano S1 at the stage when transmission of control packets 10_1-10_5 as described above is completed will be described below with reference to FIG.

[0067] First, as a premise of FIG. 3, in order to simplify the following explanation, the maximum delay times of the output interfaces PoO and Pol are respectively set to “PoO maximum delay time” in the relay devices R2 and R3 where the transmission path branches. And “Pol maximum delay time”, the relationship of PoO maximum delay time> Pol maximum delay time is established.

[0068] The relay device R1 that has received the multicast information 200 from the server S1 has no branch here, and therefore does not perform delay insertion, and transmits the multicast information 200 to the relay device R2 as it is.

[0069] Since relay device R2 satisfies PoO maximum delay time> Pol maximum delay time, multicast information 200 is transmitted without delay insertion to the output interface PoO. On the other hand, for the output interface Pol, the multicast information 200 is transmitted by delaying the transmission timing by (PoO maximum delay time-Pol maximum delay time) as delay insertion.

[0070] Similarly to the relay device R2, the relay device R3 transmits the multicast information 200 to the output interface PoO without delay insertion, and the output interface Pol as delay insertion (PoO maximum delay time − Multicast information 200 is transmitted with the transmission timing delayed by Pol maximum delay time).

Each relay device R5, R6, and R4 transmits the multicast information 200 to the client CI C3.

[0072] In relay devices R2 and R3 that perform branching in this way, the difference in maximum delay time is absorbed, so that it becomes possible for clients C1 and C3 to receive multicast information 200 at approximately the same time.

[0073] In the above description, the case where the number of branches is 2 as in the relay devices R2 and R3. As explained above, even if there are more than 3 branches, the multicast interface 200 can be transmitted from each output interface with the output interface power, which is the maximum delay time, sequentially delayed by the difference delay time!

[0074] {column

Fig. 4 shows an example of the internal configuration of a relay device that implements the above-described relay method. The illustrated relay device Rn has PiO-Pi2 as an input interface and PoO-Po2 as an output interface! /.

A multicast processing unit 1 and scheduling processing units SP0-SP2 are connected between the input interface PiO-Pi2 and the output interface PoO-Po2. A multicast control unit 2 is connected to the multicast processing unit 1. Furthermore, the multicast processing unit 1 has a relay processing unit 11 and a route information storage unit 12. Of these, the route information stored in the route information storage unit 12 stores the route information exchanged with the adjacent relay device by the control packet 10_1-10_5, and includes multicast group information and transmission time (delay time). ), Path information such as input interface and output interface.

The relay processing unit 11 duplicates multicast information as necessary, and performs multicast information relay processing based on the route information stored in the route information storage unit 12.

The multicast control unit 2 instructs to update the information in the route information storage unit 12 according to the contents of the control packet. As in the past, the forwarding route changes according to the client's participation status in the multicast group, so it is necessary to update the route information at any time. Let the relay device Rn send control packet 10.

[0078] A transmitter 3 surrounded by a dotted line in the figure is included in each scheduling processor SP0-SP2, and performs delay insertion for each multicast group and transmits multicast information from each output interface PoO-Po2. is there.

Brief Description of Drawings

FIG. 1 is a block diagram for explaining an operation at the time of transmission of a control packet in an embodiment of a multicast relay method according to the present invention. FIG. 2 is a block diagram showing a configuration example of a control packet used in an embodiment of a multicast relay method according to the present invention.

FIG. 3 is a block diagram for explaining multicast information relay operation in an embodiment of the multicast relay method according to the present invention.

[4] It is a block diagram showing an embodiment of a relay device according to the present invention.

FIG. 5 is a block diagram for explaining a general multicast relay operation.

[FIG. 6] —A block diagram showing a configuration example of a control packet used for general multicast relay.

Explanation of symbols

C1 C3 client

G1 multicast group

PiO — Pi2 human interface

PoO—Po2 output interface

R1-R6 relay device

S1 server

SP0—SP2 scheduling processor

T0-T8 transmission time (delay time)

R1-R6 relay device

10— 1—10—5, 100— 1—100—8 Control packet

200 Multicast information

1 Multicast processor

2 Multicast controller

3 Transmitter

11 Relay processing section

12 Route information storage

In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims

The scope of the claims

[1] A first step for obtaining a transmission time of each source power of the first multicast control information, and a second delay time obtained by adding the transmission time to the first delay time included in the multicast control information. A second step of storing in association with the sender;

A third step of transmitting the maximum delay time included in the second multicast control information to the upstream in the second delay time; and

The multicast information to be relayed is transmitted to each source by delaying the difference between the maximum delay time and each second delay time in order from the source corresponding to the maximum delay time. Steps,

A multicast relay method comprising:

[2] In claim 1,

A multicast relay method, wherein the first delay time and the second delay time are associated with a multicast group, respectively.

[3] In claim 1,

The first multicast control information includes transmission time information of the transmission source, and in the first step, the transmission time is obtained based on the reception time of the first multicast control information and the transmission time information. Multicast relay method.

[4] In claim 1,

A multicast relay method characterized in that, in the first step, the transmission time is obtained using a Ping or Hello packet.

[5] Time measuring means for obtaining the transmission time of each source power of the first multicast control information;

Storage means for storing a second delay time obtained by adding the transmission time to the first delay time included in the multicast control information in association with each transmission source;

A first transmission means for including the maximum delay time in the second multicast control information and transmitting the second delay time to the upstream;

Multicast information to be relayed is sent to each source by delaying the difference between the maximum delay time and each second delay time in order from the source corresponding to the maximum delay time. A second transmission means to communicate;

A multicast relay device comprising:

[6] In claim 5,

A multicast relay device, wherein the first delay time and the second delay time are associated with a multicast group, respectively.

[7] In claim 5,

The first multicast control information includes transmission time information of the transmission source, and the time measuring means obtains the transmission time based on the reception time of the first multicast control information and the transmission time information. Multicast relay device to perform.

[8] In claim 5,

A multicast relay device characterized in that the time measuring means obtains the transmission time using a Ping or Hello packet.