KR20040055289A - Method for selecting rendezvous point in multi-casting communication - Google Patents

Abstract

PURPOSE: A method for selecting an RP(Rendezvous Point) in multicasting communication is provided to select an RP by using an existing routing protocol. CONSTITUTION: When an MR(Multicast Router) receives a routing protocol message(S301), it checks whether the message is valid(S302). If the message is valid, the MR checks whether a domain identifier and a group address are valid(S303,S304). If the domain identifier and the group address are valid, the MR compares an RP select priority value included in the received message and its own RP select priority value(S305). If the RP select priority value of the MR is higher than the RP select priority value included in the message, the MR discriminates whether transmission valid time has elapsed(S307). If the transmission valid time has not elapsed, the MR transmits a message that the MR is an RP of a corresponding multicast group to a different MR(S309) and is standby(S310).

Description

Rendezvous point selection method in multicasting communication {Method for selecting rendezvous point in multi-casting communication}

The present invention relates to a Rendezvous point (RP) selection method for multicasting communication, and more particularly, to a method for selecting an RP through a routing protocol for multicasting using the Internet.

Although broadcasting and multimedia services using the Internet are multilateral communication services for multiple receivers, most internet broadcasting and multimedia transmission systems use a unicast scheme. This increases the bandwidth usage in the network and limits the number of users who can access the network, which is a major cause of lowering the efficiency of communication equipment. In addition, redundant transmission of unicast traffic can cause network overload and bottlenecks, resulting in overall degradation of service quality.

In contrast, the multicast method is a method suitable for a multi-party group communication service such as Internet broadcasting, and can efficiently use network resources and a communication system.

1 is a block diagram of a multicasting network.

The multicast domain 10 consists of a multicast server 101, a plurality of multicast routers (MRs) 102, and a multicast client 103.

The MR 102 performs a function of constructing a multicast tree using a multicast routing protocol, constructing a multicast forwarding table using the constructed tree, and multicast traffic corresponding to the multicast using the constructed multicast forwarding table. It is the core of a multicast network that also performs the function of delivering to a router or multicasting client 103. In this case, the MR 102 uses Protocol Independent Multicast (PIM) as an intra domain multicast routing protocol.

The multicast server 101 performs a function of generating corresponding multicasting traffic according to the multicast service. To perform this function, data or content such as audio information or video information is changed to Internet data.

The multicast client 103 receives a corresponding multicasting traffic according to a multicast service and decodes the information into information suitable for a general user. Multicast client 103 may also request MR 102 to join and leave the group using an Internet Group Management Protocol (IGMP) message.

Multicasting consists of a procedure of receiving a data by joining a desired multicast group by viewing information provided by each subscriber, such as multicast address setting, session creation and notification, etc. by a service provider.

The service provider first sets a multicast address for each content transport stream for data or content transmission. Multicast addresses should be set up so that they do not overlap with multicast addresses used in other groups or sessions. Next, the service provider creates a session and announces to the customer information about the various content and sessions along with the multicast address.

The receiving host (customer) joining the multicast session informs MR 102 that he or she is a member of the desired multicast group using IGMP. Based on this, the MR receives the multicast data corresponding to the group. Send data or content to a multicast group subscriber. In this case, as a routing technology for data transmission to a multicast subscriber, a multicast routing protocol and a technology of binding to a multicast network for a receiving host may be used. A multicast routing protocol called PIM is mainly used.

The multicast routing protocol is a kind of signaling protocol constituting a transmission path or a multicast tree between a transmitter and a receiver. By the routing protocol, each router sets up a multicast forwarding table for the corresponding group and uses it for multicast data transmission.

The present invention relates to a method for selecting an RP from among MRs performing multicasting by constructing a multicast routing tree in performing such multicasting. The RP uses the configured routing tree to deliver multicast traffic to the receiver.

Conventional RP selection methods include a method in which a router administrator directly selects an RP, a Bootstrap router (BSR) selects an RP, or a separate routing protocol for selecting an RP.

If the administrator directly selects the RP, the ability to replace the backup RP in case of an abnormality of the selected RP decreases. When using a separate routing protocol, the cost of designing a separate protocol required for the router and Since the designation of the priority value, which is the criterion for selecting RP, is collectively and arbitrarily without any other criteria, there is a disadvantage in selecting an RP that can optimize data transmission.

Therefore, the present invention was devised to solve the above disadvantages, and the object and technical problem to be achieved by the present invention can be selected by using an existing routing protocol without using a separate protocol for RP selection. The present invention provides a method for selecting a rendezvous point for multicasting communication.

Another object and technical problem to be achieved by the present invention is to select a rendezvous point for multicasting communication to select the RP to optimize the data transmission by setting the priority value of the RP selection criteria based on a predetermined criterion In providing a method.

1 is a block diagram of a multicasting network.

2 is a message format of a routing protocol newly defined in the present invention for selecting a rendezvous point.

3 is a flowchart for processing a newly defined multicast routing protocol message to select a rendezvous point.

<Description of the symbols for the main parts of the drawings>

S301: Multicasting Router Receives Routing Protocol Message

S302: valid message checking step

S303: Validation step of domain identifier

S304: Step of validating group address

S305: comparing RP_m and RP_MR

S307: Step of determining whether the transmission valid time has elapsed

In order to achieve the above object and technical problem, the rendezvous point selection method for multicasting communication provided by the present invention newly defines a multicasting routing protocol message and processes the message in a predetermined manner to select an RP. And processing the message comprises: receiving, by the multicasting router (MR), a newly defined routing protocol message; Determining whether the message is valid; Determining a domain identifier of the message; Determining a group address of the message; And comparing the RP selection priority value of the MR with the RP selection priority value included in the message.

Preferably, if the priority value of the MR is higher than the priority value included in the message, characterized in that it further comprises the step of determining whether the elapsed valid time of the message has elapsed.

Preferably, the priority value is characterized in that the highest priority value is set to an MR having the largest interface bandwidth with another MR among the plurality of MPs.

Preferably, the priority value is characterized in that the highest priority value is set to an MR having the largest buffer size compared to the other MRs among the plurality of MPs.

Preferably, the newly defined multicasting routing protocol message uses a PIM message format and is defined by newly designating a value of a message type region included in the PIM message format.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, the configuration, operation, and optimal embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which like reference numerals are used to designate like elements. It is noted that in the description of the drawings, components of other drawings may be cited if necessary.

2 is a message format of a routing protocol newly defined in the present invention for selecting an RP.

This message format uses the format of the PIM routing protocol.

Version 201 is a part that specifies the version of the message as it is, is 4 bits in size. PIM currently uses version 2.

Type 202 specifies a message type with a size of 4 bits. Currently, PIM uses 9 types by setting message types from 0 to 8. In order to achieve the object of the present invention, it is mentioned that a new routing protocol message is defined, and a new type of message is defined and used by setting the Type 202 to 10.

Reserved 203 is a reserved portion of 8 bits and is set to 0 and is an unprocessed area when received.

Checksum 204 is 16 bits in size and uses standard Internet checksum rules. After adding the contents of the message bit by bit, 16-bit complement is taken. When checking the checksum of the received message, if it gets 0 as a result, it is determined that there is no error.

Prefix Count 205 is an 8-bit size that indicates the number of multicast group addresses included in the message. The 8-bit size allows up to 256 group addresses.

Priority 206 is an 8-bit size that specifies the priority value of the RP, with 0 being the highest priority value. This value plays an important role as a criterion in selecting the RP and shows a method of setting the priority value in FIG. 4.

Holdtime 207 is a 16-bit size specifying the validity of the transmission process of this message. Messages that have expired will be discarded without being processed.

The Unicast RP Address 208 is a 32-bit block that specifies the MR's interface IP address, which can be selected as an RP.

Domain ID 209 is a 32-bit size that specifies the identifier of the multicast domain to use this to identify the domain performing the multicast service.

Group Address = 1 to Group Address = n (210) specifies a multicast address used in the corresponding domain. Multiple addresses can be used depending on the multicast service.

3 is a flowchart of processing a newly defined multicast routing protocol message to select an RP.

When the MR 102 receives the routing protocol message (S301), it checks whether the message is valid by checking the version, format, and checksum of the message (S302). If an invalid value is found, the received message is discarded.

If the received message is a valid message, it is checked whether the domain identifier and the group address are valid (S303, S304). If the domain identifier or group address is invalid in the multicast domain that performs the multicast service, it is discarded without further processing.

When the domain identifier or the group address is valid, the RP selection priority value RP_m included in the received message is compared with the MR own RP selection priority value RP_MR included in the received message (S305). If RP_MR ?? RP_m, the MR is subordinate to priority, the MR does not transmit a message (RP message) indicating that he is the RP of the multicast group to another MR or the multicast client 103 (S306). If RP_MR ?? RP_m, MR is selected as RP and RP message can be transmitted to other MR.

However, RP_MR ?? RP_m can cause problems because RP messages are sent in an infinite time range, which means that the MR continuously receives another multicasting router message in real time and changes the RP according to the contents of the other router messages. Because it can. If an RP message is sent in an indefinite time range, this may solve the previous problem that the RP could be fixed.

Therefore, in transmitting an RP message to another MR, a condition is required to transmit the RP message within a finite time (transmission valid time) from when the multicasting router message is received. The MR 102 has a built-in timer (not shown) to determine whether the RP message transmission valid time has elapsed.

Therefore, in the present invention, when the RP selection priority value of the MR is higher than the RP selection priority value included in the message (RP_MR ?? RP_m), determining whether the valid time of transmission to another MR of the RP message has elapsed (S307). It further includes.

If the transmission valid time has not elapsed, it transmits a message (RP message) indicating that it is the RP of the multicast group to another MR (S309) and waits for reception of another message (S310). If so, the MR registers itself as an RP (S308).

In summary, the multicast router 102 performs a function of managing a list of candidate RPs and multicast group addresses. In addition, when the RP selection priority value is high, the multicast router 102 indicates that the multicast router 102 is the RP of the corresponding multicast group. Messages are sent periodically to other multicast routers in the multicast domain.

Table 1 shows an example in which a priority value for selecting a rendezvous point is set.

In a multicast environment, the RP constructs a multicasting tree to establish a valid multicasting path, and transmits and receives multicast traffic to the corresponding node. It also manages the multicast group address list according to the multicasting service. Therefore, the RP should be set as a multicast router with higher bandwidth of the interface than the other multicast routers and a good MR resource (larger buffer size). Therefore, priorities should be set considering these factors. Table 1 is an example of setting priority values. The types of multicast interfaces are classified as follows in consideration of bandwidth and buffer size.

An interface having a bandwidth of 10GMbps (BW) is classified as A, an interface having a BW between 10GMbps and 1GMbps, B, an interface having a BW between 1GMbps and 100Mbps, and an interface having a BW of less than 100Mbps as D. In case of A, the priority is set to 11, 12, 13 according to the buffer size (BS). In case of B, the priority is set to 21, 22, 23 according to the buffer size. In the case of D, 31, 32, 33, the priority is set to 41, 42, 43 according to the buffer size.

Although the preferred mode of operation of the present invention has been described in detail by way of example, those skilled in the art will appreciate that the present invention may be made without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that the present invention may be implemented in various ways. Accordingly, modifications to the foregoing embodiments of the present invention will not depart from the techniques of the present invention.

The present invention can select the RP using the existing routing protocol without using a separate protocol for selecting the RP can reduce the cost of the separate protocol required for the multicast router.

The present invention can also optimize data transmission by setting a priority value, which is a criterion for selecting RP, based on the capability of the system resources of the MR, thereby improving the reliability of the multicast environment.

Claims (5)

A multicast router receiving a newly defined multicasting routing protocol message from the multicasting server on a multicast domain composed of a multicast server, a plurality of multicast routers (MRs), and a multicast client analyzes the message. Rendezvous point (RP) is selected from a number of MRs and the analysis of the message is: Determining whether the message is valid; Determining whether a domain identifier of the message is valid; Determining whether the group address of the message is valid; And In the multicasting communication, the multicast router receiving the message compares its RP selection priority value (RP_MR) with the RP selection priority value (RP_m) included in the message. How to select rendezvous points. The method of claim 1, And if the RP_MR is larger than the RP_m, determining whether one multicast router receiving the message has passed a transmission valid time for transmitting a message indicating that the message is an RP to another MR. How to select rendezvous points in casting communication. The method of claim 1 or 2, wherein the priority value is The method of selecting a rendezvous point in multicasting communication, characterized in that the highest priority value is set to an MR having the largest interface bandwidth with another MR among the plurality of MPs. The method of claim 1 or 2, wherein the priority value is The method of selecting a rendezvous point in multicasting communication, characterized in that the highest priority value is set to an MR having the largest buffer size compared to the other MRs among the plurality of MPs. The method of claim 1, wherein the newly defined multicasting routing protocol message is The method of selecting a rendezvous point in a multicasting communication using a message format of a PIM method and defining a new value of a message type region included in the message format of the PIM method.