CN1458771A - Multicasting messag transmission method base on two layer exchange device - Google Patents

Abstract

Translated fromChinese

本发明公开了一种基于二层交换设备的组播报文转发方法，该方法首先由二层交换设备从接入端口接收因特网组管理协议(IGMP)报文，判断报文中是否有虚拟局域网(VLAN)头，如果没有，给该报文加上接入端口的虚拟局域网标识(VLANID)构成虚拟局域网头，然后生成接入端口的VLANID和组播媒体接入控制(MAC)地址到收到该IGMP报文的物理端口的映射关系表，以及生成上行端口的虚拟局域网标识和组播媒体接入控制地址到收到该IGMP报文的物理端口的影射关系表，最后根据上述映射关系表进行组播报文的转发；采用上述方案可以解决二层交换设备上行端口收到的不带VLAN头的组播数据报文无法有效转发的问题，可以避免网络资源的浪费。

The invention discloses a method for forwarding multicast messages based on a layer-2 switching device. In the method, the layer-2 switching device first receives an Internet Group Management Protocol (IGMP) message from an access port, and judges whether there is a virtual local area network in the message (VLAN) header, if not, add the virtual LAN identifier (VLANID) of the access port to the message to form a virtual LAN header, and then generate the VLANID and multicast media access control (MAC) address of the access port to receive The mapping relationship table of the physical port of the IGMP message, and the mapping relationship table of the virtual local area network identification and the multicast media access control address of the generated uplink port to the physical port receiving the IGMP message, and finally perform according to the above mapping relationship table Forwarding of multicast packets; adopting the above scheme can solve the problem that the multicast data packets without VLAN headers received by the uplink port of the layer 2 switching device cannot be effectively forwarded, and can avoid the waste of network resources.

Description

Translated fromChinese

一种基于二层交换设备的组播报文转发方法A method for forwarding multicast packets based onLayer 2 switching equipment

技术领域technical field

本发明涉及通信网络中的报文转发方法，具体地说涉及基于二层交换设备的组播报文转发方法。The invention relates to a message forwarding method in a communication network, in particular to a multicast message forwarding method based on a two-layer switching device.

背景技术Background technique

目前在宽带网络中，用户终端通常会通过二层交换设备接入网络，其中最为常见的二层交换设备是支持802.1Q协议的以太网二层交换机(LANSWITCH)。下面以LANSWITCH为例说明组播报文的转发。所有由LANSWITCH接入网络的用户终端发出的报文都要被加上一个特殊的用于用户终端识别的标记，实际中，该标记通常为虚拟局域网(VLAN：Virtual Local Area Network)标签，此VLAN标签可以唯一标识此用户终端接入LANSWITCH的特定物理接口，即用户从接入端口发来的以太网格式的报文经过该交换机都将加上一个VLAN头以标识用户接入的端口位置。LANSWITCH对于收到的所有报文的转发方法如下：根据报文中的目的MAC地址和VLAN头中的VLANID查找二层转发表，即MAC地址和VLANID到物理端口的映射表，如果找到匹配项，则把报文从相应的物理端口转发出去；如果没有找到匹配项，则把报文向VLAN头中的VLANID对应的所有物理端口进行转发，相当于广播式发送。由于二层转发表是根据报文中的源MAC地址和VLANID以及收到此报文的物理端口来生成的，由于组播MAC地址不能当作标识终端设备的单播MAC地址使用，因此组播报文使用的是根本不会作为源媒体访问控制(MAC)地址出现的组播MAC地址作为报文的目的MAC地址，如果不做特殊处理的话，LANSWITCH无法为组播MAC地址生成二层转发表，LANSWITCH对于组播报文只能采取向所有端口以广播的方式发送，极大地浪费了系统带宽资源并严重影响LANSWITCH的性能。为了改善LANSWITCH对组播报文的处理，LANSWITCH截获用户的因特网组管理协议(IGMP)报文，以收到此IGMP报文的端口的VLAN标识(VLANID)和组播MAC地址生成关于此组播MAC地址的二层转发表，一旦LANSWITCH生成了关于组播MAC地址的二层转发表后，对于后面收到的组播数据报文，就完全可以按照普通报文一样查找二层转发表进行转发，从而避免LANSWITCH对组播报文的广播转发。Currently, in a broadband network, a user terminal usually accesses the network through aLayer 2 switching device, and the mostcommon Layer 2 switching device is an EthernetLayer 2 switch (LANSWITCH) supporting the 802.1Q protocol. The following uses LANSWITCH as an example to illustrate the forwarding of multicast packets. All packets sent by LANSWITCH user terminals connected to the network must be added with a special tag for user terminal identification. In practice, this tag is usually a virtual local area network (VLAN: Virtual Local Area Network) tag. This VLAN The label can uniquely identify the specific physical interface where the user terminal accesses LANSWITCH, that is, the Ethernet format message sent by the user from the access port will be added with a VLAN header to identify the port location of the user's access after passing through the switch. The forwarding method of LANSWITCH for all received messages is as follows: Search theLayer 2 forwarding table according to the destination MAC address in the message and the VLAN ID in the VLAN header, that is, the mapping table from the MAC address and VLAN ID to the physical port. If a match is found, Then the message is forwarded from the corresponding physical port; if no match is found, the message is forwarded to all physical ports corresponding to the VLANID in the VLAN header, which is equivalent to broadcast sending. Since theLayer 2 forwarding table is generated based on the source MAC address and VLAN ID in the packet and the physical port that received the packet, and since the multicast MAC address cannot be used as the unicast MAC address to identify the terminal device, the multicast The packet uses a multicast MAC address that does not appear as the source MAC address at all as the destination MAC address of the packet. If no special processing is performed, LANSWITCH cannot generate aLayer 2 forwarding table for the multicast MAC address. , LANSWITCH can only broadcast multicast packets to all ports, which greatly wastes system bandwidth resources and seriously affects the performance of LANSWITCH. In order to improve LANSWITCH's processing of multicast messages, LANSWITCH intercepts the user's Internet Group Management Protocol (IGMP) message, and uses the VLAN ID (VLANID) and multicast MAC address of the port that received the IGMP message to generate information about the multicast message. For theLayer 2 forwarding table of the MAC address, once LANSWITCH generates theLayer 2 forwarding table for the multicast MAC address, for the multicast data message received later, it can search theLayer 2 forwarding table for forwarding in the same way as ordinary messages , so as to prevent LANSWITCH from broadcasting and forwarding multicast packets.

由上述LANSWITCH对报文的处理中可以看出，当LANSWITCH收到一个不带VLAN头的报文时会自动的给此报文扩展一个VLAN头，而且这个VLAN头是以收到此报文的端口的VLANID来构造的。当LANSWITCH生成关于组播MAC地址的二层转发表时，其VLANID使用的是收到此IGMP报文的用户侧的接入端口的VLANID，而当LANSWITCH上行端口收到不带VLAN头的组播数据报文时(实际中，组播节目源都在网络侧，组播数据报文都是从LANSWITCH上行端口发过来的)，LANSWITCH会为这个报文加上上行端口的VLANID构成的VLAN头，而用户侧端口和上行侧端口的VLANID是不相同的，因此这将导致生成的关于组播MAC地址的二层转发表对于LANSWITCH上行端口收到的不带VLAN头的组播数据报文毫无作用，LANSWITCH仍会把组播报文当作广播报文处理，根据VLANID对应的物理端口进行转发，仍将浪费大量的网络资源。It can be seen from the processing of the message by LANSWITCH above that when LANSWITCH receives a message without a VLAN header, it will automatically extend a VLAN header to the message, and the VLAN header is based on receiving the message. The VLANID of the port is constructed. When LANSWITCH generates aLayer 2 forwarding table about the multicast MAC address, its VLAN ID uses the VLAN ID of the access port on the user side that received the IGMP message. For data packets (actually, the sources of multicast programs are all on the network side, and the multicast data packets are all sent from the uplink port of LANSWITCH), LANSWITCH will add a VLAN header composed of the VLANID of the uplink port to the packet, However, the VLAN IDs of the user-side port and the uplink-side port are different, so the generatedLayer 2 forwarding table about the multicast MAC address has no As a result, LANSWITCH will still treat multicast packets as broadcast packets, and forward them according to the physical port corresponding to the VLANID, which will still waste a lot of network resources.

发明内容Contents of the invention

本发明的目的在于提供一种避免网络资源浪费的基于二层交换设备的组播报文转发方法。The purpose of the present invention is to provide a layer-2 switching device-based multicast message forwarding method that avoids waste of network resources.

为达到上述目的，本发明提供的基于二层交换设备的组播报文转发方法，包括：In order to achieve the above object, the multicast message forwarding method based on the two-layer switching equipment provided by the present invention includes:

(1)二层交换设备从接入端口接收因特网组管理协议(IGMP)报文；(1)Layer 2 switching device receives Internet Group Management Protocol (IGMP) message from the access port;

(2)判断报文中是否有虚拟局域网(VLAN)头，如果有，转步骤(3)，否则给该报文加上接入端口的虚拟局域网标识(VLANID)构成虚拟局域网头；(2) judge whether there is a virtual local area network (VLAN) head in the message, if there is, go to step (3), otherwise add the virtual local area network identification (VLANID) of the access port to the message to form a virtual local area network head;

(3)生成接入端口的虚拟局域网标识(VLANID)和组播媒体接入控制(MAC)地址到收到该IGMP报文的物理端口的映射关系表，以及生成上行端口的虚拟局域网标识和组播媒体接入控制地址到收到该IGMP报文的物理端口的影射关系表；(3) generate the virtual local area network identification (VLANID) of the access port and the mapping relationship table of the multicast media access control (MAC) address to the physical port receiving the IGMP message, and generate the virtual local area network identification and group of the uplink port A mapping relationship table from the broadcast media access control address to the physical port receiving the IGMP message;

(4)根据上述映射关系表进行组播报文的转发。(4) Forwarding the multicast message according to the above mapping relationship table.

本发明在生成组播二层转发表时使用了LANSWITCH的上行端口的VLANID，增加了一个LANSWITCH的上行端口的VLANID和组播MAC地址到收到此IGMP报文的物理端口的映射关系表，由于在生成组播二层转发表时建立两个转发表：一个转发表中的VLANID使用收到IGMP加入报文的用户侧端口的VLANID，另一个转发表中的VLANID使用LANSWITCH的上行端口的VLANID，从而解决了LANSWITCH上行端口收到的不带VLAN头的组播数据报文无法有效转发的问题，因此采用本发明所述方法转发IGMP组播报文可以避免网络资源浪费。The present invention has used the VLANID of the uplink port of LANSWITCH when generating the multicast two-layer forwarding table, has increased the VLANID of the uplink port of LANSWITCH and the mapping relationship table of the multicast MAC address to the physical port that receives this IGMP message, because Create two forwarding tables when generating themulticast Layer 2 forwarding table: the VLANID in one forwarding table uses the VLANID of the user-side port that received the IGMP join message, and the VLANID in the other forwarding table uses the VLANID of the uplink port of LANSWITCH, Therefore, the problem that the multicast data message without the VLAN header received by the LANSWITCH uplink port cannot be effectively forwarded is solved, so the method of the present invention can avoid the waste of network resources by forwarding the IGMP multicast message.

附图说明Description of drawings

图1是本发明方法的实施例流程图。Fig. 1 is the flow chart of the embodiment of the method of the present invention.

具体实施方式Detailed ways

下面结合附图对本发明作进一步详细的描述。The present invention will be described in further detail below in conjunction with the accompanying drawings.

通常，经二层交换设备处理的组播报文有两种：IGMP报文和组播数据报文。这是不同的两种报文，虽然他们都使用组播MAC地址作为目的MAC地址：IGMP报文是用户终端通告网络设备需要某个组播服务的信令控制报文，用户只有在需要和离开某个组播服务时，才会发出相应的IGMP报文，而且IGMP报文的目的MAC地址和相应的组播数据报文的目的MAC地址采用完全相同的组播MAC地址；而组播数据报文才是真正的承载组播服务内容的数据报文。因此，二层交换设备生成组播报文二层转发表需要IGMP报文的参与才可能实现，然后利用二层转发表进行组播数据报文的转发。Generally, there are two types of multicast packets processed byLayer 2 switching devices: IGMP packets and multicast data packets. These are two different types of messages, although they both use the multicast MAC address as the destination MAC address: the IGMP message is a signaling control message for the user terminal to notify the network device that a certain multicast service is needed. When a certain multicast service is provided, the corresponding IGMP message will be sent out, and the destination MAC address of the IGMP message and the destination MAC address of the corresponding multicast data message use exactly the same multicast MAC address; while the multicast data message The text is the real data packet carrying the content of the multicast service. Therefore, the generation of theLayer 2 forwarding table of the multicast message by theLayer 2 switching device requires the participation of the IGMP message, and then theLayer 2 forwarding table is used to forward the multicast data message.

为了使二层交换设备能够实现带VLAN头和不带VLAN头的组播报文的非广播式转发，本发明在生成组播二层转发表时多建立一个二层转发表，这样通过两个二层转发表即可实现带VLAN头和不带VLAN头的组播报文的非广播式转发。下面通过以太网二层交换机(LANSWITCH)为例说明本发明。In order to enable the two-layer switching equipment to realize the non-broadcast forwarding of multicast messages with VLAN headers and without VLAN headers, the present invention sets up a second-layer forwarding table when generating the multicast two-layer forwarding table, so that through two TheLayer 2 forwarding table can implement non-broadcast forwarding of multicast packets with and without VLAN headers. The present invention will be described below by taking anEthernet Layer 2 switch (LANSWITCH) as an example.

图1是本发明方法的实施例流程图。按照图1，实现本发明共有5个步骤。首先，LANSWITCH在步骤1，从接入端口接收因特网组管理协议(IGMP)报文，然后在步骤2判断该报文中是否有虚拟局域网(VLAN)头，如果有，转步骤4，否则在步骤3给该报文加上接入端口的虚拟局域网标识(VLANID)构成虚拟局域网头，例如，对于不支持802.1Q协议的用户终端发出的IGMP报文都不会有VLAN头，因此IGMP报文的VLAN头都是由LANSWITCH自动加上的，且是以接入端口的虚拟局域网标识(VLANID)构成的；然后转步骤4；在步骤4，生成接入端口的虚拟局域网标识(VLANID)和组播媒体接入控制(MAC)地址(即IGMP报文的目的MAC地址)到收到该IGMP报文的物理端口的映射关系表，生成该表是传统的LANSWITCH的功能，这样做是为了和传统兼容，因为如果LANSWITCH上连的上层设备支持802.1Q协议时，它可以发出带有接入端口的VLANID的组播数据报文；同时生成上行端口的虚拟局域网标识和组播媒体接入控制地址(即IGMP报文的目的MAC地址)到收到该IGMP报文的物理端口的映射关系表；最后在步骤5，根据上述映射关系表进行组播数据报文的转发。Fig. 1 is the flow chart of the embodiment of the method of the present invention. According to Fig. 1, realize the present invention has 5 steps altogether. First, LANSWITCH receives the Internet Group Management Protocol (IGMP) message from the access port instep 1, then judges instep 2 whether there is a virtual local area network (VLAN) header in the message, if so, turn tostep 4, otherwise instep 2 3 Add the virtual local area network identifier (VLANID) of the access port to the message to form a virtual local area network header, for example, the IGMP message sent by a user terminal that does not support the 802.1Q protocol will not have a VLAN header, so the IGMP message The VLAN header is automatically added by LANSWITCH, and is composed of the virtual local area network identification (VLANID) of the access port; then turn tostep 4; instep 4, generate the virtual local area network identification (VLANID) and multicast of the access port The mapping relationship table from the media access control (MAC) address (that is, the destination MAC address of the IGMP message) to the physical port that receives the IGMP message. This table is generated by the function of traditional LANSWITCH. This is done for compatibility with traditional , because if the upper layer equipment connected on LANSWITCH supports the 802.1Q protocol, it can send out a multicast data packet with the VLANID of the access port; simultaneously generate the virtual local area network identification and the multicast media access control address of the uplink port (ie The destination MAC address of IGMP message) to the mapping relationship table of the physical port that receives this IGMP message; Finally instep 5, carry out the forwarding of multicast data message according to above-mentioned mapping relationship table.

当LANSWITCH上行端口收到不带VLAN头的组播数据报文时，LANSWITCH会自动为这个报文加上上行端口的VLANID构成的VLAN头，然后LANSWITCH根据报文中的组播MAC地址，即组播数据报文的目的MAC地址和上行端口的VLANID查找二层转发表，由于步骤3已经生成了上行端口的VLANID和相应的组播MAC地址到收到该IGMP报文的物理端口的映射关系表，LANSWITCH把组播数据报文直接转发到这个物理端口，保证了发出IGMP报文的用户能够收到组播数据报文，获得组播服务。When the LANSWITCH uplink port receives a multicast data packet without a VLAN header, LANSWITCH will automatically add a VLAN header composed of the VLANID of the uplink port to the packet, and then LANSWITCH will use the multicast MAC address in the packet, that is, the group The destination MAC address of the broadcast data message and the VLANID of the uplink port are searched for theLayer 2 forwarding table, becausestep 3 has generated the mapping relationship table of the VLANID of the uplink port and the corresponding multicast MAC address to the physical port receiving the IGMP message , LANSWITCH directly forwards the multicast data message to this physical port, which ensures that the user who sends the IGMP message can receive the multicast data message and obtain the multicast service.

Claims (2)

1, a kind of method for forwarding multicast message based on two-layer switching equipment comprises:

(1) two-layer switching equipment is from access interface receiving internet igmpinternet (IGMP) message;

(2) judge whether the Virtual Local Area Network head is arranged in the message,, change step (3), otherwise the VLAN ID (VLANID) of adding access interface for this message constitutes the VLAN head if having;

(3) generate the VLAN ID (VLANID) of access interface and multicast medium access control (MAC) address mapping relations table, and the VLAN ID of generation uplink port and multicast Media Access Control Address are to the mapping relations table of the physical port of receiving this IGMP message to the physical port of receiving this IGMP message;

(4) carry out the forwarding of multicast message according to above-mentioned mapping relations table.

2, method for forwarding multicast message according to claim 1 is characterized in that: described two-layer switching equipment is a layer 2 ethernet switch.

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