GMRP protocol Parsing

Gmrp (garp multicast registry protocol, garp multicast registration protocol) is a multicast registration protocol Based on garp, used to maintain multicast registration information in the switch. All vswitches that support gmrp can receive multicast registration information from other vswitches and dynamically update the local multicast registration information, at the same time, it can also spread the local multicast registration information to other switches. This information exchange mechanism ensures the consistency of multicast information maintained by all devices that support gmrp in the same exchange network. When a host wants to join a multicast group, it sends a gmrp message. The switch adds the port from which gmrp is received to the multicast group, and broadcasts the gmrp to the message in the vlan where the receiving port is located, the Multicast Source in a vlan can know the existence of multicast members. When a Multicast Source sends multicast packets to a multicast group, the vswitch only forwards the multicast packets to the ports connected to the multicast group members, thus implementing layer-2 multicast in the vlan. The switch periodically sends GMRP queries. If the host wants to stay in the multicast group, it will respond to GMRP queries. In this case, the switch does not perform any operations; if the host does not want to stay in the multicast group, it can send a leave message or not respond to periodic GMRP queries. Once the switch receives the host leave information or does not receive the response information during the time specified by the timer (leave all timer), it deletes the host from the multicast group. IEEE 802.1p is the traffic priority control standard, which works on the sub-layer of Media Access Control (MAC. It enables L2 switches to provide traffic priority and Dynamic Multicast filtering services. The IEEE 802.1p standard also provides the multicast traffic filtering function to ensure that the traffic does not exceed the second-layer switching network range. The IEEE 802.1p header includes a three-bit priority field, which supports grouping data packets into various traffic types. IEEE strongly recommends network administrators to implement these traffic types, but it does not require mandatory use. The traffic type can also be defined as the second-level service quality (QoS) or service class (CoS) and implemented on network adapters and switches without any reserved settings. IEEE 802.1p traffic is simply classified and sent to the destination without the Bandwidth Reservation Mechanism. IEEE 802.1p is an extended protocol of IEEE 802.1q (VLAN label Protocol), which works collaboratively. The IEEE 802.1q standard defines the labels added for Ethernet MAC frames. VLAN tags have two parts: vlan id (12 bits) and priority (3 bits ). The IEEE 802.1q VLAN standard does not define or use a priority field, which is defined in IEEE 802.1p. Eight priorities are defined in IEEE 802.1p. The highest priority is 7, which is applied to key network traffic, such as route selection Information Protocol (RIP) and Open Shortest Path priority (OSPF) protocol route table update; priority 6 and 5 are mainly used for delay-sensitive applications, such as interactive videos and voice; Priority 4 to 1 is mainly used for controlled-load applications, for example, streaming multimedia and business-critical traffic; Priority 0 is the default value and is automatically enabled without other priority values. The IEEE 802.1p Protocol also defines the GARP (general Attribute Registration Protocol ). The Attribute here refers to attributes such as the multicast MAC address, port filtering mode, and VLAN. The GARP Protocol can actually define the characteristics that many switches should have, such as GMRP (GARP Multicast registry Protocol, Multicast Registration Protocol) and GVRP (garp vlan registry Protocol, virtual LAN Registration Protocol) the two protocols will define other features based on the needs of network development in the future. GARP defines how Ethernet switches exchange such characteristic information, how to send data packets, how to handle received data packets, and so on. GMRP is a dynamic layer-2 multicast registration protocol, which is similar to IGMP (Interent multicast protocol) in many aspects. For IP addresses, Class d ip addresses are multicast addresses. In fact, each IP multicast address corresponds to a multicast MAC address, IEEE 802.1p is used to register and remove multicast members on an Ethernet switch based on the multicast MAC address. IGMP is managed based on the multicast IP address. Of course, if the Ethernet switch does not implement the GMRP protocol, you can only achieve multicast through static configuration. So why do I need a layer-2 multicast protocol? Like the IGMP protocol, if we set up a multicast group in our own LAN, our lan may contain many switches. If these switches do not implement the layer-2 multicast protocol, when a group member sends a packet to another group member, the switch broadcasts the packet to all ports. Because the vswitch does not know which port has been added to the multicast group, the only solution is to configure the vswitch as the administrator. Only in this way can the transmission of such broadcast forwarding packets be restricted. However, multicast itself is dynamic, so it is unrealistic to implement multicast through administrator configuration. Therefore, a layer-2 multicast protocol is required to dynamically manage team members. This is why layer-2 multicast protocol is required. At present, many high-end switches implement IEEE 802.1p and IEEE 802.1q protocols (This section will be detailed later) as a major performance indicator. GVRP is a VLAN protocol, because it and GMRP are based on GARP, so they are closely related, they all need to operate on the database of the switch, the specific definitions of this Protocol are described in the IEEE 802.1q Protocol below. Author mx11