「IGMP」- 报文格式

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IGMPv1

Version：IGMP 版本，IGMPv1 值为 1；

Type：报文类型。该字段有以下两种取值：
1）0x1：表示普遍组查询报文（Memebership Query ）；
2）0x2：表示成员关系报告报文（Memebership Report）；

Group Address：组播组地址。
1）在 Memebership Query 中，该字段设为 0；
2）在 Memebership Report 中，该字段为成员加入的组播组地址；

在 IP Layer 中，Memebership Query 与 Memebership Report 均为组播报文，目的地址为 224.0.0.1（所有的设备都要进行响应）。

Memebership Query

Frame 760: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_49:02:cb (00:e0:fc:49:02:cb), Dst: IPv4mcast_01 (01:00:5e:00:00:01)
Internet Protocol Version 4, Src: 192.168.2.254, Dst: 224.0.0.1
Internet Group Management Protocol
    [IGMP Version: 1]
    Type: Membership Query (0x11)
    Reserved: 00
    Checksum: 0xeeff [correct]
    [Checksum Status: Good]
    Multicast Address: 0.0.0.0

Memebership Report

Frame 771: 46 bytes on wire (368 bits), 46 bytes captured (368 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_5a:28:cc (54:89:98:5a:28:cc), Dst: IPv4mcast_02:02:02 (01:00:5e:02:02:02)
Internet Protocol Version 4, Src: 192.168.2.1, Dst: 239.2.2.2
Internet Group Management Protocol
    [IGMP Version: 1]
    Type: Membership Report (0x12)
    Reserved: 00
    Checksum: 0xfcfa [correct]
    [Checksum Status: Good]
    Multicast Address: 239.2.2.2

IGMPv2

Type，报文类型。该字段有以下四种取值：
1）0x11：表示 Membership Query 报文。
—- IGMPv2 的 Membership Query 报文分为 General Query 和 Group-Specific Query 两类，
—- 具体是哪类，取决于 Group Address 是否有值。
2）0x12：表示 IGMPv1 Membership Report 报文；
3）0x16：表示 IGMPv2 Membership Report 报文；
4）0x17：表示 Leave Group 报文。

Max Response Time，表示主机响应查询返回报告的最大时间：
1）对于 General Query 报文，最大响应时间默认为 10 秒；
2）对于 Group-Specific Query 报文（当 Last Report 离组时发送），最大响应时间默认为 1 秒；

Group Address，组地址：
1）在 Membership Query 中，设置为 0.0.0.0；
2）在 Group-Specific Query 中，为需要查询的组地址；
3）在 Membership Report 或 Leave Group 中，组地址为需要报告或离开的组地址。

Packet Example: General Query (Membership Query)

Frame 956: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_49:02:cb (00:e0:fc:49:02:cb), Dst: IPv4mcast_01 (01:00:5e:00:00:01)
Internet Protocol Version 4, Src: 192.168.2.254, Dst: 224.0.0.1
Internet Group Management Protocol
    [IGMP Version: 2]
    Type: Membership Query (0x11)
    Max Resp Time: 10.0 sec (0x64)
    Checksum: 0xee9b [correct]
    [Checksum Status: Good]
    Multicast Address: 0.0.0.0

Packet Example: Group-Specific Query (Membership Query)

Frame 1001: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_49:02:cb (00:e0:fc:49:02:cb), Dst: IPv4mcast_02:02:02 (01:00:5e:02:02:02)
Internet Protocol Version 4, Src: 192.168.2.254, Dst: 239.2.2.2
Internet Group Management Protocol
    [IGMP Version: 2]
    Type: Membership Query (0x11)
    Max Resp Time: 1.0 sec (0x0a)
    Checksum: 0xfdf0 [correct]
    [Checksum Status: Good]
    Multicast Address: 239.2.2.2

Packet Example: IGMPv2 Membership Report

与 IGMPv1 Membership Report 格式类似： 

Frame 869: 46 bytes on wire (368 bits), 46 bytes captured (368 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_5a:28:cc (54:89:98:5a:28:cc), Dst: IPv4mcast_02:02:02 (01:00:5e:02:02:02)
Internet Protocol Version 4, Src: 192.168.2.1, Dst: 239.2.2.2
Internet Group Management Protocol
    [IGMP Version: 2]
    Type: Membership Report (0x16)
    Max Resp Time: 0.0 sec (0x00)
    Checksum: 0xf8fa [correct]
    [Checksum Status: Good]
    Multicast Address: 239.2.2.2

Packet Example: Leave Group

Frame 1000: 46 bytes on wire (368 bits), 46 bytes captured (368 bits) on interface -, id 0
Ethernet II, Src: HuaweiTe_5a:28:cc (54:89:98:5a:28:cc), Dst: IPv4mcast_02:02:02 (01:00:5e:02:02:02)
Internet Protocol Version 4, Src: 192.168.2.1, Dst: 239.2.2.2
Internet Group Management Protocol
    [IGMP Version: 2]
    Type: Leave Group (0x17)
    Max Resp Time: 0.0 sec (0x00)
    Checksum: 0xf7fa [correct]
    [Checksum Status: Good]
    Multicast Address: 239.2.2.2