PIM Hello报文格式

PIM Hello报文格式
PIM路由器之间通过交互Hello消息，发现PIM邻居并维护邻居关系。Hello消息同时在PIM-DM与PIM-SM中使用。Hello消息中无法区分是PIM-DM还是PIM-SM。
一、PIM Hello消息格式

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-------+-------+---------------+-------------------------------+
   |PIM Ver| Type  |   Reserved    |           Checksum            |
   +-------+-------+---------------+-------------------------------+
   |          OptionType           |         OptionLength          |
   +-------------------------------+-------------------------------+
   |                          OptionValue                          |
   |                              ...                              |
   +---------------------------------------------------------------+
   |                               .                               |
   |                               .                               |
   |                               .                               |
   +-------------------------------+-------------------------------+
   |          OptionType           |         OptionLength          |
   +-------------------------------+-------------------------------+
   |                          OptionValue                          |
   |                              ...                              |
   +---------------------------------------------------------------+

二、PIM Hello消息格式解释

字段	长度	说明
PIM Ver	4比特	PIM版本，值为2。
Type	4比特	消息类型，值为0。
Reserved	8比特	保留字段，发送时设置为0，接收时忽略此值。
Checksum	16比特	校验和。
OptionType	2字节	Option参数类型。参数类型对应的参数名： 1: Holdtime，表示保持邻居为可达状态的超时时间，若超时仍没有收到Hello消息则认为邻居不可达。 2: LAN Prune Delay，由三部分组成： +-+-------------------+-------------------+ \|T\| Propagation_Delay \| Override_Interval \| +-+-------------------+-------------------+ T：1比特，Join消息抑制能力位。 Propagation_Delay：15比特，表示在共享网段上传递Prune消息的延迟时间。 Override_Interval：16比特，在共享网段上执行剪枝前的否决时间。 3 - 16：预留为将来使用。 18：预留不用。 19: DR Priority，表示各路由器接口竞选DR的优先级，优先级越高越容易获胜。 20: Generation ID，Hello消息中携带的随机数，表示当前邻居状态。如果状态发生更新则随机数也会更新。当路由器发现接收到的来自上游的Hello消息中包含不同Generation ID值，则认为上游邻居已经丢失或上游邻居状态已经改变。 21: State Refresh Capable，表示邻居状态刷新时间间隔。 24: Address List，PIM接口的从地址列表。
OptionLength	2字节	OptionValue字段的长度，字节为单位。
OptionValue	可变	Option参数值。

三、PIM Hello消息（IPv4）报文示例

Frame 1: 68 bytes on wire (544 bits), 68 bytes captured (544 bits)
    Encapsulation type: Ethernet (1)
    Arrival Time: Jul 16, 2009 00:04:01.029410000
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1247673841.029410000 seconds
    [Time delta from previous captured frame: 0.000000000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Frame Length: 68 bytes (544 bits)
    Capture Length: 68 bytes (544 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:pim]
    [Coloring Rule Name: Broadcast]
    [Coloring Rule String: eth[0] & 1]
Ethernet II, Src: 00:16:9c:6e:7a:40 (00:16:9c:6e:7a:40), Dst: IPv4mcast_0d (01:00:5e:00:00:0d)
    Destination: IPv4mcast_0d (01:00:5e:00:00:0d)
        Address: IPv4mcast_0d (01:00:5e:00:00:0d)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: 00:16:9c:6e:7a:40 (00:16:9c:6e:7a:40)
        Address: 00:16:9c:6e:7a:40 (00:16:9c:6e:7a:40)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IP (0x0800)
Internet Protocol Version 4, Src: 10.20.7.54 (10.20.7.54), Dst: 224.0.0.13 (224.0.0.13)
    Version: 4
    Header Length: 20 bytes
    Differentiated Services Field: 0xc0 (DSCP 0x30: Class Selector 6; ECN: 0x00: Not-ECT (Not ECN-Capable Transport))
        1100 00.. = Differentiated Services Codepoint: Class Selector 6 (0x30)
        .... ..00 = Explicit Congestion Notification: Not-ECT (Not ECN-Capable Transport) (0x00)
    Total Length: 54
    Identification: 0xb636 (46646)
    Flags: 0x00
        0... .... = Reserved bit: Not set
        .0.. .... = Don't fragment: Not set
        ..0. .... = More fragments: Not set
    Fragment offset: 0
    Time to live: 1
    Protocol: PIM (103)
    Header checksum: 0x6f13 [validation disabled]
        [Good: False]
        [Bad: False]
    Source: 10.20.7.54 (10.20.7.54)
    Destination: 224.0.0.13 (224.0.0.13)
    [Source GeoIP: Unknown]
    [Destination GeoIP: Unknown]
Protocol Independent Multicast
    0010 .... = Version: 2
    .... 0000 = Type: Hello (0)
    Reserved byte(s): 00
    Checksum: 0xd026 [correct]
    PIM options: 4
        Option 1: Hold Time: 105s 
            Type: 1
            Length: 2
            Holdtime: 105s 
        Option 20: Generation ID: 3620
            Type: 20
            Length: 4
            Generation ID: 3620
        Option 19: DR Priority: 1
            Type: 19
            Length: 4
            DR Priority: 1
        Option 21: State Refresh Capable: Version = 1, Interval = 0s
            Type: 21
            Length: 4
            Version: 1
            Interval: 0
            Reserved: 0

四、PIM Hello消息（IPv6）报文示例

Frame 1: 118 bytes on wire (944 bits), 118 bytes captured (944 bits)
    Encapsulation type: Ethernet (1)
    Arrival Time: Apr  7, 2010 11:55:07.000000000
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1270612507.000000000 seconds
    [Time delta from previous captured frame: 0.000000000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Frame Length: 118 bytes (944 bits)
    Capture Length: 118 bytes (944 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:vlan:ethertype:ipv6:ipv6.nxt:pim]
    [Coloring Rule Name: Broadcast]
    [Coloring Rule String: eth[0] & 1]
Ethernet II, Src: 00:e0:fc:00:29:d8 (00:e0:fc:00:29:d8), Dst: IPv6mcast_0d (33:33:00:00:00:0d)
    Destination: IPv6mcast_0d (33:33:00:00:00:0d)
        Address: IPv6mcast_0d (33:33:00:00:00:0d)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: 00:e0:fc:00:29:d8 (00:e0:fc:00:29:d8)
        Address: 00:e0:fc:00:29:d8 (00:e0:fc:00:29:d8)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 6, CFI: 0, ID: 8
    110. .... .... .... = Priority: Voice, < 10ms latency and jitter (6)
    ...0 .... .... .... = CFI: Canonical (0)
    .... 0000 0000 1000 = ID: 8
    Type: IPv6 (0x86dd)
    Trailer: acf6471a
Internet Protocol Version 6, Src: fe80::2e0:fcff:fe00:29d8 (fe80::2e0:fcff:fe00:29d8), Dst: ff02::d (ff02::d)
    0110 .... = Version: 6
        [0110 .... = This field makes the filter "ip.version == 6" possible: 6]
    .... 0000 0000 .... .... .... .... .... = Traffic class: 0x00000000
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Field: Default (0x00000000)
        .... .... ..0. .... .... .... .... .... = ECN-Capable Transport (ECT): Not set
        .... .... ...0 .... .... .... .... .... = ECN-CE: Not set
    .... .... .... 0000 0000 0000 0000 0000 = Flowlabel: 0x00000000
    Payload length: 56
    Next header: PIM (103)
    Hop limit: 1
    Source: fe80::2e0:fcff:fe00:29d8 (fe80::2e0:fcff:fe00:29d8)
    [Source SA MAC: 00:e0:fc:00:29:d8 (00:e0:fc:00:29:d8)]
    Destination: ff02::d (ff02::d)
    [Source GeoIP: Unknown]
    [Destination GeoIP: Unknown]
Protocol Independent Multicast
    0010 .... = Version: 2
    .... 0000 = Type: Hello (0)
    Reserved byte(s): 00
    Checksum: 0x45a1 [correct]
    PIM options: 5
        Option 1: Hold Time: 105s 
            Type: 1
            Length: 2
            Holdtime: 105s 
        Option 19: DR Priority: 1
            Type: 19
            Length: 4
            DR Priority: 1
        Option 20: Generation ID: 461646429
            Type: 20
            Length: 4
            Generation ID: 461646429
        Option 2: LAN Prune Delay: T = 0, Propagation Delay = 500ms, Override Interval = 2500ms
            Type: 2
            Length: 4
            0... .... = T: False
            .000 0001 1111 0100 = Propagation Delay: 500
            Override Interval: 2500
        Option 24: Address List
            Type: 24
            Length: 18
            Address List (24)
                Address: 2000::10 (2000::10)

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