IS-IS 网络协议 CSNP消息
IS-IS CSNP（Complete Sequence Number PDUs，全时序报文）通过描述全部数据库中的LSP来同步各LSDB（Link-State DataBase），从而维护LSDB，在相邻路由器间保持LSDB的同步。在广播网络上，CSNP由DIS定期发送（缺省的发送周期为10秒）；在点到点链路上，CSNP只在第一次建立邻接关系时发送。
一、 L1/L2 CSNP消息格式
+--------------------------------------------+-------------------
| Intradomain Routing Protocol Discriminator | |
+--------------------------------------------+ |
| Length Indicator | |
+--------------------------------------------+ |
| Version/Protocol ID Extension | |
+--------------------------------------------+ |
| ID Length | |
+--------------------------------------------+ PDU Common
| R | R| R | PDU Type | Header
+--------------------------------------------+ |
| Version | |
+--------------------------------------------+ |
| Reserved | |
+--------------------------------------------+ |
| Maximum Area Address | |
+--------------------------------------------+------------------
| PDU Length | |
+--------------------------------------------+ |
| Source ID | PDU
+--------------------------------------------+ Specific
| Start LSP ID | Header
+--------------------------------------------+ |
| End LSP ID | |
+--------------------------------------------+------------------
| Variable Length Fields |
+--------------------------------------------+
二、 L1/L2 CSNP消息格式各字段含义
| 字段 | 长度 | 含义 |
|---|---|---|
| Intradomain Routing Protocol Discriminator | 1字节 | 域内路由选择协议鉴别符，设置为0x83。 |
| Length Indicator | 1字节 | PDU头部的长度（包括通用头部和专用头部），以字节为单位。 |
| Version/Protocol ID Extension | 1字节 | 版本/协议标识扩展，设置为1（0x01）。 |
| ID Length | 1字节 | NSAP地址或NET中System ID区域的长度。值为0时，表示System ID区域的长度为6字节。值为255时，表示System ID区域为空（即长度为0）。 |
| R | 1比特 | 保留比特位，设置为0。 |
| PDU Type | 5比特 | PDU的类型。
|
| Version | 1字节 | IS-IS版本号，设置为1（0x01）。 |
| Reserved | 1字节 | 保留，设置为0 (0x00)。 |
| Maximum Area Address | 1字节 | 支持的最大区域个数。设置为1～254的整数，表示该IS-IS进程实际所允许的最大区域地址数；设置为0，表示该IS-IS进程最大只支持3个区域地址数。 |
| PDU Length | 2字节 | PDU的总长度，单位是字节。 |
| Source ID | ID Length + 1字节 | 发出CSNP报文的路由器的System ID。 |
| Start LSP ID | ID Length + 2字节 | CSNP报文中第一个LSP的ID值。 |
| End LSP ID | ID Length + 2字节 | CSNP报文中最后一个LSP的ID值。 |
| Variable Length Fields | 变长 |
由多个CLV（Code-Length-Value）三元组组成。CLV也称为TLV（Type-Length-Value）。不同PDU类型所包含的CLV是不同的，其中，Code值从1到10的CLV在ISO 10589中定义（有2类未在上表中列出），其他几种CLV在RFC 1195中定义。 |
三、IS-IS CSNP消息报文示例
Frame 1: 390 bytes on wire (3120 bits), 390 bytes captured (3120 bits)
Arrival Time: May 1, 2015 02:09:24.053266000
Epoch Time: 1430417364.053266000 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: 390 bytes (3120 bits)
Capture Length: 390 bytes (3120 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:llc:osi:isis]
[Coloring Rule Name: Broadcast]
[Coloring Rule String: eth[0] & 1]
IEEE 802.3 Ethernet
Destination: ISIS-all-level-1-IS's (01:80:c2:00:00:14)
Address: ISIS-all-level-1-IS's (01:80:c2:00:00:14)
.... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Source: AlcatelI_2b:c3:d7 (00:20:60:2b:c3:d7)
Address: AlcatelI_2b:c3:d7 (00:20:60:2b:c3:d7)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Length: 376
Logical-Link Control
DSAP: ISO Network Layer (0xfe)
IG Bit: Individual
SSAP: ISO Network Layer (0xfe)
CR Bit: Command
Control field: U, func=UI (0x03)
000. 00.. = Command: Unnumbered Information (0x00)
.... ..11 = Frame type: Unnumbered frame (0x03)
ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol
Intra Domain Routing Protocol Discriminator: ISIS (0x83)
PDU Header Length: 33
Version (==1): 1
System ID Length: 6
PDU Type : L1 CSNP (R:000)
Version2 (==1): 1
Reserved (==0): 0
Max.AREAs: (0==3): 3
ISO 10589 ISIS Complete Sequence Numbers Protocol Data Unit
PDU length: 373
Source-ID: 0020.602b.c3ae.00
Start LSP-ID: 0000.0000.0000.00-00
End LSP-ID: ffff.ffff.ffff.ff-ff
LSP entries (240)
LSP-ID: 0020.602b.0001.00-00, Sequence: 0x0000901a, Lifetime: 563s, Checksum: 0x818b
LSP-ID: : 0020.602b.0001.00-00
LSP Sequence Number : 0x0000901a
Remaining Lifetime : 563s
LSP checksum : 0x818b
LSP-ID: 0020.602b.0002.00-00, Sequence: 0x0002a884, Lifetime: 1143s, Checksum: 0xa245
LSP-ID: : 0020.602b.0002.00-00
LSP Sequence Number : 0x0002a884
Remaining Lifetime : 1143s
LSP checksum : 0xa245
LSP-ID: 0020.602b.0003.00-00, Sequence: 0x0001fa64, Lifetime: 535s, Checksum: 0xc4ad
LSP-ID: : 0020.602b.0003.00-00
LSP Sequence Number : 0x0001fa64
Remaining Lifetime : 535s
LSP checksum : 0xc4ad
LSP-ID: 0020.602b.0004.00-00, Sequence: 0x0000290a, Lifetime: 1052s, Checksum: 0x54a5
LSP-ID: : 0020.602b.0004.00-00
LSP Sequence Number : 0x0000290a
Remaining Lifetime : 1052s
LSP checksum : 0x54a5
LSP-ID: 0020.602b.0005.00-00, Sequence: 0x00028f11, Lifetime: 950s, Checksum: 0x9493
LSP-ID: : 0020.602b.0005.00-00
LSP Sequence Number : 0x00028f11
Remaining Lifetime : 950s
LSP checksum : 0x9493
LSP-ID: 0020.602b.0006.00-00, Sequence: 0x000283c1, Lifetime: 412s, Checksum: 0xccb2
LSP-ID: : 0020.602b.0006.00-00
LSP Sequence Number : 0x000283c1
Remaining Lifetime : 412s
LSP checksum : 0xccb2
LSP-ID: 0020.602b.0007.00-00, Sequence: 0x00026ba5, Lifetime: 901s, Checksum: 0x347f
LSP-ID: : 0020.602b.0007.00-00
LSP Sequence Number : 0x00026ba5
Remaining Lifetime : 901s
LSP checksum : 0x347f
LSP-ID: 0020.602b.0010.00-00, Sequence: 0x0000aacd, Lifetime: 581s, Checksum: 0x1f62
LSP-ID: : 0020.602b.0010.00-00
LSP Sequence Number : 0x0000aacd
Remaining Lifetime : 581s
LSP checksum : 0x1f62
LSP-ID: 0020.602b.0011.00-00, Sequence: 0x000254fc, Lifetime: 601s, Checksum: 0x5f29
LSP-ID: : 0020.602b.0011.00-00
LSP Sequence Number : 0x000254fc
Remaining Lifetime : 601s
LSP checksum : 0x5f29
LSP-ID: 0020.602b.0012.00-00, Sequence: 0x00010e66, Lifetime: 633s, Checksum: 0xebd5
LSP-ID: : 0020.602b.0012.00-00
LSP Sequence Number : 0x00010e66
Remaining Lifetime : 633s
LSP checksum : 0xebd5
LSP-ID: 0020.602b.2f49.00-00, Sequence: 0x18010dae, Lifetime: 541s, Checksum: 0x768a
LSP-ID: : 0020.602b.2f49.00-00
LSP Sequence Number : 0x18010dae
Remaining Lifetime : 541s
LSP checksum : 0x768a
LSP-ID: 0020.602b.2f7f.00-00, Sequence: 0x00007f84, Lifetime: 839s, Checksum: 0x68ec
LSP-ID: : 0020.602b.2f7f.00-00
LSP Sequence Number : 0x00007f84
Remaining Lifetime : 839s
LSP checksum : 0x68ec
LSP-ID: 0020.602b.4ed1.00-00, Sequence: 0x0000dc15, Lifetime: 906s, Checksum: 0xb6f2
LSP-ID: : 0020.602b.4ed1.00-00
LSP Sequence Number : 0x0000dc15
Remaining Lifetime : 906s
LSP checksum : 0xb6f2
LSP-ID: 0020.602b.4ed2.00-00, Sequence: 0x0001f537, Lifetime: 525s, Checksum: 0x7ed2
LSP-ID: : 0020.602b.4ed2.00-00
LSP Sequence Number : 0x0001f537
Remaining Lifetime : 525s
LSP checksum : 0x7ed2
LSP-ID: 0020.602b.4ed3.00-00, Sequence: 0x0001e6de, Lifetime: 833s, Checksum: 0x5b57
LSP-ID: : 0020.602b.4ed3.00-00
LSP Sequence Number : 0x0001e6de
Remaining Lifetime : 833s
LSP checksum : 0x5b57
LSP entries (96)
LSP-ID: 0020.602b.4ed4.00-00, Sequence: 0x000036fc, Lifetime: 651s, Checksum: 0x3adc
LSP-ID: : 0020.602b.4ed4.00-00
LSP Sequence Number : 0x000036fc
Remaining Lifetime : 651s
LSP checksum : 0x3adc
LSP-ID: 0020.602b.4ed5.00-00, Sequence: 0x000110fc, Lifetime: 403s, Checksum: 0x92cd
LSP-ID: : 0020.602b.4ed5.00-00
LSP Sequence Number : 0x000110fc
Remaining Lifetime : 403s
LSP checksum : 0x92cd
LSP-ID: 0020.602b.4ed7.00-00, Sequence: 0x00010c0e, Lifetime: 537s, Checksum: 0xe5c1
LSP-ID: : 0020.602b.4ed7.00-00
LSP Sequence Number : 0x00010c0e
Remaining Lifetime : 537s
LSP checksum : 0xe5c1
LSP-ID: 0020.602b.c3ae.00-00, Sequence: 0x000001fa, Lifetime: 838s, Checksum: 0x39e0
LSP-ID: : 0020.602b.c3ae.00-00
LSP Sequence Number : 0x000001fa
Remaining Lifetime : 838s
LSP checksum : 0x39e0
LSP-ID: 0020.602b.c3ae.02-00, Sequence: 0x00006f18, Lifetime: 838s, Checksum: 0xf2d9
LSP-ID: : 0020.602b.c3ae.02-00
LSP Sequence Number : 0x00006f18
Remaining Lifetime : 838s
LSP checksum : 0xf2d9
LSP-ID: 1720.1603.0250.00-00, Sequence: 0x00003091, Lifetime: 1132s, Checksum: 0xef17
LSP-ID: : 1720.1603.0250.00-00
LSP Sequence Number : 0x00003091
Remaining Lifetime : 1132s
LSP checksum : 0xef17
发表评论