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OSPF IS-IS
Intermediate System to Intermediate System (IS-IS IS to IS) 1978 .
Open Shortest Path First (OSPF) IS-IS, IPv4. 1989 OSPF Internet Engineering Task Force, OSPFv2, , 1998 RFC2328. OSPF, , , IS-IS . , ( ).
1993 Novell, , IS-IS Netware. Novell, Internet Packet Exchange (IPX), , (EIGRP, IPX). IS-IS. Novell, IS-IS, . IS-IS -, , RIP, IS-IS OSPF.
Intermediate System to Intermediate System Protocol
Intermediate System to Intermediate System (IS-IS) Intermediate System ( (IS), - End System ( (ES). , , , . (Network Service Access Point - NSAP), . , IP, IS-IS . End System to Intermediate System (ES-IS), IS-IS , , .
IS-IS - . . IS-IS, IP . IS-IS, , . , . , , .
OSI
IS-IS , Internet Protocol (IP) . (Open Systems Interconnect - OSI) , . OSI , , , , , , (N-). OSI , . IP .
- Authority Format Identifier (AFI), Initial Domain Identifier (IDI), High-Order Domain Specific Part (HO-DSP) , .
- - .
- N Selector, NSAP, ( , NSAP, ).
, , 1.
1:
- . , , .
- N- , . , A N-, 49.0011.2222.0000.0000.000A.00.
- N-, N- , .
- A B flooding , .
- C D flooding domain.
- A D , . IS-IS ( , ).

, IP, IS-IS . , , . , (SPF).
IS-IS
IS-IS . IS :
- Hello-
- (PSNP CSNP)
- (Link State Packet - LSP)
LSP IS, , IS. LSP Type Length Vectors (TLV), . TLV :
- 2 22:
- 128, 135 235: IPv4
- 236 237: IPv6
, , IS-IS 6- ( 8 , , , , ). , , , 24 - 32- , .
LSP, IS, IPv4 IPv6, , , MPLS , MTU. IS-IS LSP . . , , LSP. IS-IS , .
IS-IS , ES-IS, IS-IS IP, , IP, . . , IS-IS - , , .
IS-IS . 2 .
2:
- IS A B. , , . (hold time) B A, (MTU) . . MTU .
- IS B A. , , A. A B. MTU .
- A B, A B .
- A B , B A .
- B , (B LSP, ). Complete Sequence Number Packet (CSNP).
- A , , B. (LSP), , B Partial Sequence Number Packet (PSNP).
- B PSNP, Send Route Message (SRM) (LSP), A.
- SRM. , A B.
. , RFC5303, , , 2005 .

SRM , ?
.
SPF ( SPF) IS flooding domain . . IS-IS , ? point-to-point . , flooding domain (, Ethernet).
IS-IS LSP, , . 3 .

3:
- (packet length) . , 15 , 15 . 2 , 65 536 - , MTU .
- (remaining lifetime) , LSP . , LSP, , , , , . , , , , IS , IS. , . 65 536 - - 1092 , 18 . LSP 18 .
- LSP ID LSP. , , , ( ) LSP, , , LSP. , LSP, . LSP - IS. 8 .
- (Sequence Number) LSP. , IS . , ( ) .
- (Checksum) , , LSP, .
4.

4:
- 2001: db8: 3e8: 100 :: / 64. A , .
- A SRM B.
- - ( ) SRM.
- , B CSNP, , A.
- CSNP, A SRM B.
- B . , , . , , B C.
? IS-IS flooding:
- IS .
- - , IS (lifetime) 0 . , IS zero age SPF.
- lifetime IS, zero age . IS, zero age, , ( ), . .
IS CNSP , , . , , .
IS-IS
IS-IS :
- flooding domain ( ).
- loop-free - SPF .
- ( ).
- .
- (lifetime) .
- MTU .
- , , .
IS-IS - , .