MPLS
, , - (, Frame Relay) .
, MPLS, . (). ( ). MPLS (OSPF, IS-IS, BGP-4) ( MPLS , , , PNNI ). , , , . ,
MPLS, , Frame Relay , . . MPLS (Forwarding Equivalence Class FEC). (VPI/VCI) DLCI Frame Relay. FEC , . , .
. , . , , .
, MPLS . (Forwarding Equivalence Class, FEC), . MPLS, , (Label Switching Router, LSR). , .
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LSR , OSPF, BGP, IS-IS. , , . (Label Distribution Protocol, LDP), (, OSPF, BGP, IS-IS, RSVP .).
LSR MPLS (Label Switching Path, LSP). LSR , , - (FEC), , . , LSR , , . ( FEC .) , , LSP.
. , IP- , .
7.1 MPLS |
MPLS (. 7.1). , MPLS , MPLS. . FEC, , , , , LSR. , , MPLS .
, MPLS IP- , . , LSP , .
FEC IP-, , , , LSP , RSVP . , , MPLS .
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FEC , LSP, ( ). MPLS , . LSR , WRED, WFQ CBWFQ, MPLS .
MPLS IP- , , .
, FEC. .
(Virtual Path Identifier, VPI) (Virtual Circuit Identifier, VCI) ATM. LER (Label Edge Router, LSR-EDGE) , . MPLS . 4.2
32 (4 ): 12 20 .
20- , . 0 2 - 1, ( MPLS IETF).
EXP - 3 . MPLS- IP- (CoS), DiffServ.
TTL (8 ) time-to-live - TTL IP-. , IP- .
, . S - - .
LSR. LSR , (. . 4.1).
, LSR. LSR , , . , , . .
2 3 .
MPLS , . / (push/pop). .
MPLS RFC 3032 MPLS Label Stack Encoding, 2001 . . 7.2 .7.3 .
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7.2
7.3
. 4 . , . MPLS . 32 :
MPLS 2 3. MPLS , , .
, ATM Frame Relay, MPLS- . , ATM MPLS- VPI/VCI, Frame Relay DLCI. , MPLS IP- , MPLS- .
. 4.4, , MPLS 2. MPLS 2, ATM FR, MPLS, Ethernet . IP- 3.
. 7.4 MPLS shim header (-), , 2.5 .
7.4 MPLS
MPLS ( ) , 2. ATM, Frame Relay, PPP, Ethernet, FDDI , MPLS.
, (VCI/VPI ATM, DLCI Frame Relay ..) . IETF MPLS , , , MPLS . MPLS :
ATM, VCI VPI, .4.5;
AAL5 ATM (ATM Adaptation Layer 5) SAR (Segmentation and Reassembly), ATM- , ( MPLS-);
Frame Relay, DLCI (Data Link Connection Identifier), . 4.6;
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4- , (shim), , . 7.7, .
MPLS ATM . 7.5.
7.5 MPLS ATM
ATM (5 ) :
GFC - (4 ) ;
VCI - (16 );
VPI - (8 );
PTI - (3 ):
;
CLP - (1 ): ;
- (8 )
.
MPLS ATM , ATM IP. ATM-, MPLS (ATM-LSR), TCP/IP ATM 53 . MPLS VCI/VPI ATM, MPLS ATM.
MPLS Frame Relay (FR) . ATM, FR-, MPLS, TCP/IP FR. FR DLCI FR. MPLS FR, , FR. MPLS FR Q.922 2 , 4 . . 7.6.
. 7.6 MPLS FR
: DLCI 10,16 24
ATM Frame Relay MPLS , MPLS . , MPLS , , DWDM (Dense Wave Division Multiplexing) , .
, . 7.7, - (Point-to-Point ) Ethernet ( ). MPLS- .
IETF, . , LCP NCR
. 7.7 MPLS- Ethernet
MPLS Ethernet, Ethernet . . MPLS Ethernet, , , MPLS. Ethernet , Ethernet-. Ethernet- 10 /, Ethernet- .
Ethertype Ethernet 8847 8848 . Ethernet, 802.3 LLC/SNAP.
, , 2 3, , , , . , , , , , .
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LSP
7.8 |
(LSP) , (.7.8).. , LSP LSR 0, LSR 1, LSR 3, LSR 4 LSR 5. LSR 0 LSR 5 , , (ingress) (egress) . LSR 1 LSR 3 LSP ; , . , LSP . LSP LSR . , LSR 4 LSR 5 , .
LSP , . , FEC. (ingress, head-end); , LSP, (egress, tail-end).