MPLS Forwarding Control 22 7 Forwarding Equivalence Class

MPLS Forwarding & Control (2/2) 7

Forwarding Equivalence Class (FEC) n A group of IP packets which are forwarded in the same manner (e. g. , over the same path, with the same forwarding treatment) (RFC 3031 Definition) R R IP 1 R IP 2 IP 3 IP 2 R R IP 3 Generally, FEC will cause same forwarding behavior of network. For above network, only considering routing path, IP packet 1&2 belong to same FEC, but IP 3 is in different FEC 12

Label n A short fixed length physically contiguous identifier which is used to identify a FEC, usually of local significance (RFC 3031 Definition) 13

Label Stack Layer 2 Header Label 3 Label 2 Label 1 IP Packet MPLS Domain 1 MPLS Domain 2 MPLS Domain 3 14

Position of MPLS Label 15

LDP & LIB MPLS Label Distribution based on routing table Request: 47. 1 t: 4 ues 1 Req 47. 3 3 2 7. 1 3 . 50 1 2 1 47. 1 3 2 Mapping: 0. 40 g: 0 n i p p Ma LDP: Πρωτόκολλο Κατανομής Ετικέτας (ενημέρωση των LIB) 47. 2 16

Label Swap IP 0. 50 IP 0. 70 1 3 IP 0. 40 2 IP 0. 80 18

MPLS control process (1 of 4) Conventional IP forwarding Control Plane Routing Packets Routing Table Next Hop + Port Packet Classification IP Header Input Packets Queuing and Schedule rules Output Queue Output Packets IP payload User Plane 19

MPLS control process (2 of 4) MPLS Ingress Node Control Plane Label Information Base (LIB) Next Hop + Port Queuing and Schedule rules Routing Packets/Traffic Engineering Parameters FEC to label Map Output Queue Output Packets FEC Classification to FEC Label Push IP Header IP payload Input Packets MPLS Label IP Header IP payload User Plane 20

MPLS control process (3 of 4) MPLS Intermediate Node Control Plane Label Information Base (LIB) Next Hop + Port Queuing and Schedule rules Routing Packets/Traffic Engineering Parameters Incoming Label Map MPLS Label IP Header IP payload Input Packets Output Queue Label Swap Output Packets MPLS Label IP Header IP payload User Plane 21

MPLS control process (4 of 4) MPLS Egress Node Control Plane Label Information Base (LIB) Next Hop + Port Queuing and Schedule rules Routing Packets/Traffic Engineering Parameters Incoming Label Map MPLS Label IP Header IP payload Input Packets Output Queue Output Packets Label Pop IP Header IP payload User Plane 22

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Βιβλιογραφία - Παραπομπές n Go to IETF MPLS WG for RFCs and Ids: http: //www. ietf. org/html. charters/mpls-charter. html ¨ RFCs n n ¨ Internet-Drafts (IDs) n n draft-ietf-mpls-generalized-signaling-02. txt (GMPLS) MPLS resources ¨ ¨ n RFC 2702 Requirements for Traffic Engineering Over MPLS RFC 3031 MPLS Architecture RFC 3032 MPLS Label Stack Encoding RFC 3036 LDP Specification MPLS Resources Center http: //www. mplsrc. com/ MPLS Forum http: //www. mplsforum. com/ The Internet Protocol Journal, Cisco, Volume 4, Number 3, September 2001 ¨ http: //www. cisco. com/ipj 34