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© 2000, Cisco Systems, Inc. 3-1 Chapter 3 Label Distribution Protocol.

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1 © 2000, Cisco Systems, Inc. 3-1 Chapter 3 Label Distribution Protocol

2 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-2 Objectives Upon completion of this chapter, you will be able to perform the following tasks: Explain the mechanics of Label Distribution Protocol Demonstrate how labels are assigned, distributed,..encoded and discovered Identify Show and Config commands used in Label..Distribution Protocol Identify the Debug commands used in Label Distribution..Protocol

3 © 2000, Cisco Systems, Inc Label Distribution Protocol Overview

4 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-4 Label Switching Control Plane FIB LFIB UnLabelged Pkt Labelged Pkt UnLabelged Pkt Labelged Pkt UnLabelged Pkt Labelged Pkt R1R2

5 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-5 Label Control Plane Populates LIB and LFIB Label Information Base (LIB) Label Forwarding Information Base (LFIB) Label Distribution In LabelOut LabelInterface tR1tR2i3 DestinationIn Label(Peer, Out Label),… DtR1 (R2:0, tR2), R3:0, tR3), (R4:0, tR4)

6 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-6 Label Distribution Terminology P dest D Label for D Upstream Platform Downstream Platform P dest D Label for D Upstream Platform Downstream Platform RuRd RuRd

7 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-7 Label Assignment Assignment of incoming (local) Labels: –Per Interface: For interfaces that use interface resources for Labels –Per Platform: For interfaces that share the same Labels

8 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-8 Downstream Label Distribution Variants Downstream Downstream on Demand Label for D P Destination D Upstream LSR Downstream LSR RuRd

9 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-9 Label Distribution Possibilities Dynamic Label Switching –Enhance routing protocol to carry Labels –Use protocol designed to distribute Labels For TSP Tunnels –Enhance RSVP to carry Labels –Use protocol designed to distribute Labels

10 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-10 Label Distribution Protocol (LDP) Runs in parallel with routing protocols Distributes bindings Incremental updates over TCP Other Label distribution mechanisms can run in parallel with it

11 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-11 LDP Identifier Identifies Label space 6 bytes Cisco convention –a.b.c.d:n a b c d n Router IDLabel Space ID

12 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-12 LDP Sessions and Label Spaces LDP sessions support Label exchange between LSRs Design choice is to use one Label space per LDP session rather than many Label spaces per LDP session

13 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-13 Link Topology and LDP Sessions L2L4 L1L3 Topology: LDP Sessions: L1 L2 L3 R1 R2 R1 R2 R4 R3 Session for L1 Session for L3 Session for L2Session for L4 R1 R2 R4 R3 Session for L1, L2, L3 R1 R2

14 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-14 Link Topology and LDP Sessions (cont.) Topology: LDP Sessions: L2(ATM) L1(ATM) Session for L2 Session for L1 R1R2 R1R2 L1 L2(ATM) L3 Session for L1, L3 Session for L2 R1R2 R1R2

15 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-15 LDP Transport Uses TCP for reliable transport Well-known contact port (711) Design Choice: One LDP session per TCP connection

16 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-16 LDP Discovery LSRs learn Label neighbors via LDP discovery ? ? ? Hello, T1:0Hello, T1:1 Hello, T1:0 ?? atm Hello, T2:3 Hello, T3:0 Hello, T4:0 ? ? ??? T4:0T3:0 T1T2:3T1

17 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-17 LDP Sessions and Keep Alives LDP monitors health and necessity of sessions Keep Alive PIEs monitor integrity of transport connection Discovery Hello PDUs signal peer willingness to Label switch on link

18 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-18 LDP Identifiers and Next Hop Addresses LIB stores Labels with peer LDP Identifiers Routing maintains next-hop IP addresses Dest In Label (Peer, Out Label),… Dt R1 (R 2 :0, t R2 ), (R 3 :0, t R3 ), (R 4 :0, t R4 ) DestNext HopInterfacePctlMetric Da.b.c.di 3 OSPF100 LIBRouting Table

19 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-19 LDP Identifiers and Next Hop Addresses (cont.) LFIB requests Label assigned by next-hop for destination LIB maps next-hop address to peer LDP identifier to retrieve Label LSRs: –Advertise interface addresses via LDP –Build peer LDP identifer Address Map from learned addresses

20 © 2000, Cisco Systems, Inc Label Distribution Protocol Mechanics © 1999, Cisco Systems, Inc

21 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-21 Label Assignment Assignment of incoming (local) Labels: Per Interface: For interfaces that use interface resources for Labels Per Platform: For interfaces that share the same Labels

22 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-22 Label Distribution Protocol (LDP) Runs in parallel with routing protocols Distributes bindings Incremental updates over TCP Other Label distribution mechanisms can run in parallel with it

23 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-23 LDP Identifier Identifies Label space 6 bytes Cisco convention –a.b.c.d:n a b c d n Router IDLabel Space ID

24 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-24 LDP Sessions and Label Spaces LDP sessions support Label exchange between LSRs Design choice is to use one Label space per LDP session rather than many Label spaces per LDP session

25 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-25 Link Topology and LDP Sessions Topology: LDP Sessions: L2(ATM) L1(ATM) Session for L2 Session for L1 R1R2 R1R2 L1 L2(ATM) L3 Session for L1, L3 Session for L2 R1R2 R1R2

26 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-26 LDP Encoding LDP TCP connection carries protocol data units (PDUs) PDU carries one or more protocol information elements (PIEs) Type-Length-Value (TLV) encoding provides extensibility 1230 PIE Len PIE DataPIE TypePIE Len PDU Len Ptcl VerPDU LenResPIE 1PIE 2PIE nLDP ID 1230 TLV Len ValueTypeLen

27 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-27 LDP Protocol Information Elements (PIEs) LDP PIE s include: Open Bind, Request Bind, Withdraw Bind Address, Withdraw Address Keep Alive

28 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-28 LDP Discovery LSRs learn Label neighbors via LDP discovery ? ? ? Hello, T1:0Hello, T1:1 Hello, T1:0 ?? atm Hello, T2:3 Hello, T3:0 Hello, T4:0 ? ? ??? T4:0T3:0 T1T2:3T1 (Corrected Slide)

29 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-29 Discovery Triggers LDP Session Establishment Receive Hello T2:0 on link Open LDP TCP connection to T2 Negotiate session parameters via Open PIEs T1:0T2:0 Hello, T2:0 Hello, T1:0 Link L

30 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-30 LDP Sessions and Adjacencies LDP session = 1 transport adjacency + 1 or more link adjacencies LDP Session with T2 - 1 transport adjacency - 1 link adjacency LDP session with T2 - 1 transport adjacency - 3 link adjacencies T1 T2 T1 Link L Link L 1 Link L 2 Link L 3 T2

31 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-31 LDP Sessions and Keep Alives LDP monitors health and necessity of sessions Transport adjacency. Keep Alive PIEs monitor integrity of transport connection Link adjacency. Discovery Hello PDUs signal peer willingness to Label switch on link

32 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-32 LDP Sessions Between Non- Directly Connected LSRs BGP Egress Router Normally Routed Path Traffic Engineering Route R9 R8R7R6 R5 R4 R3 R2 R1

33 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-33 LDP Directed Hellos Extend LDP Discovery to non-directly connected LSRs Differ from normal Hello’s –Sent to specific address –Initiator solicits Directed Hello’s from target

34 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-34 Populating the LFIB with Labels LIB holds –Labels locally assigned –Labels learned from LDP peers LFIB updates triggered by –Routing changes –Label advertisements from peers LFIB LIB LDP LDP Bind PIE (D, Label) add_Label(LDP_id, D, Label) find_route_Labels(D, next_hop) route_Label_change (D, next_hop, inLabel, outLabel) Routing Change (D, next_hop) Routing

35 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-35 Label Distribution Mechanics: Downstream Method Distributes per-platform Label space Supporting data structures: –LIB –Label Distribution Peer Database Periodic scan of data structures finds peers that need Label advertisements

36 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-36 D6 seq 3 t2 D3 seq 4 t4 D1 seq 8 t6 D2 seq 11 t10 D4 seq 17 t13 Label Distribution Mechanics: Downstream Method Example Start of update list End of update list radix tree Label Distribution Peer Database LIB D5 seq 21 t16 R1:0 seq 8 R1:0 seq 8 R2:0 seq 3 R3:0 seq 21 R3:0 seq 21

37 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-37 Label Distribution Mechanics: Downstream on Demand Distributes per-interface Label space (e.g. Label Controlled ATM) Upstream LSR requests Label for specific destination from downstream LSR Builds Label VC from Head End platform to Tail End platform

38 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-38 Label Distribution Mechanics Downstream on Demand Example Head End Tail End Label VC... D Request Bind (D) S1S2 S1S2 Bind (D, Label ) S1 Bind (D, Label ) S2 Bind (D, Label ) R2 R1

39 © 2000, Cisco Systems, Inc LDP Show & Config Commands © 1999, Cisco Systems, Inc

40 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-40 LDP Show Commands Example Network ether1/1/1 ether1/1/2 ether4/0/1 atm0/0/3 atm1/0atm0/0/1atm3/0atm0/0/1 atm0/0/2atm0/0atm0/0/2atm0/0/0atm0/0atm0/0/0 S2 S7 R9 R8

41 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-41 Show LDP Parameters Labelsw-r9#show Label-switching LDP parameters Protocol version: 1 Downstream Label pool: min Label: 10; max_Label: 10000; reserved Labels:16 Session hold time: 30 sec; keep alive interval: 10 sec Discovery hello: holdtime: 20 sec; interval: 4 sec Discovery directed hello: holdtime: 15 sec; interval: 5 sec Labelsw-r9#

42 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-42 Show LDP Discovery Information Labelsw-r8# show Label-switching LDP discovery Local LDP Identifier: :0 LDP Discovery Sources: Interfaces: ATM0/0.1: xmit/recv LDP Id: :2 Ethernet1/1/1: xmit/recv LDP Id: :0 Ethernet1/1/2: xmit/recv LDP Id: :0 ATM3/0.1: xmit/recv LDP Id: :1 Labelsw-r8#

43 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-43 LDP Neighbor Information: LS1010 Example Labelsw1010-7#show Label-switching LDP neighbor Peer LDP Ident: :2; Local LDP Ident :1 TCP connection: State: Oper; PIEs sent/rcvd: 20852/20863; Downstream on demand Up time: 1d01h LDP discovery sources: ATM0/0/0 Peer LDP Ident: :1; Local LDP Ident :2 TCP connection: State: Oper; PIEs sent/rcvd: 20846/20868; Downstream on demand Up time: 1d01h LDP discovery sources: ATM0/0/1 Peer LDP Ident: :3; Local LDP Ident :3 TCP connection: State: Oper; PIEs sent/rcvd: 20849/20867; Downstream on demand Up time: 1d01h LDP discovery sources: ATM0/0/2 Peer LDP Ident: :4; Local LDP Ident :4 TCP connection: State: Oper; PIEs sent/rcvd: 20846/20829; Downstream on demand Up time: 1d01h LDP discovery sources: ATM0/0/3 Labelsw1010-7#

44 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-44 LDP Label Binding Information: Router Labelsw-r8#show Label-switching LDP neighbor PeerLDP Ident: :1; Local LDP Ident :2 TCP connection: State: Oper; PIEs sent/rcvd: 20859/20848; Downstream on demand Up time: 1d01h LDP discovery sources: ATM3/0.1 PeerLDP Ident: :2; Local LDP Ident :1 TCP connection: State: Oper; PIEs sent/rcvd: 20864/20843; Downstream on demand Up time: 1d01h LDP discovery sources: ATM0/0.1 PeerLDP Ident: :0; Local LDP Ident :0 TCP connection: State: Oper; PIEs sent/rcvd: 20831/20849; Downstream Up time: 1d01h LDP discovery sources: Ethernet1/1/2 Ethernet1/1/1 Addresses bound to peer LDP Ident: Labelsw-r8#

45 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-45 LDP Label Binding Information: Router (cont.) Labelsw-r8#show Label-switching LDP binding Matching entries: LIB entry: /32, rev 25 remote binding: LSR: :0, Label: 26 LIB entry: /16, rev 26 remote binding: LSR: :0, Label: 27 LIB entry: /16, rev 27 remote binding: LSR: :0, Label: 28 LIB entry: /16, rev 7 local binding: Label: 26 remote binding: LSR: :0, Label: 29 LIB entry: /16, rev 6 local binding: Label: imp-null(1) remote binding: LSR: :0, Label: imp-null(1)... Labelsw-r8#

46 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-46 LDP Session Hold Time Labelsw-r8(config)#Label-switching LDP holdtime ? Holdtime in seconds Labelsw-r8(config)# Label Range for Label Switching Labelsw-r8(config)#Label-switching Label-range downstream Labelsw-r8(config)# Label Switching Configuration

47 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-47 LDP Discovery Labelsw-r8(config)#Label-switching LDP discovery ? directed-hello LDP discovery Directed Hello hello LDP discovery Hello Labelsw-r8(config)# Labelsw-r8(config)#Label-switching LDP discovery hello ? holdtime LDP discovery Hello holdtime interval LDP discovery Hello interval Labelsw-r8(config)# Labelsw-r8(config)#Label-switching LDP discovery directed-hello ? holdtime LDP discovery Directed Hello holdtime interval LDP discovery Directed Hello interval Labelsw-r8(config)

48 © 2000, Cisco Systems, Inc LDP Debug Commands © 1999, Cisco Systems, Inc

49 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-49 Summary of LDP Debug Commands router#debug Label LDP ? advertisementsLDP Label and address advertisements bindingsLabel bindings and other Label Information Base (LIB) changes peerLDP peer piesLDP Protocol Information Elements sessionLDP session LabelconLabel control process transportLDP transport and discovery

50 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-50 router#debug Label LDP advertisements Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise Labelcon:adj :0 (pp 0x60D428E8): advertise /16,Label 1(#7) Labelcon:adj :0 (pp 0x60D428E8): advertise /16,Label 1(#8). Labelcon:adj :0 (pp 0x60D428E8):advertise /16,Label 28(#18) Labelcon:adj :0 (pp 0x60D428E8):advertise /32, Label 29(#20)

51 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-51 router#debug Label LDP bindings Labelcon: libent( /32): created; find route Labels request Labelcon: libent( /32): lcl Label 26 (#2) assigned Labelcon: libent( /32): created; find route Labels request Labelcon: libent( /32): lcl Label 27 (#4) assigned Labelcon: libent( /32): created; find route Labels request Labelcon: libent( /32): lcl Label 28 (#6) assigned Labelcon: :0: added to addr LDP ident map Labelcon: :0: added to addr LDP ident map Labelcon: libent( /32): rem Label 28 from :0 added... Labelcon: libent( /32): deleted Labelcon: libent( /32): deleted

52 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-52 router#deb Label LDP peer state-machine Labelcon: start LDP TCP timers for :1 (pp 0x60F28FF8) Labelcon: adj :1-1 (pp 0x60F28FF8): Event unsol open unsol op pdg -> estab Labelcon: adj :0 (pp 0x60F1DEA4): Event down estab -> dstroy Labelcon: adj :0 (pp 0x60F1DEA4): Event cleanup done dstroy -> non-ex Labelcon: adj :1 (pp 0x60F28FF8): Event down estab -> dstroy Labelcon: adj :1 (pp 0x60F28FF8): Event cleanup done dstroy -> non-ex Labelcon: start LDP TCP timers for :1 (pp 0x60EBB9AC) Labelcon: adj :1-1 (pp 0x60EBB9AC): Event unsol open unsol op pdg -> estab

53 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-53 router#debug Label LDP pies received [all] LDP: Rcvd open PIE from (pp 0x0) LDP: Rcvd keep_alive PIE from :0 (pp 0x0) LDP: Rcvd bind PIE from :0 (pp 0x60ECC094) LDP: Rcvd notification PIE from :0 (pp 0x60ECC094) LDP: Rcvd address PIE from :0 (pp 0x60ECC094)

54 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-54 router#debug Label LDP pies sent [all] LDP: Queued open PIE to (pp 0x0) LDP: Sent open PIE to (pp 0x0) LDP: Queued keep_alive PIE to :0 (pp 0x0) LDP: Sent keep_alive PIE to :0 (pp 0x0) LDP: Queued address PIE to :0 (pp 0x60ECC094) LDP: Sent address PIE to :0 (pp 0x60ECC094) LDP: Queued bind PIE to :0 (pp 0x60ECC094) LDP: Sent bind PIE to :0 (pp 0x60ECC094)

55 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-55 router#debug Label LDP session io [all] LDP: Rcvd open PIE from (pp 0x0) --LDP open PIE: PDU hdr: LDP Id: :0; PIE Contents: 0x00 0x01 0x00 0x10 0xAB 0x45 0xCC 0xEA 0x00 0x00 0x00 0x00 0x01 0x00 0x00 0x04 0x01 0x00 0x00 0x0F LDP: Sent keep_alive PIE to :0 (pp 0x0) --LDP keep_alive PIE: PDU hdr: LDP Id: :0; PIE Contents: 0x00 0x01 0x00 0x0C 0xAC 0x1B 0x20 0x1C 0x00 0x00 0x00 0x00 0x05 0x00 0x00 0x00 LDP: Rcvd keep_alive PIE from :0 (pp 0x0) --LDP keep_alive PIE: PDU hdr: LDP Id: :0; PIE Contents: 0x00 0x01 0x00 0x0C 0xAB 0x45 0xCC 0xEA 0x00 0x00 0x00 0x00 0x05 0x00 0x00 0x00 LDP: Sent address PIE to :0 (pp 0x60D6D884) --LDP address PIE: PDU hdr: LDP Id: :0; PIE Contents: 0x00 0x01 0x00 0x30 0xAC 0x1B 0x20 0x1C 0x00 0x00 0x00 0x00 0x08 0x00 0x00 0x24 0x00 0x01 0x00 0x03 0x00 0x1E 0x20 0x63 0x65 0x00 0x08 0x20 0xAC 0x1B 0x20 0x1C 0x20 0x0A 0x69 0x00 0x08 0x20 0x0A 0x5C 0x00 0x08 0x20 0x0A 0xCD 0x00 0x08 0x20 0xd2 0x08 0x00 0x08

56 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-56 router#debug Label LDP session state-machine LDP: adj: (0x60E0E034): Event: Xport opened; Non-existent -> Init pasv LDP: LDP_create_ptcl_adj: tp = 0x60E0E034, ipaddr = LDP: adj: (0x60E0E034): Event: Xport opened; Init pasv -> Init pasv LDP: adj: (0x60E0E034): Event: Rcv LDP Open; Init pasv -> Open rcvd pasv LDP: adj: (0x60E0E034): Event: Rcv LDP KA; Open rcvd pasv -> Oper LDP: adj:unknown(0x60E0E034): Event: Xport closed; Oper -> Non-existent

57 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-57 router#debug Label LDP transport connections Debug output at active peer: LDP: Opening conn; adj 0x60D3AC50, LDP: Conn is up; adj 0x60D3AC50, : :7110 LDP: Conn closed by peer; adj 0x60D3AC : :711, Ethernet4/0/1 LDP: Closing conn : :711, adj 0x60D3AC50 Debug output at passive peer: LDP: Incoming conn : :11164 LDP: Conn closed by peer; adj 0x60D0B8B : :11164, Ethernet1/1/2 LDP: Closing conn : :11164, adj 0x60D0B8B8

58 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-58 router#debug Label LDP transport events LDP: LDP_set_intf_id: intf 0x60D40D50, Ethernet1/1/1, not tc-atm, intf_id 0 LDP: Rcvd hello; Ethernet1/1/1, from ( :0), intf_id 0, opt 0x4 LDP: Hello from ( :0) to , opt 0x4 LDP: New adj 0x60D3852C from ( :0), Ethernet1/1/1 LDP: Ignore Hello Timer for Ethernet1/1/1; intf not LDP ready LDP: Send hello; Ethernet1/1/1, src/dst / , inst_id 0 LDP: Incoming conn : :11166 LDP: Found adj 0x60D3852C for (Hello xport addr opt) LDP: New temporary adj 0x60D385D8 from LDP: Real adj 0x60D3852C bound to :0, replacing temp adj 0x60D385D8 LDP: Adj 0x60D385D8; state set to closed LDP: Rcvd hello; Ethernet1/1/1, from ( :0), intf_id 0, opt 0x4... Labelsw-r8#conf t Labelsw-r8(config)#int ether 1/1/1 Labelsw-r8(config)#no Label ip... LDP: Ignore Hello from , Ethernet1/1/1; no intf LDP: Hold timer expired for adj 0x60D3852C, will close conn LDP: Closing conn : :11166, adj 0x60D3852C LDP: Adjacency 0x60D3852C, timed out LDP: Adj 0x60D3852C; state set to closed LDP: Ignore Hello from , Ethernet1/1/1; no intf router#...

59 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-59 Label Distribution Protocol Summary LDP runs in parallel with routing protocols Used to distribute bindings Incremental updates over TCP Other Label distribution mechanisms can run in parallel with LDP

60 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-60 Summary After completing this chapter, you should be able to perform the following tasks: Explain the mechanics of Label Distribution Protocol Demonstrate how labels are assigned, distributed, encoded and discovered Identify Show and Config commands used in Label Distribution Protocol Identify the Debug commands used in Label Distribution Protocol

61 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-61 Review Questions 1. What are some of the features of Label Distribution Protocol? 2. In Link Adjacency, what causes an LSR to terminate a link? 3. What function do Keep-Alive PIEs perform? 4. How does the discovery process trigger an LDP session to be created? 5. How are Directed Hellos different from Normal Hellos?

62 © 2000, Cisco Systems, Inc. CMPLS 1.0—3-62 Review Questions (cont.) 6. What events trigger updates to the Label Forwarding Information Base (LFIB)? 7. What command do you use to get detailed information on the number of PIEs sent and received on all LDP discovery sources? 8. What purpose do LDP configuration commands serve? 9. What debug command lists a summary of all LDP Debug commands?


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