MPLS Multi-protocol label switching Mario Baldi Politecnico di Torino (Technical University of Torino)

Transcription

1 MPLS Multi-protocol label switching Mario Baldi Politecnico di Torino (Technical University of Torino) MPLS - 1

2 MPLS - 2 Copyright notice This set of transparencies, hereinafter referred to as slides, is protected by copyright laws and provisions of International Treaties. The title and copyright regarding the slides (including, but not limited to, each and every image, photography, animation, video, audio, music and text) are property of the authors specified on page 1. The slides may be reproduced and used freely by research institutes, schools and Universities for non-profit institutional purposes. In such cases, no authorization is requested. Any total or partial use or reproduction (including, but not limited to, reproduction on magnetic media, computer networks, and printed reproduction) is forbidden, unless explicitly authorized by the authors by means of written license. Information included in these slides is deemed as accurate at the date of publication. Such information is supplied for merely educational purposes and may not be used in designing systems, products, networks, etc. In any case, these slides are subject to changes without any previous notice. The authors do not assume any responsibility for the contents of these slides (including, but not limited to, accuracy, completeness, enforceability, updated-ness of information hereinafter provided). In any case, accordance with information hereinafter included must not be declared. In any case, this copyright notice must never be removed and must be reported even in partial uses.

3 From MPLS Forum Documents MPLS is the enabling technology for the New Broadband (IP) Public Network MPLS - 3

4 The onion that makes telecos cry IP over ATM IP Leased Line Frame Relay ATM Circuit Emulation ATM WDM IP over DWDM IP over Frame Relay IP ATM IP MPLS - 4 IP over SONET/SDH IP over ATM Circuit Emulation

5 The future: WDM, IP, MPLS IP router with LAN or WAN interface IP IP router with T3 interface PABX with T1 interface IP router with LAN (GE) or WAN (PoS) Interface λ Switching IP/MPLS MPLS - 5

6 The idea Label IP packet Forwarding packets according to a label Instead of the IP destination address MPLS - 6

7 Why? Faster lookup The label may be used as an index Instead of longest prefix matching Traffic engineering MPLS - 7

8 MPLS introduces a connection-oriented paradigm in IP networks MPLS - 8

9 Network architecture MPLS network MPLS cloud Label switch router (LSR) Label edge router Ingress/egress LSR MPLS - 9

10 Label Switched Path (LSP) Ingress LSR Egress LSR MPLS - 10

11 Label switching A D X D In Out In 0 1 Out In 0 1 Out In Out D D MPLS - 11

12 MPLS history Tag Switching IP on ATM No problems with resolution of addresses Simpler signaling Only one control plan ATM with IP Reusing ATM switching hardware MPLS - 12

13 MPLS history MPλS (Multi-Protocol Lambda Switching) G-MPLS (Generalized MPLS) Packet switching Cell switching Circuit switching (SONET/SDH) Lambda switching Anything switching MPLS - 13 Unifying control plan

14 MPLS key elements MPLS header Contains the label Upgraded routing protocols Constraints in choosing paths Protocols for label distribution Signaling MPLS - 14

15 Shim header MPLS header Level 2 IP packet 20 bit 3 bit 1 8 bit Label Exp S TTL Exp: Experimental bits (CoS) S: Bottom of stack TTL: Time to live MPLS - 15

16 ATM and frame relay Connection oriented layer 2 protocols MPLS labels in layer 2 header VCI/VPI (ATM) DLCI (Frame relay) MPLS - 16

17 Forwarding equivalence class (FEC) Packets that Follow the same path in MPLS network Are treated the same way by each LSR Receive the same label MPLS - 17

18 Label Binding A LSR determines the label it intends to use for packets belonging to a given FEC Downstream binding Packets of the FEC shall be received with chosen label Upstream node to be notified Unsolicited On-demand MPLS - 18

19 Label Mapping The label used by the downstream switch of a link for packets belonging to a FEC is associated to Input label Output port LSP Creation MPLS - 19

20 Label Distribution The downstream switch of a link choses the label to be attached to packets belonging to a FEC when forwarded on the link Downstream Label Binding The label is communicated to the upstream switch Label mapping for the corresponding port MPLS - 20

21 Static label binding (and mapping) Through management Equivalent to PVC ATM Non-scalable No interoperability among managing systems Impossible to have LSPs through different networks MPLS - 21

22 Dynamic label binding Protocol (IP) driven The creation of LSPs is linked to the discovery of routes towards destinations Explicit creation of LSP Explicit signaling Initiated by label edge routers MPLS - 22

23 Label distribution protocols Three alternatives (incompatible) Routing protocol: BGP Only protocol driven Label distribution protocol (LDP) Designed for the purpose Resource reservation protocol (RSVP) Designed for allocation in integrated service networks MPLS - 23

24 Routing protocols Used to determine LSP routing Guide label binding procedures They indirectly determine packet routing MPLS - 24

25 Routing protocols Existing protocols OSPF IS-IS BGP-4 carry topology information In MPLS context they are enhanced d to... MPLS - 25

26 Routing protocols...carry information to constraint routing decisions (constraint data) Capacity of links Link utilization Dependencies among links Used for fault recovery MPLS - 26

27 Enhanced routing protocols Constraint based routing is fundamental to support traffic engineering OSPF TE IS-IS TE MPLS - 27

28 Hop-by-hop routing Each switch decides the next step of LSP path Switches agree on corrispondencies among Ingress and egress labels Labels and FEC Similar to routing for IP packets MPLS - 28

29 Explicit constraint based routing A single switch may choose the path of an LSP For example, LSR ingress Explicit routing The choice is constraint based Constraint based routing MPLS - 29

30 Label distribution protocols CR-LDP Should be modified Constraint-based routing LDP RSVP-TE RSVP for Traffic Engineering To be used with OSPF-TE and IS-IS-TE MPLS - 30

31 New possibilities Traffic engineering Guaranteed quality of service Not yet supported Per-class traffic engineering Synergy with DiffServ Fast fault recovery In less than 50 ms MPLS - 31

32 Control plane and data plane Control plane OSPF IP Continuous updating RIP IS-IS Data plane IGRP BGP Routing database Routing table MPLS - 32

33 Control plane and data plane Signaling (LSP setup) LDP RSVP Routing table Control plane RIP OSPF MPLS IS-IS IGRP BGP LSP setup Data plane Routing database Forwarding table MPLS - 33

34 Traditional IP routing Aggregation! Traffic for D on optimal path D MPLS - 34

35 Traditional IP routing Congestion! Traffic for D on optimal path 4 overloaded links D MPLS - 35

36 Traditional IP routing Underutilization utilization! Traffic for D on optimal path 4 overloaded links 9 underutilized links D MPLS - 36

37 Traffic Engineering Allows traffic distribution D MPLS - 37

38 Traffic Engineering No conge- stion Uniform use D MPLS - 38

39 Can you do it with traditional IP routing? Traffic for D on optimal path 4 overloaded links 9 underutilized links D MPLS - 39

40 It is necessary to choose paths according to load Traffic for D on optimal path overloaded links underutilized links D MPLS - 40

41 In such way, unloaded links are loaded and viceversa... Traffic for D on optimal path overloaded links underutilized links D MPLS - 41

42 ... and routing tables change... Traffic for D on optimal path overloaded links underutilized links D MPLS - 42

43 so does the link load... Traffic for D on optimal path overloaded links underutilized links D MPLS - 43

44 ... and the paths change again!!! Instability! Traffic for D on optimal path overloaded links underutilized links D MPLS - 44

45 Traffic Engineering with MPLS D MPLS - 45

46 Traffic Engineering without MPLS ATM has so far been used for traffic engineering on IP networks Two control plans Routers are ATM-unaware Great number of adjacencies Limitated scalability MPLS - 46

47 Traffic Engineering with MPLS MPLS is IP-aware Only one control plan operating on physical topology Simpler Greater scalability MPLS - 47

48 MPLS extensions MPλS (MPLambdaS) MPLS control plans in optical networks GMPLS (Generalized MPLS) MPLS control plane in any network Packet, circuit, optics, etc MPLS - 48

49 Adding CoS and QoS Resources and service modes may be associated to a FEC at LSP setup Explicit support is required in LSR data plan and control plan MPLS - 49

50 Class of service (CoS) Relative priority among different FECs It does offer absolute guaranties Support of DiffServ model Per-hop behavior EF (expedite forwarding), AF (assured forwarding) Traffic engineering for class DS-aware traffic engineering MPLS - 50

51 Quality of service (QoS) Specific guaranties on Bandwidth Delay Burst size MPLS - 51

52 Advantages of QoS in MPLS Unified network supporting all types of services (marketing message) Support of QoS and real-time services on IP (e.g., voice) is not ready Alot of multi-service networks now have a paradigm Ships-in-the-night ATM protocols are ATM typical services MPLS control plan for IP services MPLS - 52

53 Label Stack hierarchy and scalability Header Layer 2 Label 3 Label 2 Label 1 IP packet MPLS Domain 1 Routing table reduction Forwarding table reduction MPLS Domain 2 MPLS Domain 3 MPLS - 53

54 MPLS and scalability MPLS labels introduce hierarchy Various hierarchical levels, as needed for the necessary scalability Routing tables of transit routers do not have to be comprehensive LSP between edge routers Simpler and faster exact match of labels rather than longest prefix matching MPLS - 54

55 VPN: Virtual Private Network Services similar to those of a private network, but provided on a public infrastructure (IP) Privacy and security Overlapping addressing spaces (private) Non-unique addresses Class of Service (CoS) and Quality of Service (QoS) MPLS - 55

56 VPN based on MPLS MPLS - 56 The labels hide IP addresses of users on the public network MPLS allows a scalable solution for VPN services Other approaches require explicit setting (manual) of tunnels between each pair of websites Number of VPNs Number of VPN members Service flexibility (thanks to FEC)

57 Standardization IETF Internet Engineering Task Force MPLS working group FR/MPLS Alliance Consortium of producers Speed up spreading Aspects omitted by IETF VoMPLS, ADSL MPLS - 57

58 Bibliography T. Tofoni, MPLS Fondamenti e applicazioni alle reti IP, Hoepli, 2003 IETF MPLS Working Group, pls-charter.html E. Rosen, A. Viswanathan, R. Callon, Multiprotocol Label Switching Architecture, RFC 3031, Standards Track, Jan E. Rosen, D. Tappan, G. Fedorkow, Y. Rekhter, D. Farinacci, T. Li, A. Conta, MPLS Label Stack Encoding, RFC 3032, Standards Track, Jan MPLS - 58

59 Bibliography F. Le Faucheur, et al., Multi-Protocol Label Switching (MPLS) Support of Differentiated Services, RFC 3170, Standards Track, May 2002 Davie, B., Lawrence, J., McCloghrie, K., Rekhter, Y., Rosen, E., Swallow, G. and P. Doolan, "MPLS using LDP and ATM VC Switching", RFC 3035, January Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B. Thomas, "LDP Specification", RFC 3036, January MPLS - 59