Multi Protocol Label Switching (an introduction) Karst Koymans. Thursday, March 12, 2015

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1 .. MPLS Multi Protocol Label Switching (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 4.3, 2015/03/09 13:07:57) Thursday, March 12, 2015 Karst Koymans (UvA) MPLS Thursday, March 12, / 26

2 . 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

3 Faster IP forwarding Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

4 Faster IP forwarding IP Forwarding Forwarding IP packets Normally done by destination IP address Routing protocols are used to distribute layer 3 information Decisions are made hop-by-hop independently Connectionless operation Routing protocol should offer consistency Shortcomings Routing tables may become very large Search time is O(log N) for table of size N Limited traffic engineering options Layer 2 and layer 3 information is unrelated Karst Koymans (UvA) MPLS Thursday, March 12, / 26

5 Faster IP forwarding ATM and MPLS Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

6 Faster IP forwarding ATM and MPLS ATM (Asynchronous Transfer Mode) Uses small fixed size cells to transport data Each cell contains 53 bytes A fixed size header of 5 bytes A fixed size payload of 48 bytes Often data needs to be fragmented Uses VCs (Virtual Circuits) between endpoints Switching based on labels An 8-bit (UNI) or 12-bit (NNI) Virtual Path Identifier (VPI) An 16-bit Virtual Channel Identifier (VCI) Switching lookup is now O(1) Promises QoS, for instance low jitter Higher level protocols use the ATM Adaptation Layer (AAL) Karst Koymans (UvA) MPLS Thursday, March 12, / 26

7 Faster IP forwarding ATM and MPLS MPLS (Multi Protocol Label Switching) Defined in RFC 3031 Combine the best of both worlds Packet forwarding Circuit switching Route at the edges, switch at the core Multi Protocol Agnostic to underlying protocols used at layer 2 or 3 Label Switching Uses labels instead of IP addresses Routing at the speed of switching Hybrid, layer 2.5, shim protocol Karst Koymans (UvA) MPLS Thursday, March 12, / 26

8 MPLS Operation Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

9 MPLS Operation MPLS Network MPLS Network Karst Koymans (UvA) MPLS Thursday, March 12, / 26

10 MPLS Operation Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

11 MPLS Operation MPLS Label (RFC 3032) Label Exp S TTL. MPLS packet label fields. Label Exp(erimental) a S(tack) T(ime) T(o) L(ive) Per router local semantics Class of Service Bottom of stack indication Incoming IP TTL. a Renamed to TC (Traffic Class) by RFC 5462 Karst Koymans (UvA) MPLS Thursday, March 12, / 26

12 MPLS Operation LER (Label Edge Router) LSR (Label Switching Router) Label Edge Router Positioned at the edge of the MPLS network Adds or removes labels for incoming and outgoing traffic Also called Edge Label Switch Router (elsr) Label Switch Router Positioned in the core of the MPLS network Swaps labels and forwards packets Does not need to know about IP forwarding Karst Koymans (UvA) MPLS Thursday, March 12, / 26

13 MPLS Operation FEC (Forwarding Equivalence Class) and LSP (Label Switched Path) Forwarding Equivalence Class Packets which are forwarded in the same manner Each label on a link determines a unique FEC Every FEC is associated with a certain LSP Label Switched Path Sequence of intermediate routers on same stack depth on the path from ingress to egress router Hop-by-hop routing Explicit routing Karst Koymans (UvA) MPLS Thursday, March 12, / 26

14 MPLS Operation LIB (Label Information Base) Mapping between previous hop (incoming port, label) and FEC Mapping between FEC and next hop (outgoing port, label) Each router has its own LIB Details are implementation dependent Generates an LFIB (Label Forwarding Information Base) Input Port Incoming Port Label Output Port Outgoing Port Label 1 green 3 blue 2 red 1 orange Karst Koymans (UvA) MPLS Thursday, March 12, / 26

15 MPLS Operation MPLS Operation (continued).0 Receive IP packet at edge router MPLS Network Classify into FEC green.2 Push (label green).3 Swap (label green, label red).4 Swap (label red, label blue).5 Pop (label blue).6 Forward IP packet to destination Karst Koymans (UvA) MPLS Thursday, March 12, / 26

16 MPLS Operation MPLS Control and Label Management Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

17 MPLS Operation MPLS Control and Label Management MPLS Separation of Control and Data Control Plane Exchange layer 3 and label information Several label distribution protocols (LDP, CR-LDP, RSVP-TE) Also piggybacked on routing protocols (OSPF-TE, ISIS-TE, MP-BGP) Data Plane Switch (forward) packets based on labels Push (ingress) Swap (intermediate) Swap and push (start LSP tunnel) Pop and swap (end LSP tunnel) Pop (egress) Karst Koymans (UvA) MPLS Thursday, March 12, / 26

18 MPLS Operation MPLS Control and Label Management LDP (Label Distribution Protocol) UDP discovery and TCP session with peers Adjacent LSRs inform each other of the label bindings Downstream LSR determines the label On demand or unsolicited An IGP protocol is configured on all LSRs New IGP routes lead to new label bindings Labels can be withdrawn when IGP routes are no longer valid Hard-state Expected to work until explicitly torn down Karst Koymans (UvA) MPLS Thursday, March 12, / 26

19 MPLS Operation MPLS Control and Label Management RSVP-TE (Resource Reservation Protocol Traffic Engineering) Extension of RSVP Unreliable delivery (protocol 46; sometimes UDP) Soft-state Information needs to be periodically refreshed An LSP is created by propagating an RSVP message to the endpoint Paths are terminated if not refreshed on time Karst Koymans (UvA) MPLS Thursday, March 12, / 26

20 MPLS Applications Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

21 MPLS Applications Applications (1) TE (Traffic Engineering) Traffic steering across network in order to fully utilize resources With the help of RSVP-TE and OSPF-TE or IS-IS-TE Full network view (OSPF, IS-IS) and extra information about link state RSPV-TE creates LSPs on demand QoS (Quality of Service) Different types of service across the network Enforcing drop probability, bandwidth and delay (queueing) CoS bits or FEC (destination + class of service) Karst Koymans (UvA) MPLS Thursday, March 12, / 26

22 MPLS Applications Applications (2) VPN (Virtual Private Network) Private connections over shared networks Layer 2 or layer 3 based Business can choose the needed type of service Stacked labels: egress router and VPN identity LDP (layer 2) or BGP (layer 3) is used to transport label information Karst Koymans (UvA) MPLS Thursday, March 12, / 26

23 MPLS Applications MPLS VPN techniques Outline. 1 Faster IP forwarding ATM and MPLS. 2 MPLS Operation MPLS Control and Label Management. 3 MPLS Applications MPLS VPN techniques Karst Koymans (UvA) MPLS Thursday, March 12, / 26

24 MPLS Applications MPLS VPN techniques Layer 2 VPN (1) AToM (Any Transport over MPLS) Transports layer 2 frames over an MPLS Network ATM, Frame-Relay, PPP, Ethernet Point-to-point service From ingress router/interface to egress router/interface Identified by using an inner label Karst Koymans (UvA) MPLS Thursday, March 12, / 26

25 MPLS Applications MPLS VPN techniques Layer 2 VPN (2) VPLS (Virtual Private LAN Service) Transports layer 2 frames over an MPLS Network Works multipoint-to-multipoint The IP/MPLS core operates as a big virtual switch Outer label used for normal MPLS forwarding Inner label used for VPLS instances Karst Koymans (UvA) MPLS Thursday, March 12, / 26

26 MPLS Applications MPLS VPN techniques Layer 3 VPN Uses the MP-BGP (Multi Protocol BGP) extension of BGP Introduces the VPN-IPv4 address family Extends the 32-bit IPv4 address with a 64-bit RD (route distinguisher) A BGP route for VPN-IPv4 includes an MPLS label Each VPN has its own VRF (VPN Routing and Forwarding) instance Keeping separate routing tables for the VPNs Also separate from the global routing table MPLS forwarding uses stacked labels Outer label for LSP forwarding Inner label to differentiate between different VPNs Karst Koymans (UvA) MPLS Thursday, March 12, / 26