mpls

MultiProtocol Label Switching (MPLS) Agenda • • • • MPLS - The Motivation How MPLS Works ! MPLS Technology MPLS Application July 29, 2000 TECON 2000 2 MPLS - The Motivation • IP Protocol Suite - the most predominant networking technology. • Voice & Data convergence on a single network infrastructure. • Continual increase in number of users. • Demand for higher connection speeds. • Increase in traffic volumes. July 29, 2000 TECON 2000 3 MPLS Working Groups and Standards • Standardized by the IETF - currently in Draft stage. • MPLS recommendations are done by IP players for IP services • MPLS core components are generic • MPLS doesn’t use specific technology process (e.g. ATM/FR signaling protocol PNNI or ATM OAM flow) MPLS and ISO model IETF main goal is that when a layer is added, no modification is needed on the existing layers. All new protocol must be backward compatible Applications 7 to 5 TCP IP MPLS Frame FR Relay UDP 4 3 PPP PPP ATM (*) ATM (*) 2 Physical (Optical - Electrical) 1 (*) ATM overlay model (without addressing and P-NNI) is considered as an ISO layer 2 protocol. July 29, 2000 TECON 2000 5 MPLS • is a data-carrying mechanism that belongs to the family of packet-switched networks. • is generally considered to lie between traditional definitions of Layer 2 (data link layer) and Layer 3 (network layer), and thus is often referred to as a "Layer 2.5" protocol. July 29, 2000 TECON 2000 6 Agenda • • • • Motivation for MPLS How MPLS Works ! MPLS Technology MPLS Application July 29, 2000 TECON 2000 7 MPLS Architecture LSP Routing protocol FEC table Attributes Classification Label assignment Label swapping Label removal OSPF OSPF OSPF Local table Local table Local table Precedence Label table Label Switch Local table Local table Local table Layer 2 Layer 2 Layer 2 Layer 1 Ingress Node Layer 1 Core Node Layer 1 Egress Node July 29, 2000 TECON 2000 8 MPLS process Label Switch Path OSPF / RIP / IS-IS Label removal FEC FEC FEC Label swapping Classification Label assignment Precedence Label table Label table Label table Layer 2 Layer 2 Layer 2 Layer 1 Ingress Node Layer 1 Core Node Layer 1 Egress Node July 29, 2000 TECON 2000 9 MPLS Cloud LER L3 Routing LER LER L3 Routing LER L3 Routing IP Packet IP Packet w/ Label July 29, 2000 TECON 2000 L3 Routing LSR Label Swapping LSR Label Swapping LER L3 Routing 10 MPLS Link Layers & Label Encapsulation Layer2 ATM VPI VCI FR DLCI Ethernet PPP “Shim Label” “Shim header” ……. IP | PAYLOAD July 29, 2000 TECON 2000 11 Agenda • • • • Motivation for MPLS How MPLS Works ! MPLS Technology MPLS Application July 29, 2000 TECON 2000 12 Some MPLS Terms... • • • • • • • • • LER - Label Edge Router LSR - Label Switch Router FEC - Forward Equivalence Class Label - Associates a packet to a FEC Label Stack - Multiple labels containing information on how a packet is forwarded. Shim - Header containing a Label Stack Label Switch Path - path that a packet follows for a specific FEC LDP - Label Distribution Protocol, used to distribute Label information between MPLS-aware network devices Label Swapping - manipulation of labels to forward packets towards the destination. July 29, 2000 TECON 2000 13 FEC Classification •A packet can be mapped to a particular FEC based on the following criteria: •destination IP address, •source IP address, •TCP/UDP port, •in case of inter AS-MPLS, Source-AS and Dest-AS, •class of service, •application used, •… •any combination of the previous criteria. Ingress Label 6 FEC 138.120.6/24 - xxxx Egress Label 9 •FECs are manually initiated by the operator •A FEC is associated at least one Label Ingress Label Ingress Label FEC FEC Attribute Egress Label Attribute Egress Label 6 6 July 29, 2000 TECON 2000 138.120.6/24 - xxxx 138.120.6/24 - xxxx A B 9 12 14 What is a Label ? • A short, fixed length, locally significant identifier used to identify a FEC. • The label can be identified by the L2 technology identifier (e.g. VPI/VCI for ATM, DLCI for FR or MPLS label for PPP/Ethernet). L2 Type Port Ingress Label FEC L2 Type ATM Egress Label Port ATM ATM Gig Eth 1-1 1-1 5-1 12 (i.e. 4/65) 15 (i.e. 0/25) 7 F1 F4 F1 22 (i.e. 5/65)3-4 9 (i.e. 101) 5-1 22 (i.e. 4/65)3-4 FR ATM July 29, 2000 TECON 2000 15 MPLS Label Assignment Schemes • Topology Driven – Label assignment in response to routing protocols (OSPF and BGP) updates • Control Driven – Label assignment in response to RSVP, CRLDP requests • Traffic Driven – Label assignment in response to flow detection & triggering July 29, 2000 TECON 2000 16 The MPLS Shim Header • The Label (Shim Header) is represented as a sequence of Label Stack Entry • Each Label Stack Entry is coded by 4 bytes (32 bits) as described • 20 Bits is reserved for the Label Identifier (also named Label) Label (20 bits) Label : Exp : S: TTL : July 29, 2000 TECON 2000 Exp (3 bits) S (1 bit) TTL (8bits) Label value (0 to 15 are reserved for special use) Experimental Use Bottom of Stack (set to 1 for the last entry in the label) Time To Live 17 Label Switched Path Ingress Ingress Interface Label FEC Egress Egress Interface Label 138.120 3 12 Ingress Ingress Interface Label 1 FEC Egress Egress Interface Label 138.120 12 4 x 1 5 MPLS switch 1 3 4 1 2 3 1 2 2 3 138.120 127.20 MPLS switch 1 3 2 MPLS switch 192.168 MPLS switch Ingress Ingress Interface Label 1 x FEC Egress Egress Interface Label 5 3 138.120 18 July 29, 2000 TECON 2000 Hop by Hop IP forwarding Ingress Ingress Interface Label 1 Default FEC Egress Egress Interface Label None 3 Default Ingress Ingress Interface Label FEC Egress Egress Interface Label 1 Default None 4 x ?? 1 MPLS switch 3 ?? 1 2 2 4 3 138.120 138.120.6.12 127.20 MPLS switch 1 3 2 1 2 3 MPLS switch 192.168 138.120.6.12 ?? Ingress Ingress Interface Label 1 x MPLS switch FEC Egress Egress Interface Label None 3 Default 19 July 29, 2000 TECON 2000 MPLS Label Distribution Protocol • LDP - a set of procedures by which one LSR informs the other of the FEC-to-Label binding it has made. • Currently, several protocols used as Label Distribution Protocol (LDP) are available: – RSVP-TE (MPLS extension) – LDP and CR-LDP – BGP-4 MPLS extensions • Label Distribution schemes July 29, 2000 TECON 2000 20 Downstream stream on demand Ingress Ingress Interface Label 1 5 FEC Egress Egress Interface Label 138.120 3 12 Ingress Ingress Interface Label 1 FEC Egress Egress Interface Label 12 138.120 4 x MPLS switch 1 3 4 1 2 3 1 2 2 138.120 127.20 MPLS switch 1 3 2 3 MPLS switch 192.168 MPLS switch Ingress Ingress Interface Label 1 x FEC Egress Egress Interface Label 138.120 3 5 The label is requested by the upstream node and the downstream node defines the label used. 21 July 29, 2000 TECON 2000 Edge LSR Features – – – – – – Routing protocols FEC Classification Initiates LSP setup for Downstream On Demand method Adaptation of non-MPLS data to MPLS data Layer 2 translation for MPLS data At least one LDP protocol – Edge LSR is counted into the TTL count as a regular router July 29, 2000 TECON 2000 22 Core LSR Features – Routing protocols – Propagates Downstream On Demand method (request and mapping) – Layer 2 translation – High speed label forwarding/switching – At least one LDP protocol July 29, 2000 TECON 2000 23 SWAP PUSH POP • In a swap operation the label is swapped with a new label, and the packet is forwarded along the path associated with the new label. • In a push operation a new label is pushed on top of the existing label, effectively "encapsulating" the packet in another layer of MPLS. This allows hierarchical routing of MPLS packets. • In a pop operation the label is removed from the packet, which may reveal an inner label below. This process is called "decapsulation". If the popped label was the last on the label stack, the packet "leaves" the MPLS tunnel. This is usually done by the egress router, but see PHP below. July 29, 2000 TECON 2000 24 Agenda • • • • Motivation for MPLS How MPLS Works ! MPLS Technology MPLS Application July 29, 2000 TECON 2000 25 MPLS Advantages • • • • • Simplified Forwarding Efficient Explicit Routing Traffic Engineering QoS Routing Mappings from IP Packet to Forwarding Equivalence Class (FEC) • Partitioning of Functionality • Common Operation over Packet and Cell media July 29, 2000 TECON 2000 26 MPLS - the Future • Who will use MPLS? – Large-scale data networks used by Enterprises, Carriers and ISPs. • Why MPLS? – Delivers high speed L2 (really “Label”) switching at low cost vs. traditional L3 routing – Provides Traffic Engineering - allows the user to direct traffic based on network utilization and demand. – Ease of provisioning QoS – Support for VPNs July 29, 2000 TECON 2000 27 MPLS VPN : MPLS topology VPN 2 138.120.6.0/24 LSR 138.120.8.0/24 Site B VPN 1 Site A ISP Backbone LSR LSP 47 LSR LSR LSR LSP 32 LSR Site A 138.120.8.0/24 Site B 138.120.6.0/24 VPN 2 July 29, 2000 TECON 2000 VPN 1 28 MPLS - Some Major Vendors • • • • • Alcatel Cisco Juniper Networks Nortel Lucent July 29, 2000 TECON 2000 29