MPLS Tutorial Bilel N. Jamoussi, Ph.D. Senior Network Architect Carrier Data Networks

MPLS Tutorial Bilel N. Jamoussi, Ph.D. Senior Network Architect Carrier Data Networks jamoussi@nortelnetworks.com

MPLS Tutorial 1 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Copyright notice: —Copyright © 1999 by Nortel Networks. All rights reserved. Except as permitted under the United States Copyright Act of 1976, no part of this document may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of Nortel Networks. Proprietary notice: —This document contains trade secrets of Nortel Networks. It is provided to persons and organizations doing business with Nortel Networks solely for their use in conducting that business. Disclosure of the contents of this document in whole or in part to any other parties without the prior written consent of Nortel Networks is expressly prohibited. Brand names and/or trademarks: —Brand names or products cited in this document may be trade names or trademarks. Where there may be proprietary claims to such trademarks or trade names, the name has been used with an initial capital. Regardless of the capitalization used, all such use has been in an editorial fashion without any intent to convey endorsement whatsoever of the product or trademark claimant. Nortel Networks expresses no judgment as to the validity or legal status of any such proprietary claims. Engineering Services Disclaimer: —Information contained in this document is believed to be accurate. However, Nortel Networks does not guarantee the completeness or accuracy of any of the published information. This work is published with the understanding that Nortel Networks is supplying information, but not attempting to render engineering or other professional services. If such services are required, the assistance of the appropriate professional should be sought.

MPLS Tutorial 2 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Tutorial Outline Overview Label Encapsulations Label Distribution Protocols MPLS and ATM IETF Status Nortel Networks Activity Summary

MPLS Tutorial 3 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS Motivations Flexibility (L2/L3 Integration) —Media Support: ATM, FR, Ethernet, PPP —Operate IP over Multiservice ATM —More than destination-based Forwarding IP Traffic Engineering —Constraint-based Routing IP-VPN —Tunneling mechanism VOIP —Connection-oriented Paths and QoS

MPLS Tutorial 4 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 47.1 47.2 47.3 1 2 3 1 2 3 1 2 3 All Nodes Run Standard IP Routing

MPLS Tutorial 5 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 47.1 47.2 47.3 IP 47.1.1.1 1 2 3 1 2 1 2 3 IP Destination Lookup at Each Hop

MPLS Tutorial 6 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Layer 3 Routing Layer 2 Forwarding Label Switch Router MPLS involves routing at the edges, switching in the core IP PacketLabel IP Packet Label Switch Router Edge Label Switch Router (LSR) IP PacketLabelIP PacketLabel IP Packet Edge Label Switch Router (LSR) Multiprotocol Label Switching (MPLS)

MPLS Tutorial 7 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LDP: Label Distribution Protocol FEC: Forwarding Equivalence Class LSP: Label Switched Path LSR: Label Switching Router LER: Label Edge Router (Note that LER is a Nortel Networks term describing the edge LSR function) MPLS Terminology

MPLS Tutorial 8 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA FEC = “A subset of packets that are all treated the same way by a router” The concept of FECs provides for a great deal of flexibility and scalability In conventional routing, a packet is assigned to an FEC at each hop (i.e., L3 lookup); in MPLS, it is only done once at the network ingress Packets are destined for different address prefixes, but can be mapped to common egress router, treated as equivalent FEC Packets are destined for different address prefixes, but can be mapped to common egress router, treated as equivalent FEC LSR LSP FEC Forwarding Equivalence Classes

MPLS Tutorial 9 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Label Switched Path (LSP) Set Up Across Network Incoming Packets Classified, Labeled Interior Nodes Forwarded Along LSP Based on Labels Egress Node Removes Label Before Forwarding Two types of Label Switched Paths: Hop-by-hop Explicit Routing Label Switched Path — Concept

MPLS Tutorial 10 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 47.1 47.2 47.3 1 2 3 1 2 1 2 3 3 Mapping: 0.40 Request: 47.1 Mapping: 0.50 Request: 47.1 MPLS Label Distribution

MPLS Tutorial 11 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 47.1 47.2 47.3 1 2 3 1 2 1 2 3 3 IP 47.1.1.1 Label Switched Path (LSP)

MPLS Tutorial 12 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Explicit Routing LSR B LSR C LSR D LSR E LSR A Forward to LSR B LSR C LSR D LSR E Forward to LSR B LSR C LSR D LSR E Ingress node (or egress node) determines path from ingress to egress Operator has routing flexibility (policy-based, QoS-based) Required for MPLS traffic engineering Two signaling options proposed in the standards: RSVP, CR-LDP LSPs: Explicit Routing

MPLS Tutorial 13 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 47.1 47.2 47.3 1 2 3 1 2 1 2 3 3 IP 47.1.1.1 Traffic Engineered Path

MPLS Tutorial 14 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Tutorial Outline Overview Label Encapsulations Label Distribution Protocols MPLS & ATM IETF Status Nortel Networks Activity Summary

MPLS Tutorial 15 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS ATMFREthernetPPP MPLS Encapsulation is specified over various media types VPIVCIDLCI“Shim” L2 Label Label Encapsulation

MPLS Tutorial 16 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS is intended to run over multiple link layers Specifications for the following link layers currently exist: ATM: label contained in VCI/VPI field of ATM header Frame Relay: label contained in DLCI field in FR header PPP/LAN: uses ‘shim’ header inserted between L2 and L3 headers Fields and functionality may vary between different link layers — ATM/FR have to adapt to existing structure — PPP/LAN header has more freedom to incorporate useful features (CoS, TTL) Translation between link-layers types must be supported MPLS intended to be “multiprotocol” below as well as above MPLS Link Layers

MPLS Tutorial 17 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA ATM LSR constrained by the cell format imposed by existing ATM standards VPIPT CLP HEC 5 Octets ATM Header Format VCI AAL5 Trailer Network Layer Header and Packet (e.g., IP) 1 n AAL 5 PDU Frame (nx48 bytes) Generic Label Encap. (PPP/LAN format) ATM SAR ATM Header ATM Payload Top one or two labels are contained in the VPI/VCI fields of ATM header — one in each or single label in combined field, negotiated by LDP Further fields in stack are encoded with ‘shim’ header in PPP/LAN format — must be at least one, with bottom label distinguished with ‘explicit NULL’ TTL is carried in top label in stack, as a proxy for ATM header (that lacks TTL) 48 Bytes Label Option 1 Option 2 Combined Label Option 3LabelATM VPI (Tunnel) MPLS Encapsulation — ATM

MPLS Tutorial 18 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA n 1 DLCI C/ R EAEA DLCI FE CN BE CN DEDE EAEA Q.922 Header Generic Encap. (PPP/LAN Format) Layer 3 Header and Packet DLCI Size = 10, 17, 23 Bytes Current label value carried in DLCI field of Frame Relay header Can use either 2 or 4 octet Q.922 address (10, 17, 23 bytes) Generic encapsulation contains n labels for stack of depth n — top label contains TTL (which FR header lacks), ‘explicit NULL’ label value MPLS Encapsulation — Frame Relay

MPLS Tutorial 19 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LabelExp. S TTL Label: Label Value, 20 bits (0-16 reserved) Exp.: Experimental, 3 bits (was Class of Service) S:Bottom of Stack, 1 bit (1 = last entry in label stack) TTL:Time to Live, 8 bits Layer 2 Header (e.g., PPP, 802.3) Network Layer Header and Packet (e.g., IP) 4 Octets MPLS ‘Shim’ Headers (1-n) 1 n Network layer must be inferable from value of bottom label of the stack TTL must be set to the value of the IP TTL field when packet is first labeled When last label is popped off stack, MPLS TTL to be copied to IP TTL field Pushing multiple labels may cause length of frame to exceed layer-2 MTU — LSR must support “Max. IP Datagram Size for Labeling” parameter — any unlabeled datagram greater in size than this parameter is to be fragmented MPLS on PPP links and LANs uses ‘Shim’ Header Inserted Between Layer 2 and Layer 3 Headers MPLS on PPP links and LANs uses ‘Shim’ Header Inserted Between Layer 2 and Layer 3 Headers Label Stack Entry Format MPLS Encapsulation — PPP & LAN Data Links

MPLS Tutorial 21 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Label Distribution Protocols Overview of Hop-by-hop and Explicit Label Distribution Protocol (LDP) Constraint-based Routing LDP (CR-LDP) Extensions to RSVP Extensions to BGP

MPLS Tutorial 22 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS will form label switched paths by one of two methods — hop-by-hop routing or explicit routing MPLS will form label switched paths by one of two methods — hop-by-hop routing or explicit routing Hop-by-Hop Routing LSR B LSR C LSR D LSR E LSR A Forward to LSR B Forward to LSR B Forward to LSR C Forward to LSR C Forward to LSR D Forward to LSR D Forward to LSR E Forward to LSR E Forward to LSR... Forward to LSR... Explicit Routing LSR B LSR C LSR D LSR E LSR A Forward to LSR B LSR C LSR D LSR E Forward to LSR B LSR C LSR D LSR E Each node runs layer 3 routing protocol Routing decisions made independently at each node Also known as ‘source routing’ or ‘traffic steering’ Ingress node (or egress node) determines path from ingress to egress LSPs: Hop-by-Hop vs. Explicit Routing

MPLS Tutorial 23 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Hop-by-Hop Routing Explicit Routing Centralized topology awareness (in ingress node) Path setup/tear-down/refresh required Requires manual provisioning or creation of new routing protocol Backup paths may be preprovisioned for rapid restoration Operator has routing flexibility (policy-based, QoS-based) Easily used for traffic engineering Distributes topology awareness No path setup/tear-down/refresh required Automates routing using industry standard protocols (e.g., OSPF, ISIS) Loop detection/prevention required Reroute on failure impacted by convergence time of routing protocol Existing routing protocols are destination prefix-based Difficult to perform traffic engineering, QoS-based routing Explicit routing shows great promise for traffic engineering, at the cost of operator involvement (or new routing protocols) Explicit routing shows great promise for traffic engineering, at the cost of operator involvement (or new routing protocols) Comparison — Hop-by-Hop vs. Explicit Routing

MPLS Tutorial 24 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR B LSR C LSR D LSR E LSR A Forward to LSR B LSR C LSR D LSR E Forward to LSR B LSR C LSR D LSR E Connectionless nature of IP implies that routing is based on information in each packet header Source routing is possible, but path must be contained in each IP header — lengthy paths increase size of IP header, make it variable size, increase overhead — some gigabit routers require ‘slow path’ option-based routing of IP packets Source routing has not been widely adopted in IP and is seen as impractical — some network operators may filter source-routed packets for security reasons MPLS enables the use of source routing by its connection-oriented capabilities — paths can be explicitly set up through the network — the ‘label’ now can represent the explicitly routed path Loose and strict source routing can be supported MPLS makes the use of source routing in the Internet practical Explicit Routing — MPLS vs. Traditional Routing

MPLS Tutorial 25 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Label distribution ensures that adjacent routers have a common view of FEC label bindings Routing Table: Addr-prefix Next Hop 47.0.0.0/8 LSR2 Routing Table: Addr-prefix Next Hop 47.0.0.0/8 LSR2 LSR1 LSR2 LSR3 IP Packet 47.80.55.3 Routing Table: Addr-prefix Next Hop 47.0.0.0/8 LSR3 Routing Table: Addr-prefix Next Hop 47.0.0.0/8 LSR3 For 47.0.0.0/8 use label ‘17’ Label Information Base: Label-In FEC Label-Out 17 47.0.0.0/8 XX Label Information Base: Label-In FEC Label-Out 17 47.0.0.0/8 XX Label Information Base: Label-In FEC Label-Out XX 47.0.0.0/8 17 Label Information Base: Label-In FEC Label-Out XX 47.0.0.0/8 17 Step 1: LSR creates binding between FEC and label value Step 2: LSR communicates binding to adjacent LSR Step 3: LSR inserts label value into forwarding base Common understanding of which FEC the label is referring to! Label distribution can either piggyback on top of an existing routing protocol, or a dedicated label distribution protocol (LDP) can be created Label distribution can either piggyback on top of an existing routing protocol, or a dedicated label distribution protocol (LDP) can be created Label Distribution Protocol (LDP) — Purpose

MPLS Tutorial 26 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR1 LSR2 Label Distribution can take place using one of two possible methods Downstream Label Distribution Label-FEC Binding LSR2 and LSR1 are said to have an “LDP adjacency” (LSR2 being the downstream LSR) LSR2 discovers a ‘next hop’ for a particular FEC LSR2 generates a label for the FEC and communicates the binding to LSR1 LSR1 inserts the binding into its forwarding tables If LSR2 is the next hop for the FEC, LSR1 can use that label knowing that its meaning is understood LSR1 LSR2 Downstream-on-Demand Label Distribution Label-FEC Binding LSR1 recognizes LSR2 as its next-hop for an FEC A request is made to LSR2 for a binding between the FEC and a label If LSR2 recognizes the FEC and has a next hop for it, it creates a binding and replies to LSR1 Both LSRs then have a common understanding Request for Binding Both methods are supported, even in the same network at the same time. For any single adjacency, LDP negotiation must agree on a common method. Label Distribution — Methods

MPLS Tutorial 27 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Independent LSP Control Ordered LSP Control Next Hop (for FEC) Outgoing Label Incoming Label MPLS path forms as associations are made between FEC next-hops and incoming and outgoing labels Each LSR makes independent decision on when to generate labels and communicate them to upstream peers Communicate label-FEC binding to peers once next-hop has been recognized LSP is formed as incoming and outgoing labels are spliced together Label-FEC binding is communicated to peers if: - LSR is the ‘egress’ LSR to particular FEC - Label binding has been received from upstream LSR LSP formation ‘flows’ from egress to ingress Definition Example Cisco’s Tag Switching IBM’s ARIS Comparison Labels can be exchanged with less delay Does not depend on availability of egress node Granularity may not be consistent across the nodes at the start May require separate loop detection/mitigation method Requires more delay before packets can be forwarded along the LSP Depends on availability of egress node Mechanism for consistent granularity and freedom from loops Used for explicit routing and multicast Both methods are supported in the standard and can be fully interoperable Distribution Control: Ordered vs. Independent

MPLS Tutorial 28 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR1 LSR2 LSR3 LSR4 LSR5 Binding for LSR5 Binding for LSR5 Binding for LSR5 An LSR may receive label bindings from multiple LSRs Some bindings may come from LSRs that are not the valid next-hop for that FEC Liberal Label Retention Conservative Label Retention LSR1 LSR2 LSR3 LSR4 Label Bindings for LSR5 Valid Next Hop LSR4’s Label LSR3’s Label LSR2’s Label LSR1 LSR2 LSR3 LSR4 Label Bindings for LSR5 Valid Next Hop LSR4’s Label LSR3’s Label LSR2’s Label LSR maintains bindings received from LSRs other than the valid next-hop If the next-hop changes, it may begin using these bindings immediately May allow more rapid adaptation to routing changes Requires an LSR to maintain many more labels LSR only maintains bindings received from valid next-hop If the next-hop changes, binding must be requested from new next-hop Restricts adaptation to changes in routing Fewer labels must be maintained by LSR Label-Retention method trades-off between label capacity and speed of adaptation to routing changes Label Retention Methods

MPLS Tutorial 29 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Hop-by-Hop Routing LSR B LSR C LSR D LSR E LSR A Forward to LSR B Forward to LSR B Forward to LSR C Forward to LSR C Forward to LSR D Forward to LSR D Forward to LSR E Forward to LSR E Forward to LSR... Forward to LSR... Each node runs layer 3 routing protocol Routing decisions made independently at each node Distributes topology awareness Automates routing using industry standard protocols (e.g., OSPF, ISIS) Difficult to perform traffic engineering LSPs: Hop-by-Hop

MPLS Tutorial 30 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Outline CR-LDP Solution overview CR-LDP update CR-LDP QoS Summary

MPLS Tutorial 31 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR BLSR CLER DLER A 1. Label Request message. It contains ER path. ER Label Switched Path 2. Request message processed and next node determined. Path list modified to. 3. Request message terminates. IngressEgress 4. Label mapping message originates. 5. LSR C receives label to use for sending data to LER D. Label table updated. 6. When LER A receives label mapping, the ER established. Simple — part of the MPLS LDP protocol Robust — signaling built upon reliable TCP layer Scalable — no need to refresh LSP state Interoperable — proven multivendor interoperability ER-LSP Setup using CR-LDP

MPLS Tutorial 32 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS Traffic Engineering Traffic Engineering requires a solution to route LSPs according to various constraints Solution has to be: —Scalable —Reliable CRLDP use LDP messages to signal these various constraints

MPLS Tutorial 33 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Constraint-based LSP Setup using LDP Uses LDP Messages & TLVs —LDP runs on a reliable transport (TCP) Does NOT require hop-by-hop —DOD-O can be used for loose segments Introduces additional TLVs to the base LDP specification to signal ER, and other “constraints” TLVs for error handling & diagnostics

MPLS Tutorial 34 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Why CR-LDP? Runs on TCP Reliable Hard StateScalable QoS Support ATM-like, FR-like, & Diffserv —More apt to integrate/migrate in existing FR and ATM networks and to support emerging diffserev-based POS gigabit routers Demonstrated interoperability Simple protocol based on LDP, output of MPLS WG

MPLS Tutorial 35 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Latest CRLDP Revision Constraint-based routing overview section CR-TLV is broken in separate TLVs —Explicit route, route pinning, pre-emption ER-Hop TLV encoding consistent with LDP —2-byte type, 2-byte length, variable length content Traffic TLVs and QoS

MPLS Tutorial 36 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA CR-LDP TLVs CR-LSP FEC Element —An opaque FEC element type 0x04 value (0 octet) LSPID TLV —A CRLSP unique identifier within an MPLS network. ER-Hop Type (4) LSPID TLV —The LSPID is used to identify the tunnel ingress point as the next hop in the ER. Resource Class (Color) TLV —32 bit mask indicating which of the 32 "administrative groups" or "colors" of links the CRLSP can traverse.

MPLS Tutorial 37 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA CR-LDP Label Request Message

MPLS Tutorial 38 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Unlabeled IP CRLDP MPLS domain HBH only MPLS domain Loosely routed segment CRLDP Traffic and QoS In the crldp-00 draft three service classes (delay sensitive, throughput sensitive and best effort) were defined. This is inflexible and it's hard to map existing and new applications onto these service definitions. In crldp-01 only CRLSP traffic and QoS parameters of a CRLSP are defined. These describe the characteristics of the CRLSP.

MPLS Tutorial 39 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Traffic Parameters TLV

MPLS Tutorial 40 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA CRLSP characteristics not edge functions The approach is like diffserv’s separation of PHB from edge The parameters describe the “path behavior” of the CRLSP, i.e., the CRLSP’s characteristics Dropping behavior is not signaled —Dropping may be controlled by DS packet markings CRLSP characteristics may be combined with edge functions (which are undefined in CRLDP) to create services —Edge functions can perform packet marking —Example services are in an appendix

MPLS Tutorial 41 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Peak Rate The maximum rate at which traffic should be sent to the CRLSP Defined by a token bucket with parameters —Peak data rate (PDR) —Peak burst size (PBS) Useful for resource allocation If a network uses the peak rate for resource allocation then its edge function should regulate the peak rate May be unused by setting PDR or PBS or both to positive infinity

MPLS Tutorial 42 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Committed Rate The rate that the MPLS domain commits to be available to the CRLSP Defined by a token bucket with parameters —Committed data rate (CDR) —Committed burst size (CBS) Committed rate is the bandwidth that should be reserved for the CRLSP CDR = 0 makes sense; CDR = +  less so CBS describes the burstiness with which traffic may be sent to the CRLSP

MPLS Tutorial 43 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Excess Burst Size Measure the extent by which the traffic sent on a CRLSP exceeds the committed rate Defined as an additional limit on the committed rate’s token bucket Can be useful for resource reservation If a network uses the excess burst size for resource allocation then its edge function should regulate the parameter and perhaps mark or drop packets EBS = 0 and EBS = +  both make sense

MPLS Tutorial 44 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Frequency Specifies how frequently the committed rate should be given to CRLSP Defined in terms of “granularity” of allocation of rate Constrains the variable delay that the network may introduce Constrains the amount of buffering that an LSR may use Values: —Very frequently: no more than one packet may be buffered —Frequently: only a few packets may be buffered —Unspecified: any amount of buffering is acceptable

MPLS Tutorial 45 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Weight Specifies the CRLSP’s weight in the “relative share algorithm” Implied but not stated: —CRLSPs with a larger weight get a bigger relative share of the “excess bandwidth” Values: —0 — the weight is not specified —1-255 — weights; larger numbers are larger weights The definition of “relative share” is network specific

MPLS Tutorial 46 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Negotiation Flags

MPLS Tutorial 47 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR BLSR CLER DLER A 1. Path message. It contains ER path. 2. New path state. Path message sent to next node. Per-hop Path and Resv refresh unless suppressed. 3. Resv message originates. Contain the label to use and the required traffic/QoS para. 4. New reservation state. Resv message propagated upstream. 5. When LER A receives Resv, the ER established. 6. ResvConf message (o). More complex — signaling in addition to MPLS LDP protocol Unreliable — signaling built upon UDP Scalability concerns — Significant number of refresh messages to process Interoperability concerns — IETF draft underspecified, no proven interoperability ER-LSP Setup Using RSVP

MPLS Tutorial 48 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA BGP Extensions A mechanism to exchange label binding information among BGP peers by adding (piggybacking) the label mapping information on the BGP route update

MPLS Tutorial 50 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS & ATM Various Modes of Operation —Label-controlled ATM —Tunneling through ATM —Ships in the night with ATM ATM Merge —VC merge —VP merge

MPLS Tutorial 51 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Several models for running MPLS on ATM: 1. Label-Controlled ATM: Use ATM hardware for label switching Replace ATM Forum SW by IP/MPLS IP Routing MPLS ATM HW MPLS & ATM

MPLS Tutorial 52 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Label switching is used to forward network-layer packets It combines the fast, simple forwarding technique of ATM with network layer routing and control of the TCP/IP protocol suite IP Packet 17 IP Packet 05 B A D C Forwarding Table B 17 C 05 Port Label Switching Router Forwarding Table Network Layer Routing (e.g., OSPF, BGP4) Label Packets forwarded by swapping short, fixed-length labels (i.e., ATM technique) Packets forwarded by swapping short, fixed-length labels (i.e., ATM technique) Switched path topology formed using network layer routing (i.e., TCP/IP technique) Switched path topology formed using network layer routing (i.e., TCP/IP technique) Label ATM Label Switching is the combination of L3 routing and L2 ATM switching Label-Controlled ATM

MPLS Tutorial 53 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS ATM Network MPLS LSRLSR LSRLSR VCVP Two Models Internet Draft: áVCID notification over ATM Link 2. MPLS Over ATM

MPLS Tutorial 54 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA ATM SW LSRLSR ATMMPLS ATM SW LSRLSR 3. Ships in the Night ATM Forum and MPLS control planes both run on the same hardware but are isolated from each other, i.e., they do not interact. This allows a single device to simultaneously operate as both an MPLS LSR and an ATM switch. Important for migrating MPLS into an ATM network.

MPLS Tutorial 55 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Ships in the Night Requirements Resource Management —VPI.VCI Space Partitioning —Traffic management –Bandwidth Reservation –Admission Control –Queuing & Scheduling –Shaping/Policing —Processing Capacity

MPLS Tutorial 56 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Bandwidth Guarantees Flexibility A.Full Sharing A. Full Sharing Port Capacity Pool 1 MPLSMPLS ATMATMMPLSATM Available B. Protocol Partition Pool 2 50%50% rt-VBRrt-VBR Pool 1 50%50% ATMATM MPLS ATM Available Available C. Service Partition Pool 2 50%50% nrt-VBRnrt-VBR COS1COS1 Pool 1 50%50% rt-VBRrt-VBR COS2COS2 MPLS ATM Available MPLS ATM Available Bandwidth Management

MPLS Tutorial 57 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA ATM Merge Multipoint-to-point capability Motivation —Stream Merge to achieve scalability in MPLS: –O(n) VCs with Merge as opposed to O(n2) for full mesh –Less labels required —Reduce number of receive VCs on terminals Alternatives —Frame-based VC Merge —Cell-based VP Merge

MPLS Tutorial 58 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA 111 222 33 111 222 33 Input cell streams in out 1 2 3 7 6 9 1 2 3 7 7 7 Non-VC merging (Nin–Nout) VC merging (Nin-1out) 77777777 67967796 7777777 No Cell Interleaving 7 AAL5 Cell Interleaving Problem Stream Merge

MPLS Tutorial 59 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Merge Reassembly buffers Output buffer Passport is VC-Merge Capable VC-Merge: Output Module

MPLS Tutorial 60 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA VPI=3 VPI=2 VCI=1 VPI=1 VCI=2 VCI=3 VCI=1 VCI=2 VCI=3 –merge multiple VPs into one VP –use separate VCIs within VPs to distinguish frames –less efficient use of VPI/VCI space, needs support of SVP No Cell Interleaving Problem Since VCI is Unique Option 1: Dynamic VCI Mapping Option 2: Root Assigned VCI VP-Merge

MPLS Tutorial 62 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Proposed Standard RFCs MPLS Label Stack Encoding Use of Label Switching on Frame Relay Networks Specification MPLS using ATM VC Switching Multiprotocol Label Switching Architecture

MPLS Tutorial 63 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Last Call Gone through Last Call: —Label Distribution Protocol Going to last call: —Constraint-based Label Distribution Protocol —Extensions to RSVP for LSP Tunnels —RSVP Refresh Reduction Extensions

MPLS Tutorial 65 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Nortel’s Activity IETF Interoperability Demonstration —CR-LDP Implementation —Traffic Engineering —VPN

MPLS Tutorial 66 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Progress: Consensus Plus Running Code 14 vendors & ISPs collaborated on CRLDP MPLS WG document in Orlando CRLDP is included by reference in the LDP Specification LDP Spec has gone through last call Demonstrated interoperability among three Vendors’ implementations in November ’98 CRLDP is simple, stable, robust, and easily extendible CR-LDP WG document is going to last call

MPLS Tutorial 67 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Leading Key MPLS Standards Label Distribution Protocol (LDP) —Loa Andersson & Andre Fredette Constraint-based Routing LDP (CR-LDP) —Bilel Jamoussi, Andre Fredette, Loa Andersson, Osama Abould- Magd, & Peter Ashwood-Smith QoS Resource Management in MPLS-Based Networks —Osama Aboul-Magd & Bilel Jamoussi with Jerry Ash, AT&T MPLS using ATM VP Switching —Bilel Jamoussi & Nancy Feldman, IBM Explicit Tree Routing —Swee Loke

MPLS Tutorial 68 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Hosting MPLS Multivendor Interoperability Demo MPLS over ATM Protocol implemented according to: —CRLSP over LDP Spec. —Explicit Routing (ER) —Bw Reservation —QoS signaling VC-Merge Ships in the Night Has been Tested for Interoperability with Bay BN router, Ericsson & GDC

MPLS Tutorial 69 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Demo Description Demo of five node network —Three MPLS LSRs based on ATM switches: –Ericsson AXI537, GDC Apex, Nortel Networks Passport —Two Nortel Networks MPLS LERs based on BN/ARE routers MPLS/IP links are OC3 ATM IP/Ethernet links are 10baseT All LERs/LSRs capable of LDP and CR-LDP functions

MPLS Tutorial 70 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR 3 Ericsson AXD311 A4 A3 PC2 PC1 LSR 2 Nortel Networks Passport A2 A1 A0 LSR 1 GDC APEX A5 A6A8 A4 LER 1 Nortel Networks BN/ARE A51 A41 E22 LER 2 Nortel Networks BN/ARE E22 A51 Demo Interoperability Network

MPLS Tutorial 71 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Experience Gained Clear intent and structure of LDP —Fast implementation —Simple implementation LDP flexibility —Made implementing CR-LDP easy —Frame format flexibility helped

MPLS Tutorial 72 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Promoting Open Standard www.nortelnetworks.com/mpls C Source code of LDP/CRLDP message and TLV processing According to the latest Specs: LDP: CR-LDP: Freely available to anyone Objective: promote interoperability

MPLS Tutorial 73 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Passport 6400/7400/15000 MPLS Q399 —Passport 6400/7400/15000 LSR over ATM –Strict ER –Hop-by-hop –QoS mapping –Failure handling and recovery –Interoperability with BN router —Passport 6400/7400/15000 LER –Support for terminating and initiating LSPs –FEC configuration –QoS-based mapping of traffic onto LSPs –MVR over MPLS Q499 —MPLS over Frame Relay

MPLS Tutorial 74 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR FEC LDP LER Passport 6400/7400/15000 as an LSR BN router can do the LER capability Passport current edge switch position in the network makes it an LSR candidate Passport can intemperate with Cisco at edge based on MPLS Standard LDP

MPLS Tutorial 75 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA LSR FEC LDP LER Passport 6400/7400/15000 as an LER Provides ability to interface to legacy non-MPLS literate routers and take advantage of MPLS in the network Provides support for MPLS as a transport for MVR

MPLS Tutorial 76 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS interconnecting MVRs LSPs established between CVRs Label Stacking between VRn and CVRx BGP or LDP sessions established to distribute reachability and Label

MPLS Tutorial 78 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Many drivers exist for MPLS above and beyond high-speed forwarding Summary of Motivations for MPLS Simplified forwarding based on exact match of fixed-length label –Initial drive for MPLS was based on existance of cheap, fast ATM switches Separation of routing and forwarding in IP networks –Facilitates evolution of routing techniques by fixing the forwarding method –New routing functionality can be deployed without changing the forwarding techniques of every router in the Internet Facilitates the integration of ATM and IP –Allows carriers to leverage their large investment of ATM equipment –Eliminates the adjacency problem of VC-mesh over ATM Enables the use of explicit routing/source routing in IP networks –Can be easily used for such things as traffic management, QoS routing Promotes the partitioning of functionality within the network –Move granular processing of packets to edge; restrict core to packet forwarding –Assists in maintaining scalability of IP protocols in large networks Improved routing scalability through stacking of labels –Removes the need for full routing tables from interior routers in transit domain; only routes to border routers are required Applicability to both cell and packet link-layers –Can be deployed on both cell (e.g., ATM) and packet (e.g., FR, Ethernet) media –Common management and techniques simplifies engineering

MPLS Tutorial 79 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA IP over ATM VCs ATM cloud invisible to Layer 3 Routing Full mesh of VCs within ATM cloud Many adjacencies between edge routers Topology change generates many route updates Routing algorithm made more complex ATM network visible to Layer 3 Routing Singe adjacency possible with edge router Hierachical network design possible Reduces route update traffic and power needed to process them IP over MPLS MPLS eliminates the “n-squared” problem of IP over ATM VCs IP and ATM Integration

MPLS Tutorial 80 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA A B C D Traffic engineering is the process of mapping traffic demand onto a network Demand Network Topology Purpose of traffic engineering: Maximize utilization of links and nodes throughout the network Engineer links to achieve required delay, grade-of-service Spread the network traffic across network links, minimize impact of single failure Ensure available spare-link capacity for rerouting traffic on failure Meet policy requirements imposed by the network operator Traffic engineering key to optimizing cost/performance Traffic Engineering

MPLS Tutorial 81 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Current methods of traffic engineering: Manipulating routing metrics Use PVCs over an ATM backbone Overprovision bandwidth Difficult to manage Not scalable Not economical MPLS combines benefits of ATM and IP-layer traffic engineering Chosen by routing protocol (least cost) Chosen by Traffic Eng. (least congestion) Example Network: MPLS provides a new method to do traffic engineering (traffic steering) Ingress node explicitly routes traffic over uncongested path Potential benefits of MPLS for traffic engineering: - Allows explicitly routed paths - No “n-squared” problem - Per FEC traffic monitoring - Backup paths may be configured operator control scalable granularity of feedback redundancy/restoration Congested Node Traffic Engineering Alternatives

MPLS Tutorial 82 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA MPLS can use the source routing capability to steer traffic on desired path Operator may manually configure these in each LSR along the desired path — Analogous to setting up PVCs in ATM switches Ingress LSR may be configured with the path, RSVP used to set up LSP — Some vendors have extended RSVP for MPLS path setup Ingress LSR may be configured with the path, LDP used to set up LSP — Many vendors believe RSVP not suited Ingress LSR may be configured with one or more LSRs along the desired path, hop-by-hop routing may be used to set up the rest of the path — A.k.a loose source routing, less configuration required If desired for control, route discovered by hop-by-hop routing can be frozen — A.k.a “route pinning” In the future, constraint-based routing will offload traffic engineering tasks from the operator to the network itself MPLS Traffic Engineering Methods

MPLS Tutorial 83 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA BR1 BR2 BR3 BR4 TR1 TR2 TR3 TR4 AS1 AS2 AS3 Border routers BR1-4 run an EGP, providing inter-domain routing Interior transit routers TR1-4 run an IGP, providing intra-domain routing Normal layer 3 forwarding requires interior routers to carry full routing tables — Transit router must be able to identify the correct destination ASBR (BR1-4) Carrying full routing tables in all routers limits scalability of interior routing — Slower convergence, larger routing tables, poorer fault isolation MPLS enables ingress node to identify egress router, label packet based on interior route Interior LSRs would only require enough information to forward packet to egress Ingress router receives packet Ingress router receives packet Packet labeled based on egress router Packet labeled based on egress router Forwarding in the interior based on IGP route Forwarding in the interior based on IGP route Egress border router pops label and fwds. Egress border router pops label and fwds. MPLS increases scalability by partitioning exterior routing from interior routing MPLS: Scalability Through Routing Hierarchy

MPLS Tutorial 84 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Routing Forwarding OSPF, IS-IS, BGP, RIP MPLS Forwarding Table Based on: Classful Addr. Prefix? Classless Addr. Prefix? Multicast Addr.? Port No.? ToS Field? Based on: Exact Match on Fixed-Length Label Current network has multiple forwarding paradigms — Class-ful longest prefix match (Class A,B,C boundaries) — Classless longest prefix match (variable boundaries) — Multicast (exact match on source and destination) — Type-of-service (longest prefix. match on addr. + exact match on ToS) As new routing methods change, new route lookup algorithms are required — Introduction of CIDR Next generation routers will be based on hardware for route lookup — Changes will require new hardware with new algorithm MPLS has a consistent algorithm for all types of forwarding; partitions routing/forwarding — Minimizes impact of the introduction of new forwarding methods MPLS introduces flexibility through consistent forwarding paradigm MPLS: Partitioning Routing and Forwarding

MPLS Tutorial 85 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Ethernet PPP (SONET, DS-3 etc.) ATM Frame Relay MPLS is “multiprotocol” below (link layer) as well as above (network layer) Provides for consistent operations, engineering across multiple technologies Allows operators to leverage existing infrastructure Co-existence with other protocols is provided for — e.g., “Ships in the Night” operation with ATM, muxing over PPP MPLS positioned as end-to-end forwarding paradigm Upper Layer Consistency Across Link Layers

MPLS Tutorial 86 INFORM ’99 - APRIL 11 - 16, 1999 - LAS VEGAS, NEVADA Summary MPLS is a promising emerging technology Basic functionality (Encapsulation and basic Label Distribution) has been defined by the IETF Nortel Networks is taking an active role in defining key aspects of MPLS standard and providing support of MPLS on the Bay and Nortel Networks platforms

MPLS Tutorial Bilel N. Jamoussi, Ph.D. Senior Network Architect Carrier Data Networks

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MPLS Tutorial Bilel N. Jamoussi, Ph.D. Senior Network Architect Carrier Data Networks

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