The Complete IS-IS Routing Protocol

Transcription

1 Hannes Gredler and Walter Goralski The Complete IS-IS Routing Protocol 4y Springer

2 Contents Foreword Credits and Thanks vii ix 1 Introduction, Motivation and Historical Background Motivation Routing Protocols History in the 1990s DECNET Phase V NSFNetPhasel OSPF NLSP Large-scale Deployments IETFISIS-WG Sample Topology, Figures and Style 7 2 Router Architecture Architecture and the Global Routing Paradigm General Router Model Routing and Forwarding Tables Forwarding Plane Architectures Control Plane Architectures Router Technology Examples Cisco 7500 Series Cisco 7500 Series + VIP Processors Cisco GSR Series Cisco IOS Routing Software Juniper Networks M-Series Routers JUNOS Routing Software Conclusion 33 3 Introduction to the IOS and JUNOS Command Line Interface Common Properties of Command Line Interfaces (CLI) Operational Mode Configuration Mode Emacs Style Keyboard Sequences Debugging 40

3 xii Contents IP Troubleshooting Tools Routing Policy Logging Cisco Systems IOS CLI Logging into the System, Authentication, Privilege Level IS-IS-related Show Commands Interface Name-space Changing Router Configuration IS-IS-related Configuration Commands Troubleshooting Tools Routing Policy and Filtering of Routes Further Documentation Juniper Networks JUNOS CLI Logging into the System and Authentication IS-IS-related Show Commands Interface Name-space IS-IS-related Configuration Commands Changing the Configuration Activating a Configuration Troubleshooting Tools Routing Policy Further Documentation Conclusion 77 IS-IS Basics IS-IS and the OSI Reference Model Areas Levels IS-IS Routing Hierarchy Rule Route Leaking Between Levels Area Migration Scenarios Merging Areas Splitting Areas Renumbering Areas Local SPF Computation IS-IS Addressing IP Addressing IP Addressing Model OSI Addressing Examples of OSI Addressing Configuring NETs Names, System-, LAN- and LSP-IDs Summary 107

4 Contents xiii 5 Neighbour Discovery and Handshaking Hello Message Encoding LAN Hello Messages Point-to-point Hello Messages MTU Check Handshaking The 3-way Handshake on LAN Circuits The 2-way Handshake on Point-to-point Circuits The 3-way Handshake on Point-to-point Circuits Sub-net Checking Finite State Machine Neighbour Liveliness Detection IGP Helios Interface Tracking Bi-directional Fault Detection (BFD) Summary Generating, Flooding and Ageing LSPs Distributed Databases Local Computation LSPs and Revision Control Sequence Numbers LSP Lifetimes Periodic Refreshes Link-state PDUs Flooding Is Flooding Harmful? Mesh-Groups Network-wide Purging of LSPs DIS Election ' Expiration of LSPs Duplicate System-IDs Flow Control and Throttling of LSPs LSP-transmit-interval LSP-generation-interval Retransmission Interval Conclusion Pseudonodes and Designated Routers Scaling Adjacencies on Large LANs The Self-synchronization Problem Scheduling Helios Applying Jitter to Timers 185

5 xiv Contents 7.2 Pseudonodes The N 2 Problem Pseudonode Representation Pseudonode ID Selection Link-state Database Modelling Pseudonode Suppression on p2p LANs DIS and DIS Election Procedure Pre-emption Purging DIS Redundancy Summary Synchronizing Databases Why Synchronize Link-state Databases? Synchronizing Databases on Broadcast LAN Circuits Synchronizing Databases on p2p Links Periodic Synchronization on p2p Circuits Conclusion Fragmentation Fragmentation and the OSI Reference Model The Too-small MTU Problem for IP The Too-small MTU Problem for IS-IS IS-IS Application Level Fragmentation Helios (IIHs) Sequence Number Packets (SNPs) Link-state Packets (LSPs) Summary SPF and Route Calculation Route Calculation The SPF Algorithm Working Principle Example Pseudonode Processing SPF Calculation Diversity Full SPF Run Partial SPF Run Incremental SPF Run Route Resolution BGP Recursion and Route Dependency BGP Route Selection Prefix Insertion Flat Forwarding Table Hierarchical Forwarding Table Conclusion 279

6 Contents xv 11 TLVs and Sub-TLVs Taxonomy for Extensibility Current Software Maturation Models Ramifications of Non-extensible Routing Protocols What Does it Mean When a Routing Protocol Is Called Extensible? Analysis of OSPF Extensibility Analysis of IS-IS Extensibility TLV Format TLV Encoding Sub-TLVs TLV Sanity Checking Conclusion IP Reachability Information Old-style Topology (IS-Reach) Information Old-style IP Reach (RFC 1195) Information Internal IP Reachability TLV # Protocols Supported TLV # External IP Reachability TLV # Inter-Domain Information Type TLV # Interface Address TLV # IP Authentication TLV # New-style Topology (IS-Reach) Information Automatic Metric Calculation Static Metric Setting New-style Topology (IP-Reach) Information Old-, New-style Interworking Issues Domain-wide Prefix Distribution Leaking Level-2 Prefixes into Level Leaking Level-1 External Prefixes into Level Use of Admin Tags for Leaking Prefixes Conclusion IS-IS Extensions Dynamic Hostnames Authenticating Routing Information Simple Text Authentication HMAC-MD5 Authentication Weaknesses Point-to-Point Interfaces Migration Strategy Running Authentication Using IOS Running Authentication Using JUNOS Interoperability 364

7 xvi Contents 13.3 Checksums for Non-LSP PDUs PDUs Missing Checksum? Ipv6 Extensions IOS Configuration JUNOS Configuration Deployment Scenarios Multi Topology Extensions JUNOS Configuration IOS Configuration Summary and Conclusion Graceful Restart Summary Traffic Engineering and MPLS Traffic Engineering by IGP Metric Tweaking Traffic Engineering by Layer-2 Overlay Networks Traffic Engineering by MPLS Introduction to MPLS MPLS Signalling Protocols RSVP-TE Simple Traffic Engineering with RSVP-TE LDP Conclusion Complex Traffic Engineering by CSPF Computations LDP over RSVP-TE Tunnelling Forwarding Adjacencies Diffserv Aware Traffic Engineering Changed IS-IS Flooding Dynamics Conclusion Troubleshooting Methodology Tools Show Commands Debug Logs Configuration File Network Analyzers Case Studies Broken IS-IS Adjacency Injecting Full Internet Routes into IS-IS Summary Network Design Topology and Reachability Information Router Stress 479

8 Flooding SPF Stress Forwarding State Change Stress CPU and Memory Usage Design Recommendations Separate Topology and IP Reachability Data Contents Keep the Number of Active BGP Routes per Node Low Avoid LSP Fragmentation Reduce Background Noise Rely on the Link-layer for Fault Detection Simple Loopback IP Address to System-ID Conversion Schemes Align Throttling Timers Based on Global Network Delay Single Level Where You Can - Multi-level Where You Must Do Not Rely on Default Routes Use Wide-metrics Only Make Use of the Overload Bit Turn on HMAC-MD5 Authentication Turn on Graceful Restart/Non-stop Forwarding Conclusion xvii Future of IS-IS 17.1 Who Should Evolve IS-IS? 17.2 G-MPLS Problems in the Optical Network Today Cost of Transport Overlay (UNI) G-MPLS Model Peer G-MPLS Model IS-IS G-MPLS Extensions G-MPLS Summary 17.3 Multi-level (8-level) IS-IS 17.4 Extended Fragments 17.5 ibgp Peer Auto-discovery 17.6 Capability Announcement 17.7 Conclusion Index 527