Dynamic Routing Overview 1.

Slides:



Advertisements
Similar presentations
Ver 1,12/09/2012Kode :CIJ 340,Jaringan Komputer Lanjut FASILKOM Routing Protocols and Concepts – Chapter 3 Introduction to Dynamic Routing Protocol CCNA.
Advertisements

Routing Basics.
Introduction to Dynamic Routing Protocols
Cisco S3 C5 Routing Protocols. Network Design Characteristics Reliable – provides mechanisms for error detection and correction Connectivity – incorporate.
Dynamic Routing Scalable Infrastructure Workshop, AfNOG2008.
CISCO NETWORKING ACADEMY Chabot College ELEC Routed and Routing Protocols.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Introduction to Dynamic Routing Protocol Routing Protocols and Concepts – Chapter.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.1 Routing Working at a Small-to-Medium Business or ISP – Chapter 6.
CCNA 2 v3.1 Module 6.
1 Basics of Dynamic Routing Presented by Aaron Jarvis Network Engineer.
Routing and Routing Protocols
Routing.
Chapter 5 – Routing Protocols: IGRP. Building a Network To Be Reliable – provide error detection and ability to correct errors To Provide Connectivity.
Lecture Week 3 Introduction to Dynamic Routing Protocol Routing Protocols and Concepts.
1 Semester 2 Module 6 Routing and Routing Protocols YuDa college of business James Chen
Fundamentals of Networking Discovery 2, Chapter 6 Routing.
Each computer and router interface maintains an ARP table for Layer 2 communication The ARP table is only effective for the broadcast domain (or LAN)
ROUTING BASICS. Why are Routers Necessary? One of the key components of the technical infrastructure of the network One of the key components of the technical.
Link State Routing Protocol W.lilakiatsakun. Introduction (1) Link-state routing protocols are also known as shortest path first protocols and built around.
Chapter 7: Routing Dynamically
6: Routing Working at a Small to Medium Business.
Dynamic Routing Protocols  Function(s) of Dynamic Routing Protocols: – Dynamically share information between routers (Discover remote networks). – Automatically.
Routing and Routing Protocols Routing Protocols Overview.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Introduction to Dynamic Routing Protocol Routing Protocols and Concepts.
1 Introducing Routing 1. Dynamic routing - information is learned from other routers, and routing protocols adjust routes automatically. 2. Static routing.
M.Menelaou CCNA2 ROUTING. M.Menelaou ROUTING Routing is the process that a router uses to forward packets toward the destination network. A router makes.
1 © 2003, Cisco Systems, Inc. All rights reserved. CCNA 2 Module 6 Routing and Routing Protocols.
1 © 2004, Cisco Systems, Inc. All rights reserved. CCNA 2 v3.1 Module 6 Routing and Routing Protocols.
Introduction to Dynamic Routing Protocol
1. 2 Anatomy of an IP Packet IP packets consist of the data from upper layers plus an IP header. The IP header consists of the following:
CCNA 1 Module 10 Routing Fundamentals and Subnets.
Interior Gateway Protocol. Introduction An IGP (Interior Gateway Protocol) is a protocol for exchanging routing information between gateways (hosts with.
Chapter 9. Implementing Scalability Features in Your Internetwork.
Routing Fundamental W.lilakiatsakun. Review Routing Fundamental VLSM Static & Dynamic Routing Routing algorithm concept.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Routing Protocols and Concepts Introduction to Dynamic Routing Protocol.
Page 110/27/2015 A router ‘knows’ only of networks attached to it directly – unless you configure a static route or use routing protocols Routing protocols.
More on Internet Routing A large portion of this lecture material comes from BGP tutorial given by Philip Smith from Cisco (ftp://ftp- eng.cisco.com/pfs/seminars/APRICOT2004.
CCNA 2 Week 6 Routing Protocols. Copyright © 2005 University of Bolton Topics Static Routing Dynamic Routing Routing Protocols Overview.
© 2002, Cisco Systems, Inc. All rights reserved. 1 Routing Overview.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Introduction to Dynamic Routing Protocol Routing Protocols and Concepts.
6: Routing Working at a Small to Medium Business.
IP Routing Principles. Network-Layer Protocol Operations Each router provides network layer (routing) services X Y A B C Application Presentation Session.
1 Version 3.1 Module 6 Routed & Routing Protocols.
1 7-Jan-16 S Ward Abingdon and Witney College Dynamic Routing CCNA Exploration Semester 2 Chapter 3.
Routing protocols. 1.Introduction A routing protocol is the communication used between routers. A routing protocol allows routers to share information.
Routing and Routing Protocols PJC CCNA Semester 2 Ver. 3.0 by William Kelly.
© 2002, Cisco Systems, Inc. All rights reserved..
Routing Protocols Brandon Wagner.
1 © 2004, Cisco Systems, Inc. All rights reserved. CCNA 1 Module 10 Routing Fundamentals and Subnets.
Cisco 2 - Routers Perrine modified by Brierley Page 13/21/2016 Chapter 4 Module 6 Routing & Routing Protocols.
Prof. Alfred J Bird, Ph.D., NBCT Office – Science 3rd floor – S Office Hours – Monday and Thursday.
© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.1 Routing Working at a Small-to-Medium Business or ISP – Chapter 6.
Prof. Alfred J Bird, Ph.D., NBCT Office – McCormick 3rd floor 607 Office Hours – Monday 3:00 to 4:00 and.
Routing and Routing Protocols CCNA 2 v3 – Module 6.
+ Dynamic Routing Protocols 2 nd semester
Lec4: Introduction to Dynamic Routing Protocol
Introduction to Dynamic Routing Protocol
Working at a Small-to-Medium Business or ISP – Chapter 6
Computer Networks Routing Algorithms.
CCNA 2 v3.1 Module 6 Routing and Routing Protocols
Introduction to Dynamic Routing Protocol
Routing.
Chapter 5: Dynamic Routing
Chapter 7: Routing Dynamically
Introduction to Dynamic Routing Protocol
Dynamic Routing and OSPF
Routing Protocols Charles Warren.
Working at a Small-to-Medium Business or ISP – Chapter 6
Computer Networks Protocols
Routing.
Presentation transcript:

Dynamic Routing Overview 1

Desirable Characteristics of Dynamic Routing Automatically detect and adapt to topology changes Provide optimal routing Scalability Robustness Simplicity Rapid convergence Some control of routing choices e.g., which links we prefer to use 2

Routers Talk Routing Protocols IGP / EGP 1 2 3 0111 value in arriving packet’s header routing algorithm local forwarding table header value output link 0100 0101 1001 1 2 3 0111 value in arriving packet’s header routing algorithm local forwarding table header value output link 0100 0101 1001 3

Interplay between routing & forwarding Routing Protocol IGP / EGP routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 1 value in arriving packet’s header 1 0111 2 3

IP Routing – finding the path Path is derived from information received from the routing protocol Several alternative paths may exist best next hop stored in forwarding table Decisions are updated periodically or as topology changes (event driven) Decisions are based on: topology, policies and metrics (hop count, filtering, delay, bandwidth, etc.) 5

IP Forwarding Router makes decision on which interface a packet is sent to Forwarding table populated by routing process Forwarding decisions: Destination address Class of service (fair queuing, precedence, others) Local requirements (packet filtering) 6

Convergence – why do I care? Convergence is when all the routers have a stable view of the network When a network is not converged there is network downtime Packets don’t get to where they are supposed to go Black holes (packets “disappear”) Routing Loops (packets go back and forth between the same devices) Occurs when there is a change in state of router or the links 7

Internet Routing Hierarchy The Internet is composed of Autonomous Systems Each Autonomous System is an administrative entity that Uses Interior Gateway Protocols (IGPs) to determine routing within the Autonomous System Uses Exterior Gateway Protocols (EGPs) to interact with other Autonomous Systems

IGPs and EGPs IGPs provide routing information within your network (LAN, backbone links,etc) EGPs consider other networks outside your AS as a black box.

Internet Routing Architecture Autonomous System (AS) Autonomous System (AS) Autonomous System (AS) Autonomous System (AS) Autonomous System (AS) Autonomous System: A collection of IP subnets and routers under the same administrative authority. Interior Routing Protocol Exterior Routing Protocol

Interior Gateway Protocols Four well known IGPs today RIP EIGRP OSPF ISIS 11

Exterior Gateway Protocols One single de-facto standard: BGP 12

Routing’s 3 Aspects Acquisition of information about the IP subnets that are reachable through an internet static routing configuration information dynamic routing information protocols (e.g., BGP4, OSPF, RIP, ISIS) each mechanism/protocol constructs a Routing Information Base (RIB)

Routing Aspect #2 Construction of a Forwarding Table synthesis of a single table from all the Routing Information Bases (RIBs) information about a destination subnet may be acquired multiple ways a precedence is defined among the RIBs to arbitrate conflicts on the same subnet Also called a Forwarding Information Base (FIB)

Routing #3 Use of a Forwarding Table to forward individual packets selection of the next-hop router and interface hop-by-hop, each router makes an independent decision

Routing versus Forwarding Routing = building maps and giving directions Forwarding = moving packets between interfaces according to the “directions” 3 16

IP Forwarding S D Forwarding decisions: IP Subnet IP Subnet IP Subnet Source S IP Subnet IP Subnet IP Subnet Destination IP Subnet D Forwarding decisions: Destination address class of service (fair queuing, precedence, others) local requirements (packet filtering)

Routing Tables Feed the Forwarding Table (BGP) RIB BGP 4 Routing Table (ISIS) RIB Forwarding Information Base (FIB) ISIS – Link State Database (Static) RIB Static Routes 18

RIB Construction Each routing protocol builds its own Routing Information Base (RIB) Each protocol handles route “costs” in its own way.

FIB Construction There is only ONE forwarding table! An algorithm is used to choose one next-hop toward each IP destination known by any routing protocol the set of IP destinations present in any RIB are collected if a particular IP destination is present in only one RIB, that RIB determines the next hop forwarding path for that destination Load balancing, if it is done, is a modification of the FIB creation. Multiple routes (usually with the same metric and usually only when there are multiple direct links to the same next-hop) are entered into the FIB and used to balance the load across the multiple links. The balancing can be done using round- robin, but a technique based on assigning hash codes to links in a round-robin fashion is typical. The has code is based on the source-destination address pair. This technique tends to keep datagrams that belong to the same communication in the order sent, thus reducing the amount of processing at the receiver.

FIB Construction Choosing FIB entries, cont.. if a particular IP destination is present in multiple RIBs, then a precedence is defined to select which RIB entry determines the next hop forwarding path for that destination This process normally chooses exactly one next-hop toward a given destination There are no standards for this; it is an implementation (vendor) decision

FIB Contents IP subnet and mask (or length) of destinations can be the “default” IP subnet IP address of the “next hop” toward that IP subnet Interface id of the subnet associated with the next hop Optional: cost metric associated with this entry in the forwarding table

IP routing Default route where to send packets if there is no entry for the destination in the routing table most machines have a single default route often referred to as a default gateway 0.0.0.0/0 matches all possible destinations, but is usually not the longest match

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1 10.1.1.1 & FF.00.00.00 vs. 10.0.0.0 & FF.00.00.00 Match! (length 8)

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1 10.1.1.1 & FF.FF.00.00 vs. 10.1.0.0 & FF.FF.00.00 Match! (length 16)

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1 10.1.1.1 & FF.00.00.00 vs. 20.0.0.0 & FF.00.00.00 No Match!

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1 10.1.1.1 & 00.00.00.00 vs. 0.0.0.0 & 00.00.00.00 Match! (length 0)

IP route lookup: Longest match routing Most of 10.0.0.0/8 except for 10.1.0.0/16 Packet: Destination IP address: 10.1.1.1 R4 R1 R2 10.1.0.0/16 Based on destination IP address R2’s IP forwarding table 10.0.0.0/8  R3 10.1.0.0/16  R4 20.0.0.0/8  R5 0.0.0.0/0  R1 This is the longest matching prefix (length 16). “R2” will send the packet to “R4”.

IP route lookup: Longest match routing Most specific/longest match always wins!! Many people forget this, even experienced ISP engineers Default route is 0.0.0.0/0 Can handle it using the normal longest match algorithm Matches everything. Always the shortest match.

Distance Vector and Link State Accumulates a metric hop-by-hop as the protocol messages traverse the subnets Link State Builds a network topology database Computes best path routes from current node to all destinations based on the topology

Distance Vector Protocols Each router only advertises to its neighbors, its “distance” to various IP subnets Each router computes its next-hop routing table based on least cost determined from information received from its neighbors and the cost to those neighbors

Why not use RIP? RIP is a Distance Vector Algorithm Listen to neighbouring routes Install all routes in routing table Lowest hop count wins Advertise all routes in table Very simple, very stupid Only metric is hop count Network is max 16 hops (not large enough) Slow convergence (routing loops) Poor robustness 33

EIGRP “Enhanced Interior Gateway Routing Protocol” Predecessor was IGRP which was classfull IGRP developed by Cisco in mid 1980s to overcome scalability problems with RIP Cisco proprietary routing protocol Distance Vector Routing Protocol Has very good metric control Still maybe used in some enterprise networks? Multi-protocol (supports more than IP) Exhibits good scalability and rapid convergence Supports unequal cost load balancing 34

Link State Protocols 35

Link State Protocols Each router “multicasts” to all the routers in the network the state of its locally attached links and IP subnets Each router constructs a complete topology view of the entire network based on these link state updates and computes its next-hop routing table based on this topology view

Link State Protocols Attempts to minimize convergence times and eliminate non-transient packet looping at the expense of higher messaging overhead, memory, and processing requirements Allows multiple metrics/costs to be used

IS-IS “Intermediate System to Intermediate System” Selected in 1987 by ANSI as OSI intradomain routing protocol (CLNP – connectionless network protocol) Based on work by DEC for DECnet/OSI (DECnet Phase V) Extensions for IP developed in 1988 NSFnet deployed its IGP based on early ISIS-IP draft 38

IS-IS (cont) Adopted as ISO proposed standard in 1989 Integrated ISIS supports IP and CLNP Debate between benefits of ISIS and OSPF Several ISPs chose ISIS over OSPF for a number of reasons. 1994-date: deployed by several larger ISPs Developments continuing in IETF in parallel with OSPF 39

OSPF Open Shortest Path First “Open” means it is public domain Uses “Shortest Path First” algorithm – sometimes called “the Dijkstra algorithm” IETF Working Group formed in 1988 to design an IGP for IP OSPF v1 published in 1989 – RFC1131 OSPF v2 published in 1991 – RFC1247 Developments continued through the 90s and today OSPFv3 based on OSPFv2 designed to support IPv6 40

Link State Algorithm Each router contains a database containing a map of the whole topology Links Their state (including cost) All routers have the same information All routers calculate the best path to every destination Any link state changes are flooded across the network “Global spread of local knowledge” 41

Summary Now know: Difference between static routes, RIP, OSPF and IS-IS. Difference between Routing and Forwarding A Dynamic Routing Protocol should be used in any ISP network Static routes don’t scale RIP doesn’t scale (and is obsolete) 42