Chapter 1 Internetworking SYBEX Inc 2001 All Rights Reserved Objectives Describe the benefits of a layered model Describe the main benefit of the OSI Reference Model Understand each of the seven layers of the OSI reference model what they provide application developers Describe flow control how it is used within an internetwork Understand how the Transport layer flow control mechanism works Describe how the OSI s Network layer provides routing in an internetwork environment List the five conversion steps of data encapsulation Compare and contrast key characteristics of LAN environments Describe the components of network devices SYBEX Inc 2001 All Rights Reserved The Basic Network The basic network allows devices to share information The term Computer Language refers to Binary code 0 s or 1 s SYBEX Inc 2001 All Rights Reserved The Basic Internetwork A router creates an internetwork SYBEX Inc 2001 All Rights Reserved Routing Protocols When you have more then one router a routing protocol is used to share network information between the routers SYBEX Inc 2001 All Rights Reserved Why Study Cisco Internetworking Access to remote computing resources Break up large networks Network Segmentation Relieve network congestion Too many hosts Broadcast storms Multicasting Low Bandwidth SYBEX Inc 2001 All Rights Reserved Why Routers Break up Broadcast domains Break up collision domains Can also be accomplished with layer 2 devices Filtering based on Layer 3 information Media Translation Quality of Service Access List control SYBEX Inc 2001 All Rights Reserved Internetworking Basics SYBEX Inc 2001 All Rights Reserved Internetworking Models The Layered Approach Advantages of Reference Models Dividing complex network operations Changing one layer without having to change all layers Allows various types of network hardware and software to communicate Defining the standard interface for plug andplay multi vendor integration SYBEX Inc 2001 All Rights Reserved The OSI Reference Model Advantages Interoperability between disparate hosts Multivendor development The OSI 1970 s is a set of guidelines that Describes how data are communicated through the network from one application to another Layer model where each of the related communication processes are included in a layer binding Provides a framework for creating implementing Network standards Devices Internetwork schemes SYBEX Inc 2001 All Rights Reserved The Upper Layers How Applications interact How data are transmitted Implemented in Hardware SYBEX Inc 2001 All Rights Reserved The Lower Layers SYBEX Inc 2001 All Rights Reserved OSI Layer Functions SYBEX Inc 2001 All Rights Reserved Application Layer Where users communicate with their PC Example Internet Explorer uses Application Level when it needs to communicate Responsible for identifying establishing the availability of the intended communication partner determining if sufficient resources exist SYBEX Inc 2001 All Rights Reserved Application Layer World Wide Web WWW E mail Gateways Electronic Data Interchange EDI Special Interest Bulletin Boards Internet Navigation Utilities Financial Transaction Services Telnet FTP SYBEX Inc 2001 All Rights Reserved Presentation Layer Presents data to the Application Layer Provides data translation coding and conversion functions Translates generically formatted data into its native format Data compression decompression encryption and decryption Ex Pict Tiff Jpeg Midi Mpeg QuickTime SYBEX Inc 2001 All Rights Reserved Session Layer Responsible for Setting up Managing Tearing down sessions between Presentation layer entities Provides dialog control between devices or nodes Simplex Half Duplex Full Duplex Keeps application data separate for other data Session Layer Protocols NFS SQL RPC X Window ASP Uses ports and sockets The address of an application on a node SYBEX Inc 2001 All Rights Reserved Transport Layer Responsible for segmenting reassembling data from upper layer applications into a data stream Multiplexes upper layer applications Session establishment Logical connection Tear down of virtual circuits End to end data transport services Hides network dependent information from the higher layers SYBEX Inc 2001 All Rights Reserved Transport Layer cont Flow Control Prevents a sending host from overflowing the buffers in the receiving host Causes of congestion Too many hosts Broadcast storms Multicasting Low Bandwidth Connection Oriented reliable Communications Segments are acknowledged Any segments NOT acknowledged are retransmitted Segments are sequenced back into proper order Manageable data flow maintained to avoid congestion data loss SYBEX Inc 2001 All Rights Reserved Establishing a Connection Oriented Session The Three way Handshake 1 2 3 SYBEX Inc 2001 All Rights Reserved Transmitting Segments with Flow Control SYBEX Inc 2001 All Rights Reserved TCP IP sets window size in bytes count SYBEX Inc 2001 All Rights Reserved Acknowledgements Ensures integrity of data stream No lost or duplicated data Positive acknowledgement with retransmission SYBEX Inc 2001 All Rights Reserved Transport Layer Reliable Delivery SYBEX Inc 2001 All Rights Reserved The Network Layer Responsible for Routing through an internetwork Between devices not locally attached Network addressing Types of Packets Data Packets Route Update Packets SYBEX Inc 2001 All Rights Reserved Routing Table Used in a Router SYBEX Inc 2001 All Rights Reserved Routing Table Entries Network Address Protocol Specific Maintain tables for each routing protocol Interface Exit interface a packet will take Metric Distance to the remote network Hop count Bandwidth Delay Etc SYBEX Inc 2001 All Rights Reserved The OSI Reference Model The Network Layer Each router interface is broadcast domain Routers break up broadcast and collision domains Provide WAN services SYBEX Inc 2001 All Rights Reserved Key Points Routers By default will not forward any broadcast or multicast packets Concerned with finding networks only Use logical addresses Can use access lists to control security Can provide layer 2 bridging simultaneously route through the same interface Layer 3 devices provide connections between Virtual LANs VLANs Can provide Quality of Service QoS for specific types of traffic Two type of packets data and route update If network cannot be found in routing table packet is dropped Ethernet header trailer stripped off at each hop SYBEX Inc 2001 All Rights Reserved The Data Link Layer Concerned with host delivery