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Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Network Models Chapter 2 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Objectives • Describe how models such as the OSI sevenlayer model and the TCP/IP model help technicians understand and troubleshoot networks • Explain the major functions of network hardware with the OSI seven-layer model • Describe the major functions of networks with the TCP/IP model © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Overview © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The CompTIA Network+ challenge • Understand every aspect of networking – Use the Open Systems Interconnect (OSI) model – Understand the TCP/IP model – Conceptualize the parts of a network © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • The OSI seven-layer model provides – A powerful tool for diagnosing problems – A common language to describe networks © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.1 Using the OSI terminology – Layer 3 – in a typical setup screen © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Working with models © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Biography of a model • What does “model” mean to you? – Computer models that predict weather – Plastic model airplane – Fashion model Figure 2.2 Types of models © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) A model has all the major functions of the real item Figure 2.3 Simple model airplane © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The OSI seven-layer model • What functions define all networks? • What details can be omitted? • ISO (International Organization for Standardization) proposed the OSI seven-layer model © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Layer 7 - Application The seven layers in action Layer 6 - Presentation Layer 5 - Session Layer 4 - Transport The OSI model Layer 3 - Network Layer 2 - Data Link Layer 1 - Physical © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The TCP/IP model • Another model that we will describe in depth a bit later in the chapter • Describes the actual de-facto protocol of the Internet • Maps to the OSI model very well © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Welcome to MHTechEd! A conceptual viewpoint of networking – One of the workers has just completed a new employee handbook – She needs to transfer the Word document to the other worker for review © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Figure 2.4 Janelle and Dana, hard at work Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) She could… • Copy the file to a flash drive and walk it over to the other person (Sneakernet) • Transfer the file using the network © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Let’s get physical... network hardware and Layers 1 – 2 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Cabling • Most networks use a cable, like this one, as a physical channel to move the bits of data unshielded twisted pair (UTP) cable Figure 2.5 UTP cabling © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Hubs • Each computer system has a cable leading to a device called a hub – Usually located in a closet • The hub sends the data received from one system to all the other systems attached to it Figure 2.6 Typical hub © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.7 The network so far, with the Physical layer hardware © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Network Interface Cards • Network Interface Cards (NICs) are installed in PCs • Network cables attach to the NICs Figure 2.8 Typical NIC © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) NIC to hub connections • Cables run from the NIC in the PC to a jack on the wall • Cables run through the walls to the closet where they connect to a hub Figure 2.9 NIC with cable connecting the PC to the wall jack © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Network cabling system Figure 2.10 The MHTechEd network © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The NIC • Each system must have a unique identifier • Media Access Control (MAC) address MAC address printed on surface of chip – and burned inside the chip. – A unique address burned into a ROM chip on the network card – Each MAC address is 12 hex characters or 48 bits in length Figure 2.11 MAC address © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) MAC addresses • MAC addresses are 48 bits long • Usually represented using hexadecimal characters (12 hex digits = 48 bits) – A typical MAC address: 004005-607D49 Organizationally unique identifier (OUI) Note: This is an IEE standard, called EUI-48! Device ID No two MAC addresses are ever the same! © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) ipconfig /all MAC address Figure 2.12 Output from ipconfig /all © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Moving data Figure 2.13 Data moving along a wire © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Moving data (cont.) Figure 2-14: Oscilloscope of data © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Moving data (cont.) Figure 2.15 Data as ones and zeroes © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Frames Figure 2-16 Inside the NIC © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Inside a frame • Frames are made up of fields that contain information • Frames contain the recipient’s MAC address, the sender’s MAC address, the data itself, and a frame check sequence (FCS) for error checking Figure 2.17 Generic frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Frame as a canister Figure 2.18 Frame as a canister Note: 2nd MAC address is wrong © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Frame size • Different networks use different sizes of frames • Many frames hold about 1500 bytes of data • The sending software breaks up large amounts of data into smaller chunks • The receiving station must then put the chunks back together in the proper order © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Processing frames • All devices on the network see the frame, but only the device that it is addressed to will process it – Every frame is received by every NIC – The MAC address is used to decide if the frame belongs to a given device © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Getting data on the line • Since the cable is shared, only one system may speak at a time • Processes are used to keep two NICs from talking at the same time © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Incoming frame! Figure 2.19 Incoming frame! © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Getting to know you • Usually two devices have talked before, so the destination MAC address is already known • If the MAC address is not known, a broadcast message is sent over the network – The destination device will respond by sending its MAC address – A MAC broadcast address is FF-FF-FF-FF-FF-FF © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.20 Building the frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.21 Adding the data and FCS to the frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.22 Sending the frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.23 Reading an incoming frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) After the frame is received • The receiving station checks the FCS value in the frame – If the value matches what it should, then the NIC sends the data portion to the network operating system for processing – If the value does not match, the frame has errors and must be resent © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The two aspects of NICs Figure 2.24 Layer 1 and Layer 2 are now properly applied to the network © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.25 LLC and MAC, the two parts of the Data Link layer © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Beyond the single wire – network software and Layers 3 – 7 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Subnets Figure 2.26 Large LAN complete (left), and broken into two subnets (right) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • Routers are used to chop large networks up into smaller ones • Routers forward packets by logical address • An IP router (most common) forwards IP packets • Works at Layer 3, the Network layer Figure 2.27 Typical small router © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.28 MHTechEd addressing © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.29 IP Packet © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.30 IP packet in a frame (as a canister) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Frames (packets) within frames • Network software creates a packet that contains the sending and receiving IP addresses along with the data IP packet © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • The packet is enclosed within a frame that contains the sending and receiving MAC addresses Figure 2.31 IP packet in a frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Connecting to the Internet • A router connects a local network to the Internet • The local hub or switch is connected to the router • The router is connected to the Internet through a cable or phone line • The cable or phone line uses a different kind of frame, so the router strips the frame and creates a new one © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Connecting to the Internet Figure 2.32 Router removing network frame and adding one for outgoing connection © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • The router replaces the MAC address with the type of address used by the cable or phone company • The frame uses the IP address to guide it to the receiving system • The receiving router strips off the cable or phone company frame and adds the MAC address for the receiving system • The NIC strips off the MAC header and hands the frame off to the NOS © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Assembly and disassembly – Layer 4, the Transport layer • Most data is much larger than a single frame • Network protocols chop up the data into smaller packets, and give each one a sequence number • The sequence numbers are used by the receiving system to put the packets back in order, and to assemble them • This compares to the numbering of boxes by UPS © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.33 Labeling the boxes © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • Transport layer is the assembler/disassembler • Transport layer also initializes requests for packets that weren’t received in good order © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.34 OSI updated © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Talking on a network – Layer 5, the Session layer • One system may be talking to many other systems simultaneously • The software that handles these processes is called session software, working at Layer 5 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.35 Handling multiple inputs © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.36 Each request becomes a session © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.37 OSI updated © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Standardized formats – or why Layer 6, Presentation, has no friends • Presentation layer tasks solved an old problem • Macintoshes and PCs use very different formats • Standardized formats have been created that allow very different operating systems to exchange data © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.38 Different data formats were often unreadable between systems © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.39 Everyone recognizes PDF files! © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.40 OSI updated © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Network applications – Layer 7, the Application layer • Users use Application layer network applications to exchange data on a network – Network in Windows Vista/7 (My Network Places in earlier Windows) – Web browser like Internet Explorer or Mozilla Firefox – Outlook Express for e-mail • All operating systems have APIs at the Application layer for network-aware applications © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.41 Network applications at work © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.42 OSI updated © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Layer 4- Application The four-layer model The TCP/IP model © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Layer 3 - Transport Layer 2 - Internet Layer 1 - Link Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • OSI model developed due to need to standardize hundreds of protocols made by different manufacturers • In the end, one major protocols suite won out and is now the de-facto standard of network and Internet communications: Transmission Control Protocol/Internet Protocol (TCP/IP) • TCP/IP is both a protocol suite and a model © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • TCP/IP model layers map to corresponding OSI model layers • Perform the same functions and use the same terminology, protocols, services, devices, etc. • Some layers map directly to corresponding layers in OSI model, others map to multiple layers © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • TCP/IP does not have a “standards” body • Results in many interpretations and variations • Variation used for the exam is the most popular used by Microsoft, Cisco and major players • This variation uses four standard layers: – – – – Link/Network Interface Internet Transport Application © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Physical, hardware, and frames – Layer 1, the Link layer • Also called the Network Interface layer • Corresponds to Layers 1 and 2 of the OSI model • Handles “physical” elements (cabling, hubs, physical addresses, and even NICs) • Software and higher-level protocols work in higher layers of TCP/IP stack • Protocol Data Unit (PDU) is called a frame © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.43 TCP/IP Link layer compared to OSI Layers 1 and 2 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) IP addressing and routing - Layer 2, the Internet layer • Deals with any device or application that uses IP protocols and IP addressing and routing • Routers function at this layer • Maps to the Network layer (Layer 3) of the OSI model • PDU at this layer is called a packet © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.44 TCP/IP Internet layer compared to OSI Layer 3 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Segments and datagrams - Layer 3, the Transport layer • Maps to OSI Transport layer, Session layer, and some of the Application layer • Uses two protocols, TCP and UDP • Provides both connection-oriented and connectionless communications • PDUs are segments (TCP) and datagrams (UDP) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.45 TCP/IP Transport layer compared to OSI Layers 4, 5, and part of 6 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • TCP provides connection-oriented communications • Some upper-layer protocols (for example, HTTP and POP) require good, established connections to function • TCP follows a prescribed set of procedures to establish and keep a good connection – synchronizes session between transmitting and receiving hosts © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.46 Connections between e-mail client and server © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • UDP provides connectionless communications • Some upper-layer protocols do not require reliable, verified connections to function • UDP sends data without waiting to see if the receiving system is ready or able to handle it • Used primarily in audio and video streaming, DNS queries, and DHCP broadcasts © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.47 Connectionless communication with Skype (a VoIP application) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • TCP segments contain header information such as source and destination port, sequence and acknowledgement numbers, and flags to ensure that connections are established and verified • Data follows the TCP header information © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.48 TCP segment © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • UDP datagrams only have four header fields • No mechanisms built in to establish, verify, or track connections or data • Data follows the UDP header information © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.49 UDP datagram © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) The top layer - Layer 4, the Application layer • Maps to the top three layers of the OSI model • Contains many of the familiar Application layer protocols (HTTP, DNS, DHCP, and so on) • Allows Presentation layer formats, such as MIME, and Application layer APIs • Application software and APIs interface to the network via Application layer protocols © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.50 TCP/IP Application layer compared to OSI Layers 5-7 © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.51 OSI model and TCP/IP model side by side © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • Each layer of both the OSI and TCP/IP models encapsulates data by adding headers in front of the data to be able to pass it up and down the stack • Data is called or known by different names as it travels through each layer • These names are called Protocol Data Units (PDUs) © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) Figure 2.52 Data encapsulation in TCP/IP © 2012 The McGraw-Hill Companies, Inc. All rights reserved. Mike Meyers’ CompTIA Network+® Guide to Managing and Troubleshooting Networks, Third Edition (Exam N10-005) • The OSI seven-layer model is a troubleshooting tool • Example: Jane can’t print to the networked printer – Layer 1 and 2: NIC shows activity? – Layer 3: Does computer have a proper IP address? – Move up through the layers to discover problem area © 2012 The McGraw-Hill Companies, Inc. All rights reserved.