Internetworking 1 C H A P T E R 2 Internetworking Basics Internetworking Model The OSI Reference Model Ethernet Networking Wireless Networking Data Encapsulation Topic 3 1
Internetwork Basic 4 Possible causes of LAN traffic congestion are Too many hosts in a broadcast domain Broadcast storms Multicasting Low bandwidth Adding hubs for connectivity to the network A large amount of ARP or IPX traffic (IPX is a Novell 5 2
Network Segmentation 6 Collision domain Broadcast domain 7 3
Two advantages of using routers in your network are They don t forward broadcasts by default. They can filter the network based on layer 3 (Network layer) information (i.e., IP address). 8 Four router functions in your network can be listed as Packet switching Packet filtering Internetwork communication Path selection 9 4
Internetworking Model The Layered Approach Advantages of Reference Models It divides the network communication process into smaller and simpler components, thus aiding component development, design, and troubleshooting. It allows multiple-vendor development through standardization of network components. It encourages industry standardization by defining what functions occur at each layer of the model. It allows various types of network hardware and software to communicate. It prevents changes in one layer from affecting other layers, so it does not hamper development. 10 The OSI Reference Model The upper layers 11 5
The lower layers 12 Layer functions 13 6
Interfaces: Vertical (Adjacent Layer) Communication 14 Assi st.pr of. Itaru n Piti Protocols: Horizontal (Corresponding Layer) Communication 15 Assi st.pr of. Itaru n Piti 7
Data Encapsulation 16 Assi st.pr of. Itaru n Piti TCP/IP Protocols 17 Assi st.pr of. Itaru n Piti 8
TCP/IP Protocols 18 Assi st.pr of. Itaru n Piti Protocol Data Units (PDUs) and Service Data Units (SDUs) 19 Assi st.pr of. Itaru n Piti 9
Indirect Device Connection and Message Routing 20 Assi st.pr of. Itaru n Piti Application Layer The Application layer of the OSI model marks the spot where users actually communicate to the computer. Sample -> World Wide Web (WWW) E-mail gateways 21 Electronic data interchange (EDI) Special interest bulletin boards Internet navigation utilities Financial transaction services 10
The Presentation Layer 22 It presents data to the Application layer and is responsible for data translation and code formatting. This layer is essentially a translator and provides coding and conversion functions. A successful datatransfer technique is to adapt the data into a standard format before transmission. The Session Layer The Session layer is responsible for setting up, managing, and then tearing down sessions between Presentation layer entities. This layer also provides dialogue control between devices, or nodes. It coordinates communication between systems, and serves to organize their communication by offering three different modes: simplex, half duplex, and full duplex. 23 11
The Transport Layer The Transport layer segments and reassembles data into a data stream. Services located in the Transport layer both segment and reassemble data from upper-layer applications and unite it onto the same data stream. They provide end-to-end data transport services and can establish a logical connection between the sending host and destination host on an internetwork. 24 25 The Transport layer is responsible for providing mechanisms for multiplexing upper-layer applications, establishing sessions, and tearing down virtual circuits. The Transport layer can be connectionless or connection-oriented. Some of you are probably familiar with TCP and UDP already. 12
Flow Control Data integrity is ensured at the Transport layer by maintaining flow control and by allowing users to request reliable data transport between systems. The segments delivered are acknowledged back to the sender upon their reception. Any segments not acknowledged are retransmitted. Segments are sequenced back into their proper order upon arrival at their destination. A manageable data flow is maintained in order to avoid congestion, overloading, and data loss. 26 Connection-Oriented Communication a call setup, or a three way handshake 27 13
Transmitting segments with flow control 28 Acknowledgments It guarantees that the data won t be duplicated or lost. 29 This is achieved through something called positive acknowledgment with retransmission a technique that requires a receiving machine to communicate with the transmitting source by sending an acknowledgment message back to the sender when it receives data. 14
Windowing 30 The Network Layer 31 The Network layer (also called layer 3) manages device addressing, tracks the location of devices on the network, and determines the best way to move data, which means that the Network layer must transport traffic between devices that aren t locally attached. Two types of packets are used at the Network layer: Data packets : routed protocol Route update packets : routing protocol 15
Routing table used in a router 32 Here are some points about routers that you should really commit to memory: 33 Routers, by default, will not forward any broadcast or multicast packets. Routers use the logical address in a Network layer header to determine the next hop router to forward the packet to. Routers can use access lists, created by an administrator, to control security on the types of packets that are allowed to enter or exit an interface. Routers can provide layer 2 bridging functions if needed and can simultaneously route through the same interface. Layer 3 devices (routers in this case) provide connections between virtual LANs (VLANs). Routers can provide quality of service (QoS) for specific types of network traffic. 16
The Data Link Layer 34 The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control. The Data Link layer formats the message into pieces, each called a data frame, and adds a customized header containing the hardware destination and source address. Data Link layer with the Ethernet and IEEE specifications. 35 17
The IEEE Ethernet Data Link layer has two sublayers: 36 Media Access Control (MAC) 802.3 Defines how packets are placed on the media. Contention media access is first come/first served access where everyone shares the same bandwidth hence the name. Physical addressing is defined here, Logical Link Control (LLC) 802.2 Responsible for identifying Network layer protocols and then encapsulating them. Switches and Bridges at the Data Link Layer Layer 2 switching is considered hardware-based bridging because it uses specialized hardware called an application-specific integrated circuit (ASIC). 37 18
The Physical Layer 38 we find that the Physical layer does two things: It sends bits and receives bits. Bits come only in values of 1 or 0 a Morse code with numerical values. The Physical layer specifies the electrical, mechanical, procedural, and functional requirements for activating, maintaining, and deactivating a physical link between end systems. This layer is also where you identify the interface between the data terminal equipment (DTE) and the data communication equipment (DCE). Hubs at the Physical Layer A hub is really a multiple-port repeater. A repeater receives a digital signal and reamplifies or regenerates that signal, and then forwards the digital signal out all active ports without looking at any data. 39 19
Ethernet Networking 40 L E C T U R E 2-2 The success of Ethernet is due to the following factors: Simplicity and ease of maintenance Ability to incorporate new technologies Reliability Low cost of installation and upgrade 41 20
802.3 Ethernet in Relation to The OSI Model 42 IEEE 802.x Standards 43 21
Ethernet Technologies Mapped to the OSI model 44 Ethernet Addressing 45 We get into how Ethernet addressing works. It uses the Media Access Control (MAC) address burned into each and every Ethernet Network Interface Card (NIC). 22
MAC Address Format 46 Generic Frame Format 47 23
IEEE 802.3 48 Ethernet II Frame Format 49 24
Ethernet II and IEEE 802.3 Frame Format 50 Media Access Control (MAC) 51 25
MAC Rules and Collision Detection/Backoff 52 MAC Rules and Collision Detection/Backoff 53 26
Ethernet Timing 54 Interframe Spacing 55 27
Backoff 56 Error Handling 57 28
Types of Collisions 58 The effects of having a CSMA/CD network sustaining heavy collisions include Delay Low throughput Congestion 59 29
Ethernet Errors 60 Ethernet Errors 61 30
FCS Errors 62 Parameters for 10 Mbps Ethernet Operation 63 31
Manchester Encoding Examples 64 Parameters for 100-Mbps Ethernet Operation 65 32
MLT-3 Encoding Example (100Base-TX) 66 NRZI Encoding Examples (100Base-FX) 67 33
Parameters for Gigabit Ethernet Operation 68 Actual 1000Base-T Signal Transmission 69 34
Gigabit Ethernet Layers 70 Gigabit Ethernet Media Comparison 71 35
Parameters for 10-Gbps Ethernet Operation 72 10GBASE LX-4 Signal Multiplexing 73 36
Wireless Networking 74 Benefits of WLANs 75 37
Evolution of Wireless LANs 76 Unlicensed Frequency Bands 77 38
Wireless Technologies 78 Distance Versus Speed 79 39
Wireless Technologies 80 In-Building WLANs 81 40
The IEEE 802 Standards 82 IEEE 802.11 Protocols 83 41
IEEE 802.11 Standards 84 Data Encapsulation 85 42
Data Encapsulation 86 87 43
88 Summary 89 OSI model the seven-layer model used to help application developers design applications that can run on any type of system or network. Each layer has its special jobs and select responsibilities within the model to ensure that solid, effective communications do, in fact, occur. Remember that hubs are Physical layer devices and repeat the digital signal to all segments except the one it was received from. Switches segment the network using hardware addresses and break up collision domains. Routers break up broadcast domains (and collision domains) and use logical addressing to send packets through an internetwork. 44