Mod 2 NetFundamentals S2022 ada (1).pptx

MODULE 2 – NETWORKING FUNDAMENTALS LOCAL AND REMOTE COMPUTERS • Local computer • Computer on which user is working • Remote computer • Computer that user controls or works on via network connection 2 LOCAL AREA NETWORK (LAN) • Network of computers and other devices confined to relatively small...

MODULE 2 – NETWORKING FUNDAMENTALS LOCAL AND REMOTE COMPUTERS • Local computer • Computer on which user is working • Remote computer • Computer that user controls or works on via network connection 2 LOCAL AREA NETWORK (LAN) • Network of computers and other devices confined to relatively small geographic space. IMPORTANT: This is an incomplete definition; we will revisit this topic after we discuss the concept of broadcast. • LANs involving many computers are usually server-based • On a server-based network, special computers (known as servers) process data for and facilitate communication between other computers on the network (known as clients) 3 NETWORK BASIC COMPONENTS • Workstation • Computer that typically runs a desktop operating system and connects to a network • Client/server architecture • Networking model in which clients use central server to share applications, devices, and data • Client/server network • Network based on client/server architecture • Network operating system • Special software designed to manage data and other resources on a server for a number of clients. As discussed earlier the standalone NOS no longer exists. We are using the term NOS to refer to the section of the operating system that deals with network communication 4 ADVANTAGES OF SERVER-BASED OVER PEER-TO-PEER NETWORKS • User login accounts and passwords can be assigned in one place • Access to multiple shared resources can be centrally granted • Servers are optimized to handle heavy processing loads and dedicated to handling requests from clients • Servers can accept connections from more than 10 hosts (here we are talking about Microsoft Windows servers) 5 ELEMENTS COMMON TO SERVER-BASED NETWORKS (1) • Client • In addition to referring to a computer on the network, may also refer to human user of client workstation • Server • Host is another name for a computer attached to a network • Network interface card (NIC) • Enables hosts to connect to the network and communicate with other computers. Usually the NIC is part of the mother board in with laptops, consumer PCs, cellular phones. Servers on the other hand will have multiple NICs 6 ELEMENTS COMMON TO ALL SERVER-BASED NETWORKS (2) • Addressing • Scheme for assigning unique identifying number to every workstation on network • The number that uniquely identifies each workstation and device on a network is its address for a specific protocol. • Each protocol has it’s own addressing method, hence a host can have multiple addresses. Examples: IP address, physical address, application port number, session number. 7 NETWORKING DEVICES • Repeater, Hub • Bridge, Switch • Router 8 REPEATERS • In general, repeaters were typically used to extend the size or length of a bus-topology network. • Repeaters take the signal from the inbound signal port and regenerate that signal out the outbound port. • In most networks (LANs), repeaters have been replaced by hubs, which have been replaced by switches. 9 HUBS • Hubs allow computers and other network devices to communicate with each other, and use a star topology. • Like a repeater, a hub regenerates the signal. • Hubs have the same disadvantage as a repeater, anything it receives on one port, it FLOODS out all other ports. • Wherever possible, hubs should be replace by switches 10 SWITCHES AND BRIDGES • Switches look a lot like hubs, but internally are much different. • Switches can learn where devices are on the network, so they do not have to flood information (frames), but can FILTER them so the information only goes out the port towards the destination device. • Switches also uses a star topology. 11 ROUTERS • A router is used to separate one LAN from another LAN. Another equivalent description is that a router connects two or more LANs. • A host on a network in order to communicate with a host on another network, must make use of routers. Next slide talks about LANs 12 LOCAL AREA NETWORK • A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building (Wikipedia). We will revise this definition later on in this course. • LANs are comprised of adjacent devices • Network devices used within a LAN: • Hub, Repeater • Switches, Bridges • Access point • Network devices used between LANs • Routers • Most common LAN technologies: • Ethernet • WiFi • Token Ring 13 NETWORK TOPOLOGIES • Network topology defines the structure of the network. We discussed the topologies in Module 1 • Physical topology: Actual layout of the wire or media. • Bus • Star • Ring • Mesh • Cellular • Logical topology: Defines how the media is accessed by the hosts for sending data. • Broadcast or multi-access (multiple hosts accessing the same media) • Token passing 14 IMPORTANCE OF BANDWIDTH • Bandwidth - The amount of information that can flow through a network connection in a given period of time. • In digital systems, the basic unit of bandwidth is bits per second (bps). • Bandwidth is the measure of how much information, or bits, can flow from one place to another in a given amount of time, or seconds. 15 NAMING CONVENTION, MAX LENGTH, BANDWIDTH Description Standard name Bandwidth Maximum length 50 Ohm coax cable 10 Base 2 10 Mbps 185m 50 Ohm thick coax cable 10 Base 5 10 Mbps 500m Unshielded twisted pair Cat 5 10 Base Tx 10 Mbps 100m Unshielded twisted pair Cat 5 100 Base Tx 100 Mbps 100m Unshielded twisted pair Cat 5 1000 Base Tx 1Gbps 100m Multimode optical fiber 62.5 nm 100 Base Fx 100Mbps 2000m Multimode Optical fiber 62.2 nm 1000 Base Sx 1Gbp 220m • Bandwidth also known as Data Rate varies depending upon: • Type of media • Type of technology and protocol (LAN, WAN, wireless, etc.) • The difference in bandwidth is caused in part by the physics of the media NOTE: The above cable types are just a few examples. 16 THROUGHPUT IS: • The actual measured bandwidth, at a specific time of day, using specific Internet routes, and while a specific set of data is transmitted on the network. • Often far less than the maximum bandwidth. The following are some of the factors that determine throughput: • Type of data being transferred • Network topology • Number of users on the network • User computer • Server computer • Overhead 17 STANDARDS 18 STANDARDS 1 • Computer Networking and the design of how data is handled as it both arrives and leaves the Host computer is described by the OSI (Open Systems Interconnect) model, often called the “OSI Framework” • The OSI model is a product of the ISO (International Standards Organization) • “It is a way of sub-dividing a communication system into smaller parts called layers. A layer is a collection of similar functions that provide services to the layer above it and receives services from the layer below it. On each layer, an instance provides services to the instances at the layer above and requests service from the layer below.” 19 ISO AND THE OSI MODEL • The International Organization for Standardization (ISO) released the OSI reference model in 1984 • “ISO. A network of national standards institutes from 140 countries “www.iso.ch 20 THE OSI MODEL https://en.wikipedia.org/wiki/OSI_model 21 OSI MODEL 1 • OSI (Open Systems Interface) was released as a suite of protocols to be used as the Internet standard. • TCP/IP soon became the standard. • The OSI reference model is the primary model for network communications. • Although there are other models in existence, most network vendors, today, relate their products to the OSI reference model, especially when they want to educate users on the use of their products. 22 OSI MODEL 2 • The OSI reference model allows you to: • understand, visualize, and troubleshoot the sending and receiving data on a network • visualize how information, or data packets, travels from application programs, through a network medium (e.g. wires, etc.), to another application program that is located in another computer on a network, even if the sender and receiver have different types of network media • Note: The Application Layer of the OSI model refers to networking applications, and not user applications. 23 THE ENCAPSULATION PROCESS 1 • Network communication originates at a source and is sent to a destination. • The following slides will illustrate this process Data • The information sent on a network is usually referred to as or data packets. • If one computer (host A) wants to send data to another computer (host B), the data must first be packaged through a process called encapsulation. 24 THE ENCAPSULATION PROCESS 2 25 THE ENCAPSULATION PROCESS 3 26 THE ENCAPSULATION PROCESS 4 27 THE ENCAPSULATION PROCESS 5 28 THE ENCAPSULATION PROCESS 6 29 THE ENCAPSULATION PROCESS 7 30 THE ENCAPSULATION PROCESS 8 31 THE ENCAPSULATION PROCESS 9 32 THE ENCAPSULATION PROCESS 10 33 THE ENCAPSULATION PROCESS 11 34 THE ENCAPSULATION PROCESS 12 35 THE ENCAPSULATION PROCESS 13 36 THE ENCAPSULATION PROCESS 14 37 THE ENCAPSULATION PROCESS 15 38 PROTOCOL DATA UNIT • Although the corresponding layers of the source (A) and destination (B) are not physically connected, the layers are logically directly connected. This is so because each layer can process only the information understood by the protocols specific to the layer, so for example the Data Link Layer can only read and process the information present in the Data Link header and trailer. • The data structures that these logical connection are carrying are called Protocol Data Units (PDUs) • In telecommunications, a protocol data unit is a single unit of information transmitted among peer entities of a computer network. A PDU is composed of protocolspecific control information and user data. In the layered architectures of communication protocol stacks, each layer implements protocols tailored to the specific type or mode of data exchange. (Source: https://en.wikipedia.org/wiki/Protocol_data_unit) 39 PDU DESCRIPTION • The Data Link layer PDU is known as a frame. The header and trailer specific to this layer “frame” the rest of the information • The Network layer PDU is known as a packet. Note that although packet is a data structure specific to the Network layer, frequently it is used in a casual discussion as a substitute for any data structure. In this course we will use packet only when we refer to the layer 3 PDU. • The Transport layer PDU is known as a segment. In some instances when discussing a specific Transport layer protocol, UDP, you may see the term datagram. This can be confusing since datagrams are also used for layer 2. Avoid using this term. • There is no PDU for the Physical layer, since it deals with a stream of bytes, regardless of the upper layers structures. • The other layers PDUs do not have a specific name. Those data structures are simply named PDUs • It is important to use the correct term. Do not refer to the Layer 2 PDU as packet or to the Layer 3 PDU as frame or segment. 40 DATA FLOW – FRAME .VS. PACKET – LET’S CLARIFY SOME THINGS! • KEY – The Packet is INSIDE the Frame • Probably one of the MOST improperly used term mix ups! • Both the frame and packet are pieces of data traveling through a network • A packet exists at layer 3 (Network Layer) of the OSI model where a frame exists at layer 2 (Data Link Layer) of the OSI model • Bridges and Switches (L2) deal with Frames whereas Packets are handled by Routers (L3) • Frames and Packets are limited by the MTU (Max Transmission Unit) size. Typically 1500 bytes for Ethernet. • Packets use the IP address for sending to a destination (doesn’t leave machine until enveloped in a Frame!) • Frames use the MAC address for sending to a destination. The Frame is what is put on the physical wire. 41 PROTOCOL DATA UNIT FOR EACH LAYER PDU Appl PDU Pre s Sess PDU Tra ns Net Segment D Lnk Ph ys Frame Packet Appl Pre s Sess Tra ns Net Ph ys A B PEER-TO-PEER COMMUNICATIONS BETWEEN CORRESPONDING LAYERS • To send data from the source to the destination, each layer of the OSI model at the source communicates with its peer layer at the destination. • This is peer-to-peer communication. • During this process, the protocols of each layer exchange information, called protocol data units (PDUs). 43 IEEE 802 DATA LINK SUBLAYERS Data Link Layer LLC sublayer MAC sublayer Physical Layer • Logical link control sublayer (LLC), multiplexes protocols running atop the data link layer. This sublayer is defined in the IEEE 802.2 specification • Media Access control (MAC) Runs CSMA/CD, addressing, frame recognition and synchronization. This sublayer is defined in the IEEE 802.3 specification • There is only one LLC sublayer. There are multiple MAC sublayers each specific to a type of media. See next slide 44 IEEE LAN SPECIFICATIONS IEEE 802.2 LLC Ethern et II (DIX) IEEE 802.3 IEEE 802.11 WIFI IEEE 802.15.1 WPAN Bluetoot h IEEE 802.16 Broadb and Wireles s access […] 45 THE OSI MODEL – THINGS TO REMEMBER • Layer 1 and 2 are the layers that deal with hardware and how the frame is sent from one system to another over the physical media. • Layers 3-7 deal with the Software in the Host computers (participating end point systems performing the network communications) and how they coordinate and send packets. • Layer 2 deals with MAC addressing (Frames) • Layer 3 deals with IP addressing (Packets) • Data moves up the OSI stack when receiving data • Data moves down the OSI stack when sending data • Layers communicate with ‘like’ layers’ in the remote system. Note the named PDUs 46 TCP REFERENCE MODEL Appl Pre s Sess Tra ns Net D Lnk Ph ys Applic ation Tran Interne t Networ k access The TCP/IP model (Transmission Control Protocol/Internet Protocol) is a model with four layers which is for both modelling current Internet architecture, and providing a set a rules that govern transmission over a TCP/IP. DARPA created it in the 1970s. It evolved from ARPANET. The TCP/IP Model is sometimes called the Internet Model the Four Layer Model, or less often the DOD Model. STANDARDS – WE CAN’T LIVE WITHOUT THEM • Hardware Standards • IEEE-SA (Institute of Electrical and Electronics Engineers Standards Association) Technical experts from around the world participate in the development of global standards. 1. Non profit organization - It has more than 395,000 members in more than 160 countries, 45% outside the United States 2. IEEE 802.1 – working group concerned with LAN/MAN architecture. Protocol layers above MAC and LLC layers. Port security with access control (802.1x) 3. IEEE 802 .3 – working group that defines the physical (L1) and data link (L2) layer’s media access control (MAC) of wired Ethernet. 1000BASET over twisted pair (802.3ab) 4. IEEE 802.11 – working group concerned with wireless local area network (WLAN) standards 48 STANDARDS – HARDWARE – THE MAC ADDRESS IS STORED IN YOUR NIC • We are going to talk A LOT about the MAC (Media Access Control) address in the next few slides. • For both Ethernet and Wireless networking frame, the way that they identify each other on the network is with the MAC address! (some think it’s the IP, but more about that later) • When you send a frame from your system, in most cases the frame begins with the MAC address of the system you are trying to contact. 49 STANDARDS – HARDWARE – MAC ADDRESS MUST COMPLY TO STANDARDS • Interoperability – For systems to work, they must all agree on the same type of electrical signals when passing data. • The NIC controller on every PC has a unique address burned into it during manufacturing, this is called the MAC (Media Access Control) • This is true for both ‘wired’ and ‘wireless’ NIC cards • The MAC address is 48 bits long. • A typical MAC address looks like this -> 00-21-6A-48-E9-C8 (this is in HEX of course, remember a HEX digit represents 4 bits, so 12*4=48!) • The first 24 bits are what identifies the NIC controller with a particular Vendor. These bits are known as the Organization Unique Identifier (OUI). 50 STANDARDS – FINDING THE VENDOR OF A NIC FROM THE MAC ADDRESS • The OUI registry is administered by IEEE • https://standards.ieee.org/products-services/regauth /oui/index.html • The OUI allows software (and humans) to identify the manufacturer of a specific network interface. • Classroom examples 51 STANDARDS – SOFTWARE •Software Standards RFC’s IP addressing Protocols 52 STANDARDS – RFC (REQUEST FOR COMMENT) – THE SOFTWARE STANDARDS • RFC’s are standards proposals that are submitted for review by the Internet Engineering Task Force (IETF) • The IETF develops Internet Standards for TCP/IP and the Internet Protocol Suite based upon RFC’s submitted. • It is an ‘open’ standards group, participation is voluntary. In some areas, the process is slow due to the following reason. • “Because it relies on volunteers and uses "rough consensus and running code" as its touchstone, results can be slow whenever the number of volunteers is either too small to make progress, or so large as to make consensus difficult, or when volunteers lack the necessary expertise. 53