ICT259 Personal Summarized Study Guide PDF

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Computer Networking (Quick Reference)Seminar 1: Fundamentals ofNetworkingServer and Clients Servers are computers with software that provides services to other end devices. Each server does have own software Clients are computers with software installed that allows them to request services from the ...

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Computer Networking (Quick Reference)

Seminar 1: Fundamentals of Networking Server and Clients Servers are computers with software that provides services to other end devices. Each server does have own software Clients are computers with software installed that allows them to request services from the server. (Like how Outlook can communicate with the email server)

Peer to Peer (P2P) Does not have a centralized server. Each computer act as a client as well as a server, able to share resources equally with other computers.

End Devices and Hosts These are network devices such as computers, tablets, smart phones and IP phones. When they are connected to any network, they are called hosts A host will be allocated with a network address and is also considered a network node.

Intermediary Network Devices They are like helper devices that assists to connect devices to a network.

They can also be used to connect different networks. Some examples are like routers, modems, firewall, switches.

Network Media Referred to as a path over which data travels from source to destination Can be wired or wireless Generally have these 3 types. Wireless LAN WAN

Network Interface Card (NIC) A circuit board that is installed on end devices to allow connections to a network via a transmission media. Physical Port and Interface A physical port on a router is referred as an interface. Eg: A NIC has a RJ45 receptacle or port. Local Area Network (LAN) A LAN is a network that links devices in a designated geographical area, like a home, office or campus. It is usually managed by a individual, or organization. Wide Area Network (WAN)

A network that spans over a large geographical area. Can be across cities, countries and continents. Usually managed by a Internet Service Provider (ISP)

Rules of Communication Protocols are used that governs and controls the communication between two devices. Both MUST use the same rules to communicate They are: 1. Message Encoding 2. Message Delivery Options 3. Message Timing 4. Message Formatting and Encapsulation 5. Message Size Message Formatting and Encapsulation A message that is sent from source to destination must use a specific format. Type of message format depends on the type of message, and the channel used to deliver the message. The data to be sent together with other information will be assembled into a frame. Encapsulation is the process of putting something around data. While decapsulation is about removing what is being added.

Message Delivery Options Three kinds of delivery options: 1. Unicast – this is a one to one method 2. Multicast – one to many 3. Broadcast – one to all Protocol Suites A set of related protocols that work together to perform a communication function Implemented by networking devices in software, hardware, and could be both. Can be seen as a stack, where each layer can have its own protocols Interaction between layers can be referred to as protocol interaction Many protocols are available in the industry.

TCP/IP Protocol Suit An open standard protocol, means that any vendor can freely implement in any hardware/software This standard ensure that products that uses these same protocols can interoperate successfully.

The Application, Transport and Internet layers are specific to TCP/IP. Network Access Layer protocols are developed by various different organizations, and are responsible for delivering the message over the physical medium

Steps of Communication Process

1. Webserver prepares HTML page as user data to be sent 2. At application layer, HTTP header is added in front of the HTML data 3. HTTP application layer will then deliver the HTML webpage data to transport layer. 4. At the transport layer, the TCP protocol adds a TCP header to form the TCP segment. This TCP segment is delivered by the TCP protocol to the Internet Layer

5. At the Internet Layer, the IP protocol adds an IP header to form IP packet. The source and destination addresses are added in the IP header. This is delivered by the IP protocol delivers to the Network Access Layer. 6.At the Network Access layer, the Ethernet protocol adds an Ethernet Header and an Ethernet Trailer to form the Ethernet frame. As the data is moved from Application to Network Access Layer, a new encapsulation process takes place. Thus for this Network Access layer, a trailer is also added. 7. At the Network Access Layer, the web client will receive the Ethernet frame in binary form. To get the user data or HTML, decapsulation is needed to be performed at each layer to get to the HTTP header. 8. Finally, the web page information is passed onto the web client’s web browser software. Reference Models A reference model is a conceptual framework for understanding relationships between various protocols. Two primarily models are, 1. Open Systems Interconnection (OSI) Model 2. TCP/IP Model Benefits of using Layered Reference Models:

- Easier to standardize, each layer focuses on specific functions, making the development of those standards easier - Lower dependence, change of one layer will not affect the others, thus allowing each layer to be developed independently. - Ensure interoperability, products from different vendors can work together - Ease of understanding, Layering protocols and functions make it clearer for people to study and research networks. OSI Reference Model Total of 7 Layers. 7 Application 6 Presentation

5 Session

4 Transport

3 Network

2 Data Link 1 Physical

TCP/IP Model

Contains protocol used for process to process communication Provides data representation to ensure the application layer of one device can identify and understand the data generated by the application layer of another device Provides services to the presentation layer to establish, manage and terminate communication sessions between two parties and determines which party can initiate the communication. Provides transparent transfer of data between end devices, responsible for end-to-end error recovery, flow control and reassembly of data. Provide node-to-node transmission over the network between identified end devices based on network layer address Describes methods for exchanging data frames between devices over a physical media Describes the mechanical, electrical, functional and procedural means to activate, maintain, and de-activate physical connections for bit transmission to and from a network device

Can be referred as an Internet Model Application

Represents data to the user and performing encoding and dialog control. User will interact with application to get info Transport Controls flow of information between app running the client and the app running the server Internet Determines best path in the network Network Access Controls hardware devices and media that makes up the network. Difference between OSI Model and TCP/IP Model Main difference is how they are divided, and protocols used. Another reason is that Internet and Network designers prefers the TCP/IP model. ## OSI Model 7 6 5 4 3 2 1

Application Presentation Session Transport Network Data Link Physical

TCP/IP Model Application

Transport Internet Network Access

TCP/IP Protocol Suite HTTP / DNS / DHCP / FTP TCP / UDP IPv4,v6,ICMPv4,v6 PPP, Frame Relay, Ethernet

As seen above, OSI layers 5,6,7 maps to the application layer of the TCP/IP Model, and is used as references for application software developers to develop network products. TCP/IP application layer protocols, provide specific functions to a variety of end user applications, like HTTP, DNS, DHCP and FTP. OSI Layer 4, transport layer, maps directly to TCP/IP transport layer. This layer is responsible for providing ordered and reliable transmission between source and destination.

OSI Layer 3, the network layer maps directly to the Internet Layer of TCP/IP model. It is responsible for addressing and routing messages through an internetwork. OSI Layer 1 and 2 describes the procedures to access the media and the physical means to transmit data over a network. At the network access layer, the TCP/IP protocol does not specific which protocols to use to send data over a physical medium. It depends rather, on the physical network.

Data Encapsulation To transmit data over the network, data will be encapsulated with appropriate addressing and control information so the data can move from source to destination. Type of information required will depend if the destination is local or at a remote network. Message Segmentation For delivery efficiency, before the data is sent from source to destination, it is broken up into smaller, manageable pieces. This is referred to as Segmentation. Each piece of these information must go through the same process to reach the destination. When all pieces have arrived at the destination, it will be reassembled into the original message. Protocol Data Units (PDU) PDU is used to describe the data unit of each layer of the model. In OSI model, the lower four layers are given specific names. Upper layers are just called Data.

The data unit can also be called as the same as the OSI layer. OSI Model PDU Name Application Data Presentation Data Session Data Transport Segment Network Packet Data Link Frame Physical Bit Encapsulation

PDU Name based on Layer Application Data Unit Presentation Data Unit Session Data Unit Transport Data Unit Network Data Unit Data Link Data Unit Physical Data Unit

In the internet Layer, the IP header will be added at the front of the TCP segment to form an IP packet. When the IP packet arrives at the Network Access Layer, assuming the layer is using Ethernet Technology, it will add an Ethernet header and trailer to the IP packet, forming the Ethernet Frame. This frame, will be covered to bit stream for transmission over the physical media to the web client Encapsulation/Decapsulation Decapsulation is the reserve process of encapsulation. When the bit stream arrives at the receiving device, protocol header is removed as it moves up the stack forward the end-user application.

Data Access In order to transmit data from source to destination, the data must be encapsulated with the correct source and destination addresses. Two types of addresses with different purposes are needed for transmission of data over a network. Ethernet MAC Address Every NIC has an unique Media Access Control (MAC) Address, which is 48 bits or 6 bytes in length. It is usually represented in 12 Hexa digits. It is also referred to as physical or hardware address of the NIC. Network and Data Link Addresses

Two types of addresses are needed for transmission of data over a network: 1. Network or Layer 3 Address, also known as end-to-end addresses – it is responsible to deliver packets from the original source to the end destination. This applies to both local and remote networks. 2. Data Link or Layer 2 Address, also known as point to point addresses – it is responsible to deliver data link frames from one NIC to another NIC on the same network. These addresses are encapsulated in a frame.

If Ethernet is used as Layer 2 and Layer 3 as IP, then Layer 2 and Layer 3 will use MAC and IP respectively. Network Addresses are known as end-to-end addresses because the network source address is the network address initiating the transmission and the network destination address of the target device that is destined to receive the message, regardless of whether the two devices are directly connected, remotely connected, or separated by many intermediary devices.

Network and Data Link Addresses on the Same Network For devices on the same network, the data link source address is the data link address of the device initiating the transmission and the data link destination address is the data link address of target device that is destined to receive the message.

The end-to-end devices is the same as the point-to-point devices, as illustrated in the example given below.

Network and Data Link Addresses on a Different Network For each network, data link source and destination addresses are the addresses of the source and destination NICs respectively, as shown below.

R1 and R2 are Ethernet interfaces and each has its own MAC and IP addresses.

Remote Network Communication Example

Node A is sending a HTTP request to a server in another network. Taking the data link protocol for LAN is Ethernet, and WAN is High-Level link control (HDLC). The protocols at the network and transport layers are IP and TCP respectively. There are three ovals shown, indicating that there are 3 different networks. Taking note that Layer 2 addressing is point to point, whereas Layer 3 addressing is end to end. Layer 3 addressing is from Node A to Server. Layer 2 addressing has 3 parts: 1. Node A to Point A (Router 1) 2. Point B to Point C (Router 1 and Router 2) 3. Point D (Router 2) to Server The HTTP request is encapsulated at Node A with: 1. TCP header to indicate that it is a web request (port 80) 2. IP header to indicate the source IP address of node A and the destination IP address of Server.1

The HTTP Request is encapsulated at Node A with:

1. Ethernet Header to indicate the source MAC address of Node A and destination MAC address of router A (the interface) 2. Ethernet trailer for error checking The Hub and Switches do not alter the source and destination MAC address in the Ethernet Header The hub, does not have any intelligence but the switch however, will switch the destination MAC address correctly. But the switch does not alter its content. When the Ethernet Frame hits Router 1, the destination IP address is examined and the router will analyze. 1. Router 1 will decide that it needs to send this frame to Router 2. 2. As this link is a HDLC WAN link, the Ethernet header and trailer is removed 3. A new HDLC header and trailer will take over it. 4. The HDLC header contains the source and destination MAC addresses of Router 1 and Router 2. 5. Rest of the frames are unchanged. When the HDLC frame hits Router 2, the router will remove the HDLC header and trailer. Router 2 will then: 1. Check internally, and decide that it needs to be forwarded into its network. 2. The IP packet is then encapsulated with Ethernet header/trailer and the source MAC address at Router 2 and destination MAC of server will be indicated in the header.

Same Network Communication Example

Node A transmit a frame to a station in the same network. Eg Node B. Since it’s the same network, the end-to-end devices is the same as point to point devices. There is also no change to any header once its encapsulated at Node A. The Ethernet header contains the source MAC of Node A and destination MAC address of Node B. The IP header contains the source IP Address of Node A and the destination IP Address of Node B. The encapsulated frame will be sent from Node A to Node B without having any change in its contents.

Seminar 2: Network Access and Ethernet Physical Layer Protocols The physical layer is responsible for transmitting data onto the physical media by encoding binary bit into signals. Physical layer protocols also define the rules for physical connections and how is the data represented on the media. These rules includes the electrical, mechanical, functional and procedural aspects of physical connections and media. These standards are implemented in hardware and are governed by many international organizations.

Network Media Three basic forms of network media: Copper Cable, Fiber-optic Cable and Wireless. Copper Media used in Networking: Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) and Coaxial.

Unshielded Twisted-Pair Cables (UTP) Widely used for LAN, terminated with RJ-45 connectors. Has eight copper wires intertwined to form four pairs of wires. These wires are encased in a flexible plastic sheath that makes it highly flexible. Shielded Twisted-Pair Cables (STP) STP cable has a shield for each pair of wires, which are then wrapped in a foil shield to protect them from electromagnetic interference. This makes them more expensive, and less flexible. Coaxial Cable Only the copper wire or center core is used to transmit signals. Usually use for cable television network systems

Unshielded Twisted-Pair Cables (UTP) Categories Classified into categories such as CAT 5 and CAT 5e (enhanced) based on the bandwidth rate they support. UTP Cable Category 3 Category 5, 5e

Category 6

Properties Used for voice communication, usually for phone lines Used for data communication, CAT 5 supports 100Mbps and up to 1000 Mbps but not recommended. CAT5e supports 1000Mbps Used for data communication, CAT 5 supports 1000Mbps and up to 10 Gbps but not recommended.

Types of UTP Cables Straight-Through UTP, widely used for networking, used to connect host  hub/switch and a switch  router. Cross-Over UTP, used to connect similar devices, ie: Router  Router, host  host. It can also be used to connect a host  router. Rollover UTP, used to connect a PC to the console port of a CISCO switch for configuration purposes.

IEEE 802 IEEE is a standard organization dedicated to create standards for many industries. As for IEEE 802, it is a family of standards for local area and metropolitan area networks. These are the commonly used 802 standards:

1. 802.3 Ethernet 2. 802.11 Wireless LAN (WAN) 3. 802.15 Wireless Personal Area Network (Like Bluetooth) 4. 802.16 Broadband Wireless Access Type of Wireless Media The wireless standards cover both physical and data link layers. 1. Wifi (IEEE 802.11 standard) – Wireless LAN (WLAN) Technology 2. Bluetooth (IEEE 802.15 standard) – Wireless Personal Area Network (WPAN), allows devices to communicate with one another over distances up to 100meters. 3. WiMAX (IEEE 802.16) Short for Worldwide Interoperability for Microwave Access. Refers to 4G wireless internet, and is a wireless broadband.

Wireless LAN For a wireless LAN to work, it requires: 1. Wireless Access Point (AP) – A device that allows a Wifi Device to connect to a wired Network. 2. Wireless NIC Adapters – A wireless NIC adapter is a wireless network interface card used to connect to a radio frequency or RF network.

Data Link Layer Protocols Purpose: Prepare data for physical layer Responsibility: Allow upper layers to access physical media Accept network layer packets and package them into frames

Prepare the data for physical network Control how data is placed and received on physical media Exchange frames between nodes over a physical media Remove data link layer header and trailer and pass packet to the network layer protocol Perform error detection

Data Link Sublayers 1. Logical Link Control (LLC) 2. Media Access Control (MAC) Logical Link Control (LLC) This upper sublayer interacts with the network layer. Created to provide different physical layer technologies, like Ethernet, Wifi, Bluetooth. A single method of accessing the network layer and beyond. Therefore, the LLC sublayer is technology independent. Network Data Link

Network Layer LLC Sublayer MAC Sublayer

Physical

Ethernet

Physical Layer

Media Access Control (MAC) This lower sublayer transits down to the physical media

Wifi

Bluetoot h

If multiple computers can access it, then some form of orderly access to the media needs to be made. This is the job of the MAC sublayer to determine which computer can access the data at the given time. Provides the data link layer addressing as well. Different access methods and addressing can be used for different layer 1 technologies. Thus, it is technology dependent.

Media Access Control Method The media access control method or in short the access method is the technique used to get the fr...