CENG304 COMPUTER NETWORKS Asst. Prof. Mustafa YENIAD myeniad@ybu.edu.tr
CENG304 Course Evaluation: • 1 Midterm (35%) and 1 Final (45%) exams • 2 Quizes (20%) (Dates will be announced over google group) • Course’s Google Groups Name:
ceng304_2017
(Don’t forget to join!)
• Networking Platfom: Linux CentOS 6.8 Virtualization Environment: VMware Workstation At the end of the course, also you’ll be able to set up and
configurate common networking services such as DHCP, DNS, WEB, SSH, FTP on a Linux server. Also will have base information about Networking Security.
Basic Concepts of a Computer Network
Definition of a Network Network: System of lines/channels that interconnect E.g., railroad, highway, postal, telephone, social, computer Computer Network: Moves information Nodes: general-purpose computers (most nodes) Links: wires, fiber optics, wireless…
Definition of a Computer Network “a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information�
What consists of a Computer Network ?
Applications of Networks Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (www) Communication Email Message broadcast Remote computing Distributed processing (GRID Computing)
What is a Node? A printer, a server, even a laptop computer (even it’s connected wirelessly) connected to a network would be a node.
Any connected item to the network may be considered as a Node
Question ? Is Internet connectivity required for setting up a network?
Network Topology The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions. Choice affects: Network performance Network size Network collision detection
Bus Topology Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.
Also called linear bus One wire connects all nodes Terminator ends the wires Advantages
Easy to setup Small amount of wire
Disadvantages Slow Easy to crash
Star & Tree Topology The star topology is the most commonly used architecture in Ethernet LANs. When installed, the star topology resembles spokes in a bicycle wheel. Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
All nodes connect to a central hub /
switch
Packets sent to hub Hub sends packet to destination
Advantages Easy to setup One cable can not crash network Disadvantages One hub crashing downs entire network Uses lots of cable Most common topology
Ring Topology A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. The frame then continues around the ring until it finds the destination node, which takes the data out of the frame. Single ring – All the devices on the network share a single cable Dual ring – The dual ring topology allows data to be sent in both directions.
Nodes connected in a circle Tokens used to transmit data
Nodes must wait for token to send
Advantages
Time to send data is known No data collisions
Disadvantages
Slow Lots of cable
Mesh Topology The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.
Implementing the mesh topology is expensive and difficult.
All computers connected
together Internet is a mesh network Advantage
Data will always be delivered
Disadvantages Lots of cable Hard to setup
Network Components Physical Media Interconnecting Devices
Computers Networking Software Applications
Networking Devices NICs, Switches, Routers, Wireless Access Points, Firewalls, Modems‌ etc.
Computers: Clients and Servers In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests.
Networking Media Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means). Links that connect nodes Choice impacts: Speed Security Size
Wireless Fidelity
Wire Based Media Twisted-pair cabling: Most common LAN cable Called Cat5 or Cat6 Four pairs of copper cable twisted May be shielded from interference Speeds range from 1 Mbps to 1,000 Mbps
Wire Based Media Fiber-optic cable: Data is transmitted with light pulses Glass strand instead of cable Immune to interference Very secure Hard to work with Speeds up to 100 Gbps
Wireless Media Data transmitted through the air
LANs use radio waves WANs use microwave signals Easy to setup Difficult to secure
Common Network Types Local Area Network (LAN): • Contains printers, servers and computers • Systems are close to each other • Contained in one office or building • Organizations often have several LANs LAN networks connect computers together over relatively small distances, such as within a single building or within a small group of buildings.
Common Network Types Local Area Network (LAN): • In Client/Server type, one gets and one gives. • In Peer-to-Peer type, they can both give and both get. When several computers are interconnected but no computer occupies a priviliged position, the network is referred as a Peer-to-Peer network. In the Peer-to-Peer type, every computer can communicate with all other machine on the network, but in general each one stores its own files and runs its own applications.
Common Network Types Local Area Network (LAN):
?
Which types
Common Network Types Wide Area Network (WAN): WAN networks connect computers together over large physical distances, remotely connecting them over one huge network and allowing them to communicate even when far apart. The Internet is a WAN, and connects computers all around the world together. • LANs connect to WANs, such as the internet, using routers to transfer data and information quickly and securely. • WANs are usually too large to be controlled by one administrator, and so usually have collective ownership, or in the case of the internet, is publicly owned.
Common Network Types How do LANs and WANs connect? LANs, such as those within a private home, usually have a modem in their residence which is connected to an Internet Service Provider. Provider assigns an IP address to the modem, which is a unique number that is given to all devices capable of connecting to the internet, including any computers, phones or consoles within the home too. While all devices in LAN can communicate with each other without using the internet, if a device wants to communicate with another which is on another LAN, they can connect to the internet and send information over the WAN.
Common Network Types Metropolitan Area Network (MAN): There are also other types of network you may encounter. Some of these are different, but most are simply developed from LAN and WAN networks to have slight difference and adapt to different user needs.
MAN which is larger than a LAN but smaller than a WAN, and incorporates elements of both. It typically spans a town or city and is owned by a single person or company, such as a local council or a large company.
Common Network Types Campus Area Network (CAN): CAN which is larger than a LAN, but smaller than an MAN. This is typical in areas such as a university, large school or small business. It is typically spread over a collection of buildings which are reasonably local to each other. It may have an internal Ethernet as well as capability of connecting to the internet.
Common Network Types Wireless Local Area Network (WLAN): WLAN which works using wireless network technology such as Wi-Fi. This type of network is becoming more popular as wireless technology is further developed and is used more in the home and by small businesses. It means devices do not need to rely on physical cables and wires as much and can organise their spaces more effectively.
Common Network Types Storage Area Network (SAN): SAN connects servers directly to devices which store amounts of data without relying on a LAN or WAN network to do so. This can involve another type of connection known as Fibre Channel, a system similar to Ethernet which handles highperformance disk storage for applications on a number of professional networks.
Common Network Types Content Networks (CNs): Content networks (CNs) were developed to ease users' access to Internet resources. Companies may deploy basically two types of CNs: • Caching downloaded Internet information • Distributing Internet traffic loads across multiple servers
Common Network Types Intranet and Extranet: Intranet: An intranet is basically a network that is local to a company. In other words, users from within this company can find all of their resources without having to go outside of the company. An intranet can include LANs, private WANs and MANs, Extranet: An extranet is an extended intranet, where certain internal services are made available to known external users or external business partners at remote locations.
Common Network Types Internet: The Internet is the global system of interconnected mainframe, personal, and wireless computer networks that use the Internet protocol suite (TCP/IP) to link billions of devices worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, Usenet newsgroups, telephony, and peer-topeer networks for file sharing.
Common Network Types Virtual Private Network (VPN): A virtual private network (VPN) is a special type of secured network. A VPN is used to provide a secure connection across a public network, such as an internet. Extranets typically use a VPN to provide a secure connection between a company and its known external users or offices. • • •
Authentication is provided to validate the identities of the two peers. Confidentiality provides encryption of the data to keep it private from prying eyes. Integrity is used to ensure that the data sent between the two devices or sites has not been tampered with.
Next Topics: Networking Devices Networking Protocol OSI Reference Model Introducting to TCP / IP Protocol Suite