Anne Reinarz Durham University

Outline

Outline


Introductory Remarks

Lecturer:


Introductory Remarks

Practicals:


Introductory Remarks

Assessment:


Introductory Remarks


Course Outline


Emphasis on:


Reading Material

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--- # Computer Network --- # Computer Network ### Definition: A computer network is a group of devices that are connected to one another in order to exchange information or share resources.  

What are the main components and devices?

--- ## The Internet: "nuts and bolts" view - Billions of connected computing devices: </img> - Hosts = end systems - Running network apps --- ## The Internet: "nuts and bolts" view
</img> - Communication links - Fiber, copper, radio, satellite - Transmission rate: bandwidth - Packet switches: forward packets (chunks of data) - Routers and switches
--- ## The Internet: "nuts and bolts" view - Internet: “network of networks” - Interconnected ISPs - Protocols control sending, receiving of messages - e.g., TCP, IP, HTTP, Skype, 802.11 - Internet standards - RFC: Request For Comments - IETF: Internet Engineering Task Force --- # What’s a protocol? --- # What’s a protocol?
Protocols define the format and order of messages sent and received among network entities, and actions taken on message transmission and receipt.

- specific messages sent - specific actions taken when messages received, or upon other events --- # What’s a protocol?
### Human protocols: - “what’s the time?” - “I have a question” - Introductions...
### Network protocols: - Machines rather than humans - All communication activity in Internet governed by protocols
--- # Protocol Examples - a human protocol and a computer network protocol: </src> --- # Access network: --- # Access network: ## digital subscriber line (DSL) </img> --- # Access network: ## digital subscriber line (DSL) - Use existing telephone line to central office DSLAM - data over DSL phone line goes to Internet - voice over DSL phone line goes to telephone net - Asymmetric access: downstream and upstream rates are different - < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) - < 24 Mbps downstream transmission rate (typically < 10 Mbps) --- # Access network: ## cable network </img> --- # Access network: ## cable network - HFC: hybrid fiber coax - asymmetric: up to 42.8 Mbps downstream transmission rate, 30.7 Mbps upstream transmission rate - Network of cable, fiber attaches homes to ISP router - homes share access network to cable headend - unlike DSL, which has dedicated access to central office --- # Enterprise access networks: ## Ethernet </img> --- # Enterprise access networks: ## Ethernet - Widely used in companies, universities, etc. - 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates - Today, end systems typically connected by Ethernet switches --- # Access network: ## home network </img> --- # Wireless access networks - Shared wireless access network connects end system to router - via base station, aka “access point” --- # Wireless access networks
</img> - Wireless LANs: - Within building (~100 ft.) - 802.11 (WiFi) - 54~1300 Mbps transmission rate
</img> - Wide-area wireless access - Provided by telco (mobile) operator, 10’s of km - Between 1 and 10 Mbps - 3G, 4G, LTE (“Long Term Evolution”), 5G
--- # Internet of Things (IoT) </img> Link --- # Physical Media --- # Physical Media - Bit - propagates between transmitter/receiver pairs - Physical link - what lies between transmitter & receiver - Guided media - signals propagate in solid media: copper, fiber, coax - Unguided media - signals propagate freely, e.g. radio --- # Physical Media ### Types of physical media: - Twisted pair (TP) - Copper wire - Coaxial cable - Fibre optic - Terrestrial radio spectrum - Satellite radio spectrum --- # Physical Media
</src> ## Twisted pair: - Two insulated copper wires - Category 5: 10 Mbps, 1 Gbps Ethernet - Category 6: 10 Gbps
</img> ## Coaxial cable: - Two concentric copper conductors - Can achieve high data transmission rates
--- # Physical Media </src> ### Fiber optic cable: - Glass fibre carrying light pulses representing bits - High-speed operation: - High-speed point-to-point transmission (e.g., 10’s-100’s Gbps transmission rate) - Low error rate: - Repeaters spaced far apart - Immune to electromagnetic noise
--- # Physical Media ### Radio
- Signal carried in electromagnetic spectrum - No physical “wire” - Carry a signal for long distances - Propagation environment effects: - Reflection - Obstruction by objects - Interference
Classified into 3 groups: - Very short distance (e.g. Bluetooth) - 5~10 metres - LAN (e.g., WiFi) - 10 to a few hundred meters - Wide-area (e.g., cellular/mobile) - Tens of miles
--- # Physical Media ### Satellite Radio Channels
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- Two types of satellites for communications: - geostationary (~36000 km above earth, stationary) - used where DSL or cable-based access is unavailable - low-earth orbiting (closer to earth, move over the surface)
--- # Network security ### Network security - How bad actors can attack computer networks - How to defend networks against attacks - How to design architectures resistant to attacks --- # Network security ### Internet originally designed with little security - Original vision: “a group of mutually trusting users attached to a transparent network” - Internet protocol designers playing “catch-up” - Security considerations in all layers! --- # Network security # Packet sniffing: - Broadcast media (shared Ethernet, wireless) - “Promiscuous” network interface reads/records all packets (e.g., including passwords!) passing by </src> - Wireshark software used in the labs is an open source packet-sniffer --- # Summary - An overview of Networks and network components - An overview of protocols - Different types of physical media for data transmission in networks - Network security ## Reference: 1. Computer Networking: A Top-Down Approach [Chapter 1]