1. Communication Networks Fourth Meeting

2. Types of Networks  What is a circuit network?  Two people are connected and allocated them their own physical path for the duration of the their connection.  What is packet networks?  Message is broken into many small pieces  Packets are sent separately.  Each packet has a header,  Contains address  Message data is carried in the body of the packet.  A message is successfully sent when all the packets have arrived at the destination. 1 2 3 1 2 3 2 3 1

3. What is Communication?  Telecommunication  Communication at a distance,  Normally communication over the telephone network.  Data communication  Either local or regional  Joins together data-using equipments  Communication network  Shared communication network  Support a wide range of services,  Send e-mails  Transfer and access data files  Static telephony  Mobile telephony  Watch video sequences

4. x Looking Inside a Network What is a clouds? The cloud contains detail that is unnecessary for the user’s understanding. The users on both sides of the cloud communicate with each other. How can we communicate through the cloude channel is established across the cloud.

5. International and National Networks Types of connection Satellites and Cables Why cables? Why satellite? International access links, Located at populated areas Small number of locations, Failure Equipment problems or Environmental interference. Protection Moving traffic from a failed path protection path the new path is

6. Capacity of the Network Links Asymmetric Digital Subscriber Line (ADSL). Base on Synchronous Digital Hierarchy (SDH), Takes blocks of digital data Organizes them into a signal with a higher bit-rate so they can be sent together on a line transmission system. SDH Is a hierarchy of bit-rates uses TDM (Time Division Multiplexing) techniques. Standardized bandwidth (bit-rate) include 155 Mbit/s 2.5 Gbit/s Cross-connect is an SDH switch Connect signals coming in on one link to signals going out on other links. TAT-1 The first trans-Atlantic telephone cable installed in 1956 Carry 36 simultaneous telephone calls. TAT-12 and TAT-13, 1996, Carry 60,000 phone calls. 2.5Gbps 155 Mbps

7. Connecting Networks Local area networks (LANs). Network in buildings. Has a limited range, Connect other devices Printers and Servers. Wide area network (WAN) A network that can connect widely dispersed computers or LANs together I Internet A combined network of WANs and LANs is called an Internet. Router A devices connect a LAN to a WAN, Route packets across wide area network. Convert data between LAN and WAN protocols.

8. IP network architecture IP networks sub-networks that use the Internet which uses the Internet protocol (IP). POP (Point of Presence) Universal Internet addressing scheme Access point to a LAN that access to the internet Internet service provider (ISP) The gateway to the Internet from home Autonomous System (AS) Contains of many nodes, Routers Links interior gateway protocol (IGP). Exterior gateway protocol (EGP) Routes between autonomous systems Example: Border gateway protocol (BGP) Backbones join together the nodes of autonomous systems. AS Router

9. IP network architecture AS1 AS2 Router A C DF Shamel wafi E W ABCEFDW A-ABBAAA BB-BBAAA CBE (?)-CEEE EBEE-BBB 5 9 1 B Routing Table from to

10. Ethernet architecture Initially 10 Mbps Thick co-axial cable Connected to a bus configuration. Today, 1 Gbps Connected to a star configuration. Use twisted pair cable Topologies Star topology Use a hub (repeater) Bus Hub Regenerate (bit-by-bit) each packet received Send data to every other computer. Most hubs can accept a maximum of 24 connections Can be extended by connecting two or more hubs together.

11. Collision Domain Broadcast. Easy protocol to implement to send to every PC Generates a lot of traffic Collision domain. Bridge Avoid spread data across a network Directs traffic intelligently using destination address in the packet’s header Has forwarding table Analyze source address in each packet it receives, Record which port the packet arrived on. Create a list of addresses of all the computers on the lan, and For each address, indicate which port will reach that computer. Bridge

12. Network Interface Card States Transmitting, Receiving, or Cycling its state between transmission and reception. Collision NIC detects signals simultaneously at its receives and transmit interfaces The station closest detects the collision transmits a 32-bit jam message onto the channel. NIC Waits a period of silence (9.6 μs according to IEEE 802.3 standard) Start transmitting Transmitting Wait Collision Yes Transmit jam message No