University of Manitoba ECE 3700ECE_3700_Notes

1. Chapter 1 – Introduction 1.1. What is the internet?  Billions of connected computing devices, hosts are end systems running network apps  Communication links can be fiber, radio, satellite, and copper  Transmis ...

1. Chapter 1 – Introduction 1.1. What is the internet?  Billions of connected computing devices, hosts are end systems running network apps  Communication links can be fiber, radio, satellite, and copper  Transmission rate is referred to as bandwidth  Packet switches forward packets which are chunks of data (routers and switches)  The internet is a network of networks – it provides services to applications (like games, web, voIP, email, etc). Also provides programming interface to apps.  Protocols control sending and receiving messages (examples are TCP, IP, HTTP, Skype, 802.11) – they define format, order of messages sent and received among network entities, actions to take when receiving messages.  Internet standards: RFC (request for comments), IETF (Internet Engineering Task Force) 1.2. Network Edge  Network edge has hosts (clients and servers) and servers are often in data centers  Access networks and physical media can be wired or wireless communication links  Network core is a network of networks – composed of interconnected routers.  Access Networks: o Digital Subscriber Line (DSL)  Voice, data transmitted at different frequencies over dedicated line to central office. Uses an existing telephone line to control office DSLAM. Typically, greater than 1Mbps upstream and 10Mbps downstream rate.  Data over DSL phoneline goes to Internet, and voice over DSL phone line goes to telephone net o Cable Network  Data transmitted on shared cable but at different frequencies  Frequency division multiplexing: different channels transmitted in different frequency bands  Data transmitted at different frequency over shared cable distribution network (connected to CMTS – cable modem termination system)  HFC (hybrid fiber coax) – asymmetric; up to 30Mbps down, 2Mbps up  Network of cable, fiber attaches homes to ISP. Homes share access network to cable headend (CMTS) unlike DSL which has dedicated access to central office o Enterprise Access Networks (Ethernet)  Typically used by companies, universities. End systems typically connect to Ethernet switch.  10, 100Mbps, 1, 10Gbps transmission rates. o Wireless Access Networks  Shared wireless access network connects end system to router via base station “access point”.  Wireless LANs are within building (100ft.), 802.11b/g/n (Wifi): 11,54,450 Mbps rates Wide-area wireless access is provided by telco (cellular) operator (10km), between 1 and 10Mbps, 3G,4G, LTE.  Host sending function by taking message and breaking into chunks (packets) of L length and transmitting at rate R: Packet transmission delay = L (bits) / R (bits/sec)  Transmission rate = link capacity = link bandwidth  Physical Media