1. Chi So

2.  Network – a set of devices, software, and cables that enables the exchange of information between them  Host Device – anything a person uses to access the network  Network Device – hubs, repeaters, bridges, switches, routes, and firewalls

3.  Point-to-Point – involves two hosts or devices that are directly connected to each other and to nothing else.  i.e. Serial Communication (not always)  Star – one host or device has multiple connections to other hosts. Sometimes called hub-and-spoke.  Anything that sends traffic through the hub or central device

4.  Ring – when one device is connected to the next one sequentially. The last device is connected to the first.  Not always a true circle  Data moves in a logical circle  i.e. FDDI and Token Ring  Bus – a single coaxial cable where hosts are attached at intervals.  i.e. cable internet

5.  Mesh – multiple point-to-point connections that connect each location to the others  Full Mesh – all devices are interconnected  Partial Mesh – some devices are interconnected

6.  Ethernet is the most common LAN (Local Area Network) technology  IEEE 802.3  Developed by Digital Equipment Corp., Intel, and Xerox. Published in 1980

7.  Segment – A coaxial cable that joins all the hosts together  Collision – when two hosts try to use the connection at the same time

8.  Carrier Sense Multiple Access with Collision Detection (CSMA/CD) – method for Ethernet to detect collusions.  Listen to the line ▪ If clear, start transmission ▪ If used, wait until clear  If collision occurs ▪ send jam signal ▪ Stop transmission ▪ Wait a random time before sending again (all hosts)

9.  Collision domain – a group of devices that are affected by one another’s collusions  The more hosts in a domain, the more frequent the collision  Bridges and switches help resolve this issue

10.  Half Duplex – Send or receive  Full Duplex – Send and Receive  8 wires needed. 4 is possible

11.  Wide Area Network (WAN)  Interconnect two or more LANs  Usually this service is bought from another company  4 types of WAN technologies ▪ Dedicated Lease Line ▪ Circuit-Switched Connections ▪ Packet-Switched Connections ▪ Cell-Switched Connections

12.  Dedicated Leased Line  A connection that is installed and provisioned for the exclusive use of the customer  No other customer can affect the line  Very expensive  A lot of control (QoS, other traffic management)  Usually point to point  Protocols used ▪ Point-to-Point Protocol (PPP) ▪ High-Level Data-Link Control Protcol (HDLC) ▪ Serial Line Internet Protocol (SLIP)

13.  Circuit-Switched Connections  Uses the phone company as a service provider ▪ Analog dial-up or digital ISDN connections ▪ Protocols used ▪ PPP ▪ HDLC ▪ SLIP ▪ Really slow, 19.2Kbit to 128Kbit

14.  Packet-Switched Connections  Connect to the providers network  Traffic is affected by others  Usual technologies are ▪ Frame Relay ▪ X.25 (possible)

15.  Cell-Switched Connections  Similar to packet switched  Difference is the unit size of the data is fixed (cell) ▪ In packet switched networks, data units are called (frames)  Dealing with traffic loads are typically easier and efficient  Examples ▪ Asynchronous Transfer Mode (ATM)

16.  IEEE 802.11  Advantage: Great to eliminate cables and freedom of movement  Disadvantage: range (?), reliability, security  Moderate WAN distances ▪ Line of sight

17.  Metropolitan Area Network (MAN)  Found in urban business centers  Storage Area Network (SAN)  Access an external storage array as a hard drive  Expensive  Content Networks  Making access to the information faster  Logging and controlling access to certain kinds of materials

18.  Open Systems Interconnection (OSI) model  Used to standardized networking processes  No rules imposed onto the manufacturers or protocol developers  Only guidelines  7 Layers

19.  7 - Application  6 - Presentation  5 - Session  4 - Transport  3 - Network  2 - Data Link  1 - Physical

20.  Any application or utility that store, send or retrieve data across a network  Sometimes called the user interface layer  Examples  Hypertext Transfer Protocol (HTTP)  File Transfer Protocol (FTP)  Simple Mail Transfer Protocol (SMTP)  Post Office Protocol v3 (POP3)  Network Time Protocol (NTP)  Simple Network Management Protocol (SNMP)  Domain Name Systems (DNS)  Dynamic Host Configuration Protocol (DHCP)  Secure Shell (SSH)

21.  Responsible for formatting data so that the application layer (layer 7) can recognize and work with it.  Examples .doc .jpg .txt .avi

22.  Deals with initiating and terminating network connections  Provides instructions to  Connect  Authenticate (optional)  Disconnect  Movement of data is handled by lower layers  Examples  Login for Telnet, SSH, SQL sessions, RPC

23.  One of the most important layers  Deals with how two hosts are going to send data. Two methods:  Connection-oriented (TCP) ▪ Reliable  Connectionless (UDP) ▪ Unreliable

24.  Deals with logical address (usually IP address)  Other possibilities ▪ IPX ▪ AppleTalk ▪ SNA  Addresses are assigned in software  IP hosts can communicate if they are on the same network  If different networks, need a router to communicate  Finding a way to communicate between two networks is call path determination

25.  With the data unit from Layer 4, the data segment is now called a packet ( or datagram)  Header has the following info:

26.  Since using logical addressing  Hierarchical ▪ Organized into a formal or ranked order ▪ Easy to build a big system ▪ Build smaller systems, and put them together ▪ Example: ▪ Mailing address

27.  Protocols:  Internet Protocol (IP)  IPX (Novell Netware)  Internet Connection Management Protocol (ICMP)  OSPF, IGRP, EIGRP, RIP, ISIS (Routing Protocols)  Address Resolution Protocol (ARP), Reverse ARP (RARP)

28.  Takes the Layer 3 packet and preparing a frame for the packet to be transmitted  Examples:  Ethernet  Frame Relay  Point-to-Point (PPP)  High-Level Data Link Control Protocol (HDLC)  Cisco Discovery Protocol (CDP)

29.  Not hierarchical  Flat addressing  Address are done with Media Access Control (MAC)  MAC addresses are assigned in hardware

30.  Transmit the data onto a wire, optical fiber, or wireless  All signaling is digital  Electricity On = 1  Electricity Off = 0  Typically RJ-45