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Terms
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
Topologies
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
Topologies
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
Topologies
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
Ethernet
Ethernet is the most common LAN (Local Area Network) technology
IEEE 802.3 Developed by Digital Equipment
Corp., Intel, and Xerox. Published in 1980
Ethernet
Segment – A coaxial cable that joins all the hosts together
Collision – when two hosts try to use the connection at the same time
Ethernet
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)
Ethernet
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
WAN Technologies
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
WAN Technologies
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)
WAN Technologies
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
WAN Technologies
Packet-Switched Connections Connect to the providers network Traffic is affected by others Usual technologies are▪ Frame Relay ▪ X.25 (possible)
WAN Technologies
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)
Wireless Networks
IEEE 802.11 Advantage: Great to eliminate cables
and freedom of movement Disadvantage: range (?), reliability,
security Moderate WAN distances▪ Line of sight
Other Network Technologies
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
OSI Model
Open Systems Interconnection (OSI) model Used to standardized networking
processes No rules imposed onto the
manufacturers or protocol developers Only guidelines 7 Layers
OSI Model
7 - Application 6 - Presentation 5 - Session 4 - Transport 3 - Network 2 - Data Link 1 - Physical
Layer 7: Application
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)
Layer 6: Presentation
Responsible for formatting data so that the application layer (layer 7) can recognize and work with it.
Examples .doc .jpg .txt .avi
Layer 5: Session
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
Layer 4: Transport
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
Layer 3: Network Layer
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
Layer 3: Network Layer
With the data unit from Layer 4, the data segment is now called a packet ( or datagram)
Header has the following info:
Layer 3: Network Layer
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
Layer 3: Network Layer
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)
Layer 2: Data Link
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)
Layer 2: Data Link Layer
Not hierarchical Flat addressing
Address are done with Media Access Control (MAC)
MAC addresses are assigned in hardware
Layer 1: Physical Layer
Transmit the data onto a wire, optical fiber, or wireless
All signaling is digital Electricity On = 1 Electricity Off = 0 Typically RJ-45