Chapter 1 Introduction to Data Communications

Introduction The second industrial revolution radically changes the way we communicate virtually eliminating information lag. The second industrial revolution radically changes the way we communicate virtually eliminating information lag. What problems does this create? What problems does this create?

Recent Communications History 1834 Samuel Morse invents the telegraph 1834 Samuel Morse invents the telegraph 1876 Alexander Graham Bell makes the first long-distance phone call (10 miles) 1876 Alexander Graham Bell makes the first long-distance phone call (10 miles) 1915 First transatlantic and transcontinental telephone service First transatlantic and transcontinental telephone service Microwave links for telephone calls 1948 Microwave links for telephone calls 1951 direct long distance dialing 1951 direct long distance dialing

Communications History Cont Fax service is introduced 1962 Fax service is introduced 1965 widespread use of satellite long distance widespread use of satellite long distance Non Bell equipment allowed on phones system 1968 Non Bell equipment allowed on phones system 1969 Picturephones 1969 Picturephones 1969 DARPAnet 1969 DARPAnet

Communications History Cont Limited long-distance competition allowed 1970 Limited long-distance competition allowed 1984 AT&T is broken up creating a regulatory boundary between local phone service and long distance 1984 AT&T is broken up creating a regulatory boundary between local phone service and long distance 1984 Cellular phone service starts 1984 Cellular phone service starts 1990’s Cellular phone service explodes 1990’s Cellular phone service explodes

Communications History Cont Telecommunications Competition and Deregulation Act replaced all federal and state telecommunications law 1996 Telecommunications Competition and Deregulation Act replaced all federal and state telecommunications law countries sign agreement to allow foreign telecommunications competition countries sign agreement to allow foreign telecommunications competition

Information Systems History 1950’s Batch processing and punch cards 1950’s Batch processing and punch cards 1970’s Real-time transaction-oriented database-driven systems emerge 1970’s Real-time transaction-oriented database-driven systems emerge 1990’s Macys is bankrupt in part due to their “old” 1970’s era IS infrastructure 1990’s Macys is bankrupt in part due to their “old” 1970’s era IS infrastructure Read comparison between Macys and WalMart Read comparison between Macys and WalMart

Components of a Network Server – a device that stores data and often performs functions in addition to storage Server – a device that stores data and often performs functions in addition to storage Client – A terminal or microcomputer from which a user or other application performs a work function Client – A terminal or microcomputer from which a user or other application performs a work function Circuit – a wire, or set of wires and devices (modem, router, switch etc…) that carry information from the client to the server Circuit – a wire, or set of wires and devices (modem, router, switch etc…) that carry information from the client to the server

Types of Networks LAN – Local Area Network LAN – Local Area Network BN – Backbone Network BN – Backbone Network MAN – Metropolitan Network MAN – Metropolitan Network WAN – Wide Area Network WAN – Wide Area Network Intranet – A network used within an organization Intranet – A network used within an organization Extranet – Access for people from outside Extranet – Access for people from outside

Network Models Used to break networks into component functions (layers) which then allows each layer to be addressed independently. Used to break networks into component functions (layers) which then allows each layer to be addressed independently. The use of layers and different standards (and standards bodies) at these layers allows great flexibility in design, and competition between manufacturers. The use of layers and different standards (and standards bodies) at these layers allows great flexibility in design, and competition between manufacturers.

OSI Model Produced in 1984 Produced in 1984 Consists of seven layers Consists of seven layers

Internet Model Similar to the OSI model Similar to the OSI model Compresses layers 5-7 into a single layer 5 Compresses layers 5-7 into a single layer 5 The textbook author claims the internet model has won the “war”. Is this true? The textbook author claims the internet model has won the “war”. Is this true?

Functions at Layer 4 (TCP) Error detection/correction Error detection/correction Linking higher layer software to the network layer Linking higher layer software to the network layer Name resolution Name resolution Breaking messages into pieces small enough to send over the network (MTU Breaking messages into pieces small enough to send over the network (MTU

Functions at Layer 3 (IP) Responsible for end-to-end routing of messages from sender to receiver Responsible for end-to-end routing of messages from sender to receiver Responsible for attaining the next address for messages as they hop from router to router across the internet Responsible for attaining the next address for messages as they hop from router to router across the internet

Functions at Layer 2 Responsible for moving messages from the sender to the receiver within a LAN. Responsible for moving messages from the sender to the receiver within a LAN. Controls the physical layer Controls the physical layer Formats the messages Formats the messages Provides error detection and correction Provides error detection and correction

Functions at Layer 1 Get the signal (electrical signal, light pulse, smoke signal) from one LAN device to the next. Get the signal (electrical signal, light pulse, smoke signal) from one LAN device to the next. This layer includes hardware devices such as modems and hubs. This layer includes hardware devices such as modems and hubs.

Two Types of Standards Formal Formal –Developed by an official industry or government agency –These are often slow in developing and follow an already existing de facto standard De facto De facto –Emerge in the marketplace and are supported by multiple vendors but have to official standing

Standards Making Bodies IEEE IEEE –The Institute of Electrical and Electronic Engineers –Professional organization based in the United States –Primarily responsible for existing LAN standards

Standards Making Bodies ITU-T ITU-T –Responsible for creating technical standards for the united nations international telecommunications union (ITU) –Open to public or private operators of communications networks from more then 200 countries –Based in Geneva Switzerland

Standards Making Bodies IETF IETF –Internet Engineering Task Force –Open to everyone –Manages consensus-building process through the use of RFC’s –Oversees creation of Internet protocols and standards

Future Trends Pervasive networking Pervasive networking Integration of voice, video and data Integration of voice, video and data New information services New information services

Chapter 2 Application Layer

Application Architectures Host-Based Architectures Host-Based Architectures –Commonly a mainframe with terminals Client-Based Architectures Client-Based Architectures –Distribute PC based architecture with the computing power at the desktop Client-Server Architecture Client-Server Architecture –Applications software divided between desktop PC’s and central servers (fat vs. thin clients)

N-tier Architectures Two-tier Two-tier –A client talks to a server (connecting to a web server) Three-tier Three-tier –A client talks to a web server which in turns queries a database server to obtain the requested data N-tier N-tier –Same concept applied N times

Advantages of Client-Server Scalability Scalability –N-tiered architecture gives a high degree of scalability Cost of infrastructure Cost of infrastructure –A set of smaller micro or mini computers and the associated software is often far less expensive then a mainframe approach

World Wide Web Create in 1989 at the CERN lab in Geneva Switzerland by Tim Berners-Lee Create in 1989 at the CERN lab in Geneva Switzerland by Tim Berners-Lee A graphical interface was developed in 1993 by a team of students led by Marc Andreessen at the NCSA lab at the University of Illinois A graphical interface was developed in 1993 by a team of students led by Marc Andreessen at the NCSA lab at the University of Illinois Adoption of the technology was immediate and rapid Adoption of the technology was immediate and rapid

Electronic Mail One of the earliest applications on the Internet (Early “killer” app) One of the earliest applications on the Internet (Early “killer” app) Cost and speed are among it’s strengths when compared with “snail mail” Cost and speed are among it’s strengths when compared with “snail mail” Important protocols and extensions to understand Important protocols and extensions to understand –SMTP (Simple Mail Transfer Protocol) –IMAP (Internet Message Access Protocol) –MIME (Multipurpose Internet Mail Extension)

Other Important Applications Listserv Listserv –A mailing list of users who have joined to discuss a topic or receive specific information updates Usenet Usenet –A repository of articles on many different subjects

Other Important Applications FTP – File Transfer Protocol FTP – File Transfer Protocol –Provides the ability to transfer data to and from systems (primarily used in conjunction with UNIX servers) Telnet Telnet –Provides the ability to login to a server from anywhere within a connected network –The name is derived from making a TELephone connection via the NETwork.

Chapter 3 Physical Layer

Components in Physical Layer Media Media –Wires, fiber-optic strands –Wireless Special-purpose devices Special-purpose devices –Modems –Repeaters/hubs

Circuits Physical Circuit Physical Circuit –Twisted pair cable, fiber, wireless link –Exclusively committed to your data Logical Circuit Logical Circuit –One of several, perhaps many circuits on a single physical circuit –Channel 12 on TV is a logical circuit, it rides on a coaxial cable or wireless (a physical circuit) along with many other logical circuits

Types of Data Digital Digital –Two possible values for any data bit (1 or 0) –In a fiber circuit a light being on could represent a “1” while off represents a “0” –In a copper circuit 5 volts could represent “1” while 0 volts represents “0” Analog Analog –Signals are shaped like sound waves and are constantly changing

Modem/Codec MOdulate/DEModulate MOdulate/DEModulate –Translates digital data into a form that can be transmitted across an analog circuit such as a standard telephone line COder/DECoder COder/DECoder –Translates analog information into a form that can be transmitted across a digital circuit

Circuit Configuration Point-to-Point Point-to-Point –A circuit with a device at each end –Home modem Multipoint Multipoint –A single device at one end with many devices at the other end with either time-slicing or circuit switching

Data Flow Simplex Simplex –One way transmission (i.e. cable TV) Half-duplex Half-duplex –Communication in both directions, only one way at a time (i.e. walkie-talkie) Full-duplex Full-duplex –Communication in both ways, at the same time (i.e. telephone)

Communication Media Guided media Guided media –Twisted-pair, coaxial, fiber-optic Wireless media Wireless media –Radio, infrared, satellite

Fiber Optic Multi mode Multi mode –Attenuation (weakening of the signal) –Dispersion (spreading of the signal) Single mode Single mode –Must use the precision of lasers as opposed to LED’s

Coding Character Character –A symbol with a constant understood meaning Byte Byte –A group of (typically) eight bits that is treated as a character ASCII (American Standard Code for Information Interchange) ASCII (American Standard Code for Information Interchange) –7 or 8 bit code (typically 8)

Transmission Modes Parallel Parallel –All bits are sent simultaneously, in a 32-bit system then there must be paths to send all 32 bits at the same time Serial Serial –Each bit is sent one at a time,

Digital Transmission Transmission of 1’s and 0’s Transmission of 1’s and 0’s –With electricity this can be voltages with perhaps 0 volts representing a zero and 5 volts representing a 1 (unipolar) –With light this can be using the state of the light with perhaps off representing a 0 and on representing a 1

Manchester Encoding Used in Ethernet Used in Ethernet Unipolar coding scheme with a twist Unipolar coding scheme with a twist –Voltage moving from a lower level to a higher level represents a “1” –Voltage moving from high to low is a “0”

Analog Transmission Telephone systems were originally designed to carry analog transmissions, electrical representations of the human voice Telephone systems were originally designed to carry analog transmissions, electrical representations of the human voice Three key characteristics Three key characteristics –Amplitude –Frequency –Phase

Modulation A carrier wave (ugly noise heard when modems are negotiating) is sent between modems, the shape of the wave is altered to represent 1’s and 0’s A carrier wave (ugly noise heard when modems are negotiating) is sent between modems, the shape of the wave is altered to represent 1’s and 0’s These “shape changes” are referred to as modulation These “shape changes” are referred to as modulation

Modulation Techniques Amplitude Amplitude –Modifying the height of the wave Frequency Frequency –Modifying the frequency (the number of waves per second) of the wave Phase Phase –Modifying the point in phase at which the wave starts

Amplitude Modulation

Frequency Modulation

Phase Modulation

Two-bit Amplitude Modulation

Modulation Techniques The various modulation techniques discussed can be combined as well The various modulation techniques discussed can be combined as well QAM (Quadrature Amplitude Modulation) QAM (Quadrature Amplitude Modulation) –Combines eight phases (three bits) and two amplitudes (one bit) for a total of four bits TCM (Trellis Code Modulation) TCM (Trellis Code Modulation) –Similar to QAM but can transmit up to ten bits per symbol

Bits Baud and Symbol Bits (specifically bits per second) are generally the important measurement in data communications as symbols are composed of bits Bits (specifically bits per second) are generally the important measurement in data communications as symbols are composed of bits There is a common misconception that these terms are interchangeable, baud refers to the number of symbols per second as opposed to the number of bits per second There is a common misconception that these terms are interchangeable, baud refers to the number of symbols per second as opposed to the number of bits per second

Voice Circuit Capacity Home analog phone lines have a bandwidth range from 0 to 4000 Hz Home analog phone lines have a bandwidth range from 0 to 4000 Hz The human ear can detect sounds up to ~14,000 Hz so very high pitch sounds can’t be transmitted over an analog phone line The human ear can detect sounds up to ~14,000 Hz so very high pitch sounds can’t be transmitted over an analog phone line Digital circuits used to tie analog phone lines together have a bandwidth of 64,000 bits per second (bps) Digital circuits used to tie analog phone lines together have a bandwidth of 64,000 bits per second (bps)

Modem Technologies V.34+ V.34+ –Transmits up to 33,600 bps V.44 (Compression) V.44 (Compression) –Builds a dictionary of character combinations being sent over the circuit –When a combination is repeated the dictionary reference is sent as opposed to the characters –Average throughput is ~ 6:1

Codec Converts Analog data into a digital form for transmission over a digital system and back Converts Analog data into a digital form for transmission over a digital system and back The analog signal is translated into a binary number The analog signal is translated into a binary number This digital signal is an approximation of the original with the quality depending on the resolution by either increasing the amplitude levels or increasing the sampling rate This digital signal is an approximation of the original with the quality depending on the resolution by either increasing the amplitude levels or increasing the sampling rate

Telephone Transmission The “local loop” is the circuit from the phone company CO (the building between 3 rd and 4 th streets and Chestnut and Hazel streets) uses analog transmission The “local loop” is the circuit from the phone company CO (the building between 3 rd and 4 th streets and Chestnut and Hazel streets) uses analog transmission Once the signal reaches the phone company office it is converted to digital form and is then sent to it’s destination CO Once the signal reaches the phone company office it is converted to digital form and is then sent to it’s destination CO Even local calls are converted to digital Even local calls are converted to digital

Pulse Code Modulation PCM is used in phone company CODEC’s in North America PCM is used in phone company CODEC’s in North America PCM samples the data 8,000 times (twice the highest frequency within the phone system PCM samples the data 8,000 times (twice the highest frequency within the phone system Eight bits are generated for each sample, thus the phone system uses the 8 bits * 8,000 samples for a data rate of 64,000 bps Eight bits are generated for each sample, thus the phone system uses the 8 bits * 8,000 samples for a data rate of 64,000 bps

ADPCM Adaptive Differential Pulse Code Modulation Adaptive Differential Pulse Code Modulation Similar to PCM except it only sends the difference between the former and the new signal Similar to PCM except it only sends the difference between the former and the new signal Data rates as low as 8Kbps can be obtained, 32Kbps is the lowest providing sufficient quality so that the user doesn’t notice Data rates as low as 8Kbps can be obtained, 32Kbps is the lowest providing sufficient quality so that the user doesn’t notice The use of ADPCM is the reason that some users can’t get a modem connection above 26,200 bps The use of ADPCM is the reason that some users can’t get a modem connection above 26,200 bps

Analog/Digital Modems Uses PCM backward Uses PCM backward Sends 8,000 samples per second Sends 8,000 samples per second Uses 7 bits (one is lost for control purposes Uses 7 bits (one is lost for control purposes 7 bits * 8,000 samples = 56,000 bits 7 bits * 8,000 samples = 56,000 bits V.92 modems do this in each direction and due to technical constraints are limited to ~52,000 bps downstream and ~42,000 bps upstream V.92 modems do this in each direction and due to technical constraints are limited to ~52,000 bps downstream and ~42,000 bps upstream

Multiplexing Using one high-speed circuit to carry the traffic of multiple lower-speed circuits Using one high-speed circuit to carry the traffic of multiple lower-speed circuits FDM FDM TDM TDM WDM (form of FDM) WDM (form of FDM) DWM (combination of FDM and TDM) DWM (combination of FDM and TDM) –Has reached 1.25 terabits already and is expected to reach 1 petabit within a few years

Frequency Division Multiplexing

Time Division Multiplexing

Inverse Multiplexing Using a series of lower-speed circuits to connect two high-speed circuits together Using a series of lower-speed circuits to connect two high-speed circuits together Technology has been proprietary until just recently Technology has been proprietary until just recently The BONDING (Bandwidth ON Demand Interoperability Networking Group) standard is allowing vendors to interoperate today but this is still in its infancy The BONDING (Bandwidth ON Demand Interoperability Networking Group) standard is allowing vendors to interoperate today but this is still in its infancy

Inverse Multiplexing

Digital Subscriber Line Much of the available bandwidth in the local loop has gone unused for many years Much of the available bandwidth in the local loop has gone unused for many years DSL uses this bandwidth by applying FDM to create three circuits comprised of the original phone line, a upstream data circuit and a downstream data circuit DSL uses this bandwidth by applying FDM to create three circuits comprised of the original phone line, a upstream data circuit and a downstream data circuit TDM and PM are also used to obtain various data rates and features TDM and PM are also used to obtain various data rates and features

Chapter 4 Data Link Layer

Media Access Control A mechanism used to control when computers transmit A mechanism used to control when computers transmit Important when using half-duplex circuits or multipoint configurations Important when using half-duplex circuits or multipoint configurations Two fundamental approaches Two fundamental approaches –Controlled Access –Contention

Controlled Access X-ON/X-OFF X-ON/X-OFF Polling Polling –Roll Call Polling: one device in the circuit is a “master” and checks with each other device on its wire to see if they have something to say –Hub Polling (token passing): one computer starts the poll and passes it to the next, when a computer with something to say receives the “token” then it can send its data

Contention The opposite of controlled access, each device listens to see if someone else is talking, if not then it sends carrier and starts to talk The opposite of controlled access, each device listens to see if someone else is talking, if not then it sends carrier and starts to talk CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is used in Ethernet networks CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is used in Ethernet networks

Network Errors Two types of network errors Two types of network errors –Data loss –Data corruption Three approaches to dealing with errors Three approaches to dealing with errors –Prevention –Detection –Correction

Sources of Errors Line noise, distortion Line noise, distortion Line outages Line outages Impulse noise Impulse noise Cross-talk Cross-talk Attenuation Attenuation Intermodulation noise Intermodulation noise Jitter Jitter

Error Prevention Shielded cabling Shielded cabling Cable location Cable location Cable selection (fiber vs. twisted pair) Cable selection (fiber vs. twisted pair) Cable installation and maintenance Cable installation and maintenance

Error Detection Parity Parity Longitudinal redundancy checking Longitudinal redundancy checking Polynomial checking Polynomial checking –Checksum –Cyclic Redundancy Check »16-bit CRC used in TCP »32-bit CRC used in Ethernet

Error Correction via Retrans. Stop-and-wait ARQ Stop-and-wait ARQ Continuous ARQ Continuous ARQ

Forward Error Correction Sufficient redundant data is included within the transmission to correct errors without retransmission Sufficient redundant data is included within the transmission to correct errors without retransmission Used heavily in satellite transmission Used heavily in satellite transmission

Ethernet Protocols Ethernet (IEEE 802.3) Ethernet (IEEE 802.3) –Byte-count protocol –Destination, length, LLC, SNAP, CRC-32 Point-to-Point Protocol (PPP) Point-to-Point Protocol (PPP) –Address –Protocol –Message length = 1,500 bytes

Bridging/Switching MAC-layer address table for each interface MAC-layer address table for each interface Addresses behind a port are stored in memory Addresses behind a port are stored in memory Ethernet frames are checked at each interface to determine if they should be forwarded Ethernet frames are checked at each interface to determine if they should be forwarded

Transmission Efficiency Transmission efficiency = total information bits/total bits Transmission efficiency = total information bits/total bits Throughput = transmission efficiency adjusted for errors and retransmissions Throughput = transmission efficiency adjusted for errors and retransmissions TRIB TRIB

Chapter 5 Network and Transport Layers

TCP/IP TCP TCP –Layer 4 –Provides error detection (CRC-16) –Breaks data into appropriate size blocks (MTU) IP IP –Provides routing and addressing –IPv4 (32-bit address) –IPv6 (128-bit address)

TCP Ports A computer can have multiple applications running, i.e. a machine can be running both a web server and an server A computer can have multiple applications running, i.e. a machine can be running both a web server and an server Commonly used ports Commonly used ports –SMTP – port 26 –WWW – port 80 –FTP – port 21 –Telnet – port 23

Packetizing Taking an outgoing message with a length too great to fit within the data-link maximum frame length (MTU) and breaking the message into appropriate lengths Taking an outgoing message with a length too great to fit within the data-link maximum frame length (MTU) and breaking the message into appropriate lengths Function is performed by the transport layer Function is performed by the transport layer With IPv4 the packet size is set for the local LAN and is adjusted if the message is sent across a link that requires a smaller MTU With IPv4 the packet size is set for the local LAN and is adjusted if the message is sent across a link that requires a smaller MTU

Connection-oriented Routing A specific route “virtual route” is determined when the session is created A specific route “virtual route” is determined when the session is created A SYN packet is sent to create the virtual circuit A SYN packet is sent to create the virtual circuit A FIN packet is sent to tear the circuit down A FIN packet is sent to tear the circuit down

Connectionless Routing Uses UDP instead of TCP Uses UDP instead of TCP Packets can travel different routes Packets can travel different routes Commonly used with applications such as DNS and DHCP which are not likely to send a packet that will have to be broken into pieces Commonly used with applications such as DNS and DHCP which are not likely to send a packet that will have to be broken into pieces

Quality of Service A special type of connection-oriented routing A special type of connection-oriented routing Classes of service are established and each application is assigned one of the classes Classes of service are established and each application is assigned one of the classes Applications such as VoIP and video- conferencing may be in a higher priority class then SMTP or WWW Applications such as VoIP and video- conferencing may be in a higher priority class then SMTP or WWW

Internet Addresses Assigned by ICANN (Internet Corporation for Assigned Numbers and Names) Assigned by ICANN (Internet Corporation for Assigned Numbers and Names) Blocks of network addresses are assigned to organizations Blocks of network addresses are assigned to organizations Often a large block of addresses are assigned to an organization Often a large block of addresses are assigned to an organization These large blocks of addresses are broken into smaller blocks referred to as “subnets” These large blocks of addresses are broken into smaller blocks referred to as “subnets”

Subnets There are many possible combinations when dividing a network address block into subnets There are many possible combinations when dividing a network address block into subnets It is also possible to merge two adjacent networks together into a single “supernet” It is also possible to merge two adjacent networks together into a single “supernet” Whether dividing a network into subnets or combining two or more networks into a supernet the subnet mask is the key Whether dividing a network into subnets or combining two or more networks into a supernet the subnet mask is the key

Subnet Mask A subnet mask is a string of 1’s and 0’s A subnet mask is a string of 1’s and 0’s A subnet mask of indicates the first three bytes of the IP address are part of the network A subnet mask of indicates the first three bytes of the IP address are part of the network Another way of looking at this subnet mask would be Another way of looking at this subnet mask would be A 1 indicates the corresponding bit in the IP address is part of the network designation A 1 indicates the corresponding bit in the IP address is part of the network designation

Dynamic Addressing DHCP (Dynamic Host Configuration Protocol) DHCP (Dynamic Host Configuration Protocol) When the computer is started it sends a message requesting that a DHCP server provide an IP address and other configuration allowing the computer to communicate via IP When the computer is started it sends a message requesting that a DHCP server provide an IP address and other configuration allowing the computer to communicate via IP

Layer 2 Address Resolution ARP (Address Resolution Protocol) ARP (Address Resolution Protocol) Broadcast Message (all 1’s) Broadcast Message (all 1’s) Whoever has IP address xxx.xxx.xxx.xxx send me your Ethernet address Whoever has IP address xxx.xxx.xxx.xxx send me your Ethernet address

Domain Name Service An Internet phone book An Internet phone book When typing in DNS will translate this application-layer address to the network-layer address of When typing in DNS will translate this application-layer address to the network-layer address of www.csuchico.edu

Routing Packets are routed between networks based on a set of routing tables Packets are routed between networks based on a set of routing tables The routing tables can be manually programmed (static routing) or created by a routing protocol (dynamic routing) The routing tables can be manually programmed (static routing) or created by a routing protocol (dynamic routing) Routing Protocols Routing Protocols –Distance Vector (RIP) –Link State (OSPF)

Routing Protocols Interior routing protocols Interior routing protocols –RIP, OSPF, EIGRP Exterior routing protocols Exterior routing protocols –OSPF, BGP Autonomous System Autonomous System

Multicasting Three types of messages Three types of messages –Unicast –Broadcast –Multicast IGMP (Internet Group Management Protocol) IGMP (Internet Group Management Protocol) –Each participating computer uses a common data-link layer address

TCP/IP Example Work through the entire TCP/IP example at the end of chapter 5 Work through the entire TCP/IP example at the end of chapter 5 –Known addresses, same subnet –Known addresses, different subnet –Unknown addresses –TCP connections

Chapter 6 Local Area Networks

Why Use a LAN? Information Sharing Information Sharing – –File access –Video conferencing Resource Sharing Resource Sharing –Printers –Applications servers

Dedicated Server vs. Peer-to-Peer Dedicated Server Dedicated Server –One or more server computers permanently assigned to being a network server »File servers »Print servers Peer-to-Peer Peer-to-Peer –No dedicated server

LAN Components NIC (Network Interface Card) NIC (Network Interface Card) Network cables Network cables –Twisted pair »UTP/STP »See Category Ratings in Technology Focus –Coaxial cables »BALUNs –Fiber-optic cables »Single-mode vs. multi-mode

LAN Components Cont. Network hubs Network hubs Network bridges/switches Network bridges/switches Network routers Network routers Network Operating System Network Operating System –Server/client software Network profile Network profile Storage Area Networks (SAN) Storage Area Networks (SAN) Network Attached Storage (NAS) Network Attached Storage (NAS)

Ethernet (IEEE 802.3) Topology Topology –Logical vs. physical The logical topology of a traditional Ethernet network is a bus The logical topology of a traditional Ethernet network is a bus The physical topology is often a star The physical topology is often a star

Media Access Control With a bus topology there must be a mechanism to either prevent, or detect and deal with, collisions on the media With a bus topology there must be a mechanism to either prevent, or detect and deal with, collisions on the media CSMA/CD CSMA/CD Full-duplex Ethernet Full-duplex Ethernet

Types of Ethernet 10Base-5 10Base-5 10Base-2 10Base-2 10Base-T 10Base-T 100Base-T 100Base-T 10/100 Ethernet 10/100 Ethernet 1000Base-T 1000Base-T

Switched Ethernet The switch replaces the hub in the network The switch replaces the hub in the network The hub repeats every bit of data out every port The hub repeats every bit of data out every port The switch sends the data out the port which is connected to the message recipient The switch sends the data out the port which is connected to the message recipient The switch uses a forwarding table that contains the Ethernet addresses of the computers connected to each port The switch uses a forwarding table that contains the Ethernet addresses of the computers connected to each port

Wireless Ethernet IEEE IEEE The WEP standard has been completely cracked The WEP standard has been completely cracked Uses CSMA/CA for media control Uses CSMA/CA for media control Subject to the “hidden node” problem Subject to the “hidden node” problem Has VCSM (Virtual Carrier Sense Method) as an option to work around the hidden node problem Has VCSM (Virtual Carrier Sense Method) as an option to work around the hidden node problem

Types of Wireless Ethernet IEEE b IEEE b –DSSS – Allows speeds from 1 – 11 Mbps depending on distance and interference –FHSS – Allows speeds from 1 – 2 Mbps IEEE a IEEE a –The standard is still incomplete –Data rate is likely to be 54 Mbps on first iteration –Actual throughput will likely be ~20Mbps

Other Wireless Technologies Infrared wireless Infrared wireless –Requires line of site or white ceilings and walls with diffused infrared Bluetooth Bluetooth –Slated to become standardized as IEEE –Short range networks referred to as piconets with no more then 8 devices –Uses controlled access media access control –Less then 1Mbps throughput

Reducing Network Demand Placing heavily-used applications or data modules on each client computer Placing heavily-used applications or data modules on each client computer Network segmentation – note this is really increasing supply rather then reducing demand Network segmentation – note this is really increasing supply rather then reducing demand

Chapter 7 Backbone Networks

Backbone Network Components Bridges Bridges –Operating at the data-link layer (MAC address) Routers Routers –Operating at the network layer (IP address) Gateways Gateways –Operating at the transport layer (note that this disagrees with the authors table 7-1)

Backbone Network Components Collapsed backbone Collapsed backbone –Chassis-based –Rack-based VLAN’s VLAN’s –Port-based –MAC-based –IP-based –Application-based

ATM Four key differences between Ethernet and ATM in the backbone Four key differences between Ethernet and ATM in the backbone –53-byte fixed-length cells –No error correction –Virtual Channel addressing as opposed to fixed addresses with the path and circuit numbers –Built in Class-of-Service (CoS) and Quality-of- Service (QoS)

ATM Classes of Service Classes of Service –CBR –VBR-RT –VBR-NRT –ABR –UBR LANE vs. MPOA LANE vs. MPOA SVC vs. PVC SVC vs. PVC

Chapter 8 MAN’s and WAN’s

MAN’s Generally constrained to a city or small region between 3 and 30 miles Generally constrained to a city or small region between 3 and 30 miles Generally deployed via either wireless technology or services leased from a carrier Generally deployed via either wireless technology or services leased from a carrier Moderate levels of regulation Moderate levels of regulation

WAN’s Connecting over potentially great distances Connecting over potentially great distances Generally deployed via circuits leased from Common Carriers Generally deployed via circuits leased from Common Carriers Very heavily regulated within North America and usually even worse oversees Very heavily regulated within North America and usually even worse oversees

Circuit Switched Networks Usually depicted by a cloud with your organizations data traveling with many others across the same physical circuits Usually depicted by a cloud with your organizations data traveling with many others across the same physical circuits POTS POTS ISDN ISDN –BRI –PRI –Broadband

Dedicated Circuit Networks Dedicated circuits or dedicated bandwidth within carrier circuits Dedicated circuits or dedicated bandwidth within carrier circuits Ring Architecture Ring Architecture Star Architecture Star Architecture Mesh Architecture Mesh Architecture

T Carrier Services Based on the 64Kbps channel required for a digitized voice connection Based on the 64Kbps channel required for a digitized voice connection T1 – 24 channels * 64Kbps = Mbps T1 – 24 channels * 64Kbps = Mbps –Control information is included bringing the total circuit bandwidth for a stand-alone T1 to Mbps T3 – 28 T1’s – 28 * 1.544Mbps = Mbps T3 – 28 T1’s – 28 * 1.544Mbps = Mbps –With control information = 44,736Mbps

SONET SONET is a North American standard but the ITU recently adopted the SDH standard set which is nearly identical SONET is a North American standard but the ITU recently adopted the SDH standard set which is nearly identical OC-1 = 51.84Mbps OC-1 = 51.84Mbps OC-3 = 3*OC-1 = Mbps OC-3 = 3*OC-1 = Mbps OC-12 = 12*OC-1 = Mbps OC-12 = 12*OC-1 = Mbps

Packet Switched Networks X.25 – older standard now seldom used in North America X.25 – older standard now seldom used in North America ATM ATM Frame Relay Frame Relay Ethernet/IP Networks Ethernet/IP Networks

Virtual Private Networks Intranet Intranet –Used to connect your organizations office via the Internet Extranet Extranet –In addition to your organizations office you may also include other organizations with which you do business Access Access –Remote access for employees

Chapter 9 The Internet

Internet Structure Internet architecture Internet architecture NAP’s, MAE’s, and ISP’s NAP’s, MAE’s, and ISP’s –POP’s Peering Peering Autonomous systems Autonomous systems

Internet Access Technologies DSL DSL –Digital Subscriber Line –Uses the local-loop –A modem is placed in the home converting the data from the DSL format to Ethernet ADSL ADSL –G.Lite VDSL VDSL

Internet Access Technologies Cable Modems Cable Modems –DOCSIS Shared media means users compete with each other for bandwidth and unscrupulous neighbors could intercept your data Shared media means users compete with each other for bandwidth and unscrupulous neighbors could intercept your data Throughput suffers due to hardware compatibility issues that stem from cable TV infrastructure differences Throughput suffers due to hardware compatibility issues that stem from cable TV infrastructure differences

Wireless Fixed wireless Fixed wireless –Wireless DSL –Satellite Mobile Wireless Mobile Wireless –WAP –WAE

Internet Governance ISOC (Internet SOCiety) ISOC (Internet SOCiety) – IETF (Internet Engineering Task Force) IETF (Internet Engineering Task Force) IESG (Internet Engineering Steering Group) IESG (Internet Engineering Steering Group) –Each IETF working group is chaired by a member of the IESG IAB IAB IRTF IRTF

Internet Domain Name Reg. Internet name and address registration was handled by John Postel until his death in 1998 Internet name and address registration was handled by John Postel until his death in 1998 In 1998 ICANN (Internet Corporation for Assigned Names and Numbers) was formed In 1998 ICANN (Internet Corporation for Assigned Names and Numbers) was formed In 1999 ICANN established the SRS and has now authorized more then 80 companies to issue Internet names and numbers In 1999 ICANN established the SRS and has now authorized more then 80 companies to issue Internet names and numbers

Internet 2 Next Generation Internet Next Generation Internet –vBNS Abilene Abilene CA*net 3 CA*net 3

Chapter 10 Network Security

Why Networks Need Security The average cost to companies for a single security breach is slightly less then $1M The average cost to companies for a single security breach is slightly less then $1M This is a minor cost when compared to the loss of customer confidence This is a minor cost when compared to the loss of customer confidence The text indicates that 24 hours of downtime would cost Bank of America $50M The text indicates that 24 hours of downtime would cost Bank of America $50M

Types of Security Threats Disruptions Disruptions –Minor cable breaks to earthquakes Unauthorized Access Unauthorized Access –More often the work of an employee then an outside hacker

Network Controls Controls are processes or steps to reduce or eliminate threats Controls are processes or steps to reduce or eliminate threats Three types of controls Three types of controls –Controls that prevent threats –Controls that detect threats –Controls that correct threats

LAN Security Although sometimes overlooked a good first step is to ensure that the LAN hardware is physically secure Although sometimes overlooked a good first step is to ensure that the LAN hardware is physically secure Firewalls Firewalls –Packet-level –Application-level NAT (Network Address Translation) NAT (Network Address Translation)

LAN Security Encryption Encryption –Symmetric »DES »Triple DES »AES –Asymmetric (PKI) »PGP (Pretty Good Privacy) »SSL (Secure Sockets Layer) »IPSec (IP Security)

Detecting Unauthorized Access IDS (Intrusion Detection Systems) IDS (Intrusion Detection Systems) –Network-based –Host-based –Application-based Two IDS Techniques Two IDS Techniques –Misuse detection –Anomaly detection

Chapter 11 Network Design

Network Design Process Traditional design process Traditional design process Building Block Design Process Building Block Design Process –Needs analysis –Technology design –Cost assessment Why network projects fail Why network projects fail –Management focus 11-2

Request For Proposal Background information Background information Network requirements Network requirements Service requirements Service requirements Bidding process Bidding process Information required from vendor Information required from vendor

Chapter 12 Network Management

Tasks performed by the network manager Tasks performed by the network manager Five key management tasks Five key management tasks Key network management skills Key network management skills Configuration management Configuration management

Performance & Failure Statistics Availability Availability MTBF MTBF MTTRepair MTTRepair Policy-Based Management Policy-Based Management Service-Level Agreements Service-Level Agreements

Cost Management Sources of cost Sources of cost TCO (Total Cost of Ownership) TCO (Total Cost of Ownership) –$8,000 - $12,000 per device per year? –$1,500 - $3,500 per device per year? (NCO) Five steps to reduce network costs Five steps to reduce network costs

Network Management Tools Three types of network management software Three types of network management software –Device management –System management –Application management SNMP SNMP –MIB –RMON