fundamentals of networking
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Fundamentals of Networking. Discovery 1, Chapter 6 Network Services. Objectives. Compare and contrast clients and servers, and their interaction over the network. Describe the type of interactions of Internet applications. Describe the purpose of a layered model. - PowerPoint PPT PresentationTRANSCRIPT
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Fundamentals of NetworkingDiscovery 1, Chapter 6Network Services
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Objectives•Compare and contrast clients and servers, and their
interaction over the network.
•Describe the type of interactions of Internet applications.
•Describe the purpose of a layered model.
• Illustrate the interaction on various protocols.
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Introduction•Everyday we communicate across the Internet▫What kinds of activities?
•What’s in common with all of these?▫Servers
•All these interactions use standards & protocols
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Client-Server•Web Page Request▫Client has web client
software Browser- widely used
client software▫Server
Host running an application that provides info or services to a client
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Types of Servers
Web Site domain names to IP address translation
Remote login to device to control it
Send/Receive email
Assigns IP addresses
Web Site File Transfer
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Activity•Complete 6.1.1.4▫Match the service to the client’s request
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Standardized Communication•Different computers & operating systems across the
Internet▫Communication not possible if they didn’t share a
protocol
•Phone call China to US▫We have connectivity▫A Chinese sales person couldn’t be understood by an
English speaking person▫That’s why there’s protocols (rules) to follow
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Licklider•DoD•Saw the need for
networked computers•3 bidders w/ different
systems▫They couldn’t communicate
with each other▫Came up with the idea of
ARPAnet, which later became the Internet
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Client Server Interaction•A web server & client use specific protocols and
standards in exchanging info to ensure that the messages are received & understood.
•Application, transport, Internetwork and network access protocols
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Client Server Interaction•Application Protocols•HTTP▫Rules for how browser & web
server interact
•You request web page•Another protocol delivers it
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Client Server Interaction•Transport Protocols•TCP▫Manages the conversations/packet exchange▫Splits message into segments▫Flow control & acknowledgments between the hosts▫Retransmission
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Client Server Interaction• Internetwork Protocols• IP▫Assigns IP addresses▫Encapsulate into packets for routing
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Client Server Interaction•Network Access Protocols▫Get on the Ethernet cable!!!
•Data Link Management▫Takes packets & encaps them into frames▫MAC addresses are attached here
•Physical Transmission▫How bits go on media (wired, wireless)
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Overview
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Review•Which server…▫Translates names to IP addresses?▫Used for remote login?▫Assigns IP addresses?
•Which protocol…▫Splits data into segments?▫Controls flow of data?▫Acknowledges receipt of data?▫Requests retransmission if a piece is missing?
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End of Day One
Review•Which protocol adds the IP addresses?
•Which category of protocols encapsulates packets into frames?
•Which protocol is for the rules of how a browser & web server communicate?
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TCP & UDP Transport Protocols• Each protocol does its’ own
job▫ IP addresses & routes data
Doesn’t say how it is transported
• Different applications use different protocols for transport of the data▫ How data is sent/exchanged
• TCP or UDP
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Transmission Control Protocol•Used when an application requires an
acknowledgement▫ Like a registered letter in the mail
•Breaks messages into small numbered segments▫ If sender doesn’t get an ACK of message received, it
retransmits ▫Only portion lost is resent
•On receiving host, TCP reassembles data•FTP & HTTP are examples of protocols using TCP• Look at 6.1.3.2 Example
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User Datagram Protocol•Used for faster transmissions• “Best effort delivery” ▫Standard postal letter
•No ACK or retransmission•Used for streaming audio or video, Internet radio,
VoIP
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UDP & Internet Radio• If some of the message is
lost, it is not retransmitted. ▫ You might hear a slight
break in the sound. • If TCP were used and the
lost packets were resent, the transmission would pause to receive them and the disruption would be more noticeable.
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Compare TCP & UDP• Let’s do this together
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Review
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Keep Track of Conversations•All the conversations need to be tracked▫Port Number▫A # in each segment▫Helps identify what service the message is for
Web request, email, DHCP, etc.
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Port Numbers & Communication•Each message sent, has a source & destination port
number•Source Port- randomly generated▫Placed into the segment
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Port Numbers, Communication & Sockets
•The combo of the source & destination IP AND the source & destination port number is known as a socket. ▫Used to identify the server and service being requested
by the client. ▫Thousands of requests per day are tracked by this
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Destination Port Numbers•Destination- tells about service requested▫80- HTTP▫25- SMTP▫53- DNS▫21- FTP▫23- Telnet
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Application Protocols
& Services
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Domain Name Service•Server with table of IP &
host names•Request sent to port 53
(DNS)▫DNS server looks in table
to translate it▫ If there, it lets client know▫ If not there, forwards to
another DNS server If no learn, time out
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Lab•DNS Lab▫Lab 6.2.1.3 Handout▫Use nslookup
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Review•What does www.gcit.org represent?▫An IP address
•Which server would translate that name to an IP address?▫DNS server
•Which server would assign IP addresses?▫DHCP server
•Which Application protocol does FTP use?▫TCP
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Review•Why would an application use UDP?▫No disruption if dropped packets (fast)▫Slight interruption, but it keeps going
•Which protocol is used for web sites?▫HTTP
•Which port # is…▫FTP
21▫HTTP
80
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Web Communication•You want www.cisco.com•DNS gets you the IP address of it•Your browser uses that IP & port 80 to request the
web page•Socket connection made with server•Web page comes back to your browser encoded in
HTML
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Web Clients & Servers•HTTP is not secure•Secure HTTP (https:) is port 443
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Lab•Packet Tracer 6.2.2.2 together
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FTP Clients & Servers•Transfer files from host to host•Built in to OS & browsers•Also GUI based software available
•Client/Server•Uses TCP•Request to server on port 21•Port 20 to send files to client
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FTP•Up/downloading of files, music, web site
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Email•Email server receives & stores emails•You email client allows access to view messages•[email protected] •Protocols used in email include SMTP, POP3, IMAP4
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Email Protocols- SMTP•SMTP (25)▫Used to send email from client to server▫Email server to email server
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Email Protocols- POP3•POP3 (110)▫Used to send client messages & deleted from storage
on the server Mail on server until collected from client
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Email Protocols- IMAP4• IMAP4 (143)▫Like POP3, but it keeps messages on server until user
deleted them
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Email Communication & Protocols
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Configuring Email Example
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Review
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IM Protocols: Clients & Servers•Real-time communication•Each IM service may use different protocols &
destination ports▫So you must have compatible IM software
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Voice Protocols: Clients & Servers•VoIP•Can call similar clients▫Calls to landlines need public phone network
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More About Port Numbers- 6.2.7.2•1-65,535•Well-known ports▫1- 1023▫Common applications
•Registered ports▫1024- 49,151▫Can be source or destination ports▫Used for specific applications like IM
•Private ports▫49,152 & above ▫For source ports
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Port # Review•6.2.7.2
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Review•Which email service protocol…▫Is used to send mail to server?
SMTP▫Is used to get mail from the server & keep it there until
deleted? IMAP4
▫Is used to communicate from email server to email server? SMTP
▫Is used to get mail from the server & delete it? POP3
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Layered Model &
Protocols
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Protocol Interaction•They interact with each other▫Protocol Stack
•Some protocols focus on content of message
•Others focus on moving the data
•Protocols visualized in layers
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TCP/IP Model
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Sending a Message•Web Server to client (you)▫Application data broken into TCP segments
Each segment has a header w/ source & dest ports▫Segment encapsulates HTTP & HTML data▫Encapsulates into a packet w/ IP header
IP header has source & dest IP addresses▫IP Packet sent to Ethernet protocol
Encapsulates into frame header & trailer Source & destination MAC AND error checking
▫Bits encoded onto the media
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Sending- 6.3.2.1
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Receiving a Message- 6.3.2.2• Last process in reverse▫Bits received by NIC & decoded
Destination MAC recognized▫Ethernet header & trailer removed
Source & dest MAC removed▫IP header removed
Source & dest IP removed▫TCP header removed
Source & dest ports removed▫Web page data passed to HTTP & browser▫TCP segment received, reassembled, & page displays
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TCP/IP Model Match
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OSI Model•Primary model for
protocol development•Unlike TCP/IP model,
this is for all protocols
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Viewing OSI in Packet Tracer
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Activity- 6.3.3.3•192.168.5.101
•80 or TCP or UDP
•01-5A-FF-65-80-DC
•1100101101000010
•DHCP or POP3 or HTTP
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Activity•Handout 6.3.3.4•Packet Tracer 6.3.3.5
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Review 1- 9 Questions
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Advanced Review
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Fundamentals of NetworkingDiscovery 1, Chapter 6Network Services