1. Network Services Networking for Home & Small Business

2. Client-Server Server –Host running an application that provides info or services to a client Web Server Email Server File Server Browser- widely used client software

3. Client-Server Web Site domain names to IP address translation Remote login to device to control it Send/Receive email Assigns IP addresses Web SiteFile Transfer

4. 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

5. 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

6. Roles of Protocols in Communication A web server & client use specific protocols and standards in exchanging info to ensure that the messages are received & understood. HTTP –An Application protocol –Rules of how a web server/client interact –Relies on other protocols to deliver the messages TCP –Transmission Control Protocol –A Transport protocol –Manages the individual conversations –Formats messages –Acknowledgements, retransmissions

7. Roles of Protocols in Communication IP –Internet protocol –Assigns addresses, encapsulates message into packets

8. Roles of Protocols in Communication Network Access Protocols –Data Link Management –Takes packets from IP and formats them into frames for your network –Assigns the MAC address so it can be sent over the network Physical Network Transmission –How the bits go on media Electricity, light, radio…ones & zeros

9. TCP & UDP Transport Protocols The IP protocol uses these transport protocols to enable hosts to communicate and transfer data.

10. Transmission Control Protocol Used when an application requires an acknowledgement –Like a registered letter in the mail Breaks messages into small numbered segments & ready to become packets 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 6.1.3.2 Example

11. User Datagram Protocol Used for faster transmissions “Best effort delivery” No ACK No retransmission –Standard postal letter Used for streaming audio or video, Internet radio, VoIP

12. 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.

13. Review

14. Port Numbers & Communication When message is delivered, port # assigned Used to keep track of conversations and destination services requested Each message sent, has a source & destination port number

15. Port Numbers, Communication & Sockets source & destination IP source & destination port numberThe 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

16. Port Numbers Destination- tells about service requested –80- HTTP –25- SMTP –53- DNS –21- FTP –23- Telnet Source Port –Random –Allows multiple conversations

17. 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

18. Lab DNS Lab 6.2.1.3

19. Review What does www.gcit.org represent?www.gcit.org –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

20. 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

21. Web Communication You want www.cisco.comwww.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

22. Web Clients & Servers HTTP is not secure Secure HTTP (https:) is port 443

23. 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

24. FTP Up/downloading of files, music, web site

25. Email Email server receives & stores emails You email client allows access to view messages user@company.domain Protocols used in email include SMTP, POP3, IMAP4

26. Email Protocols- SMTP SMTP (25) –Used to send email from client to server –Email server to email server

27. Email Protocols- POP3 POP3 (110) –Used to send client messages & deleted from storage on the server Mail on server until collected from client

28. Email Protocols- IMAP4 IMAP4 (143) –Like POP3, but it keeps messages on server until user deleted them

29. Configuring Email

30. IM Protocols: Clients & Servers Real-time communication Each IM service may use different protocols & destination ports –So you must have compatible IM software

31. Voice Protocols: Clients & Servers VoIP Can call similar clients –Calls to landlines need public phone network

32. More About Port Numbers- 6.2.7.2 1-65,535 Well-known ports –1- 1023 –Common applications Registered ports –1024- 49,151 –Used for specific applications like IM –Source/dest ports Private ports –49,152 & above –For source ports

33. 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

34. 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

35. TCP/IP Model

36. 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

37. Receiving a Message 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

38. OSI Model Primary model for protocol development Unlike TCP/IP model, this is for all protocols

39. Activity 192.168.5.101 80 or TCP or UDP 01-5A-FF-65-80-DC 1100101101000010 DHCP or POP3 or HTTP

40. Activity Complete 6.3.3.4 6.3.3.5

41. Network Services Networking for Home & Small Business