1. Application Protocols SMTP: Simple Mail Transport Protocol HTTP: Hyper Text Transport Protocol HTTPS: Hyper Text Transport SSL (Secure) SNMP: Simple Network Management Protocol FTP: File Transfer Protocol Telnet: Interactive login SSH: Secure Shell telnet DNS: Domain Name Service

2. IP header Source and Destination IP addresses Type of Service –Selects delivery speeds vs. accuracy Protocol (TCP,ICMP, UDP) Time to Live (Router hops) Identification and Fragment offset –Reassembly of a fragmented datagram

3. VersionLengType of SvcTotal Length IdentificationFlags Frag Offset Time to Live ProtocolHeader Checksum IP Header Source Address Destination Address TCP Header then your data...

4. TCP fields Ports (service identifiers) Sequence numbers Acknowledgement numbers Windowing –More retries (less acks) smaller packets –Less retries (more good data) larger packets

5. Source PortDestination Port Sequence Number Acknowledgement Number Data Offset Reserved Flags Window Checksum Urgent Pointer Your Data… next 500 octets TCP Header

6. Services RFC’s (Requests for Comments) /etc/services or multinet:services.master_server lists service name and port number Common (well known) ports: –FTP 21 –TELNET 23 –SSH 22 –SMTP 25 –HTTP 80 –NTP 123 –Finger 79

7. TCP Data Flow Computer 129.123.7.33, 129.123.1.86 Port info:1234, 23 129.123.1.86 1234 Returning Port Listens on port 23

8. UDP Data Flow Computer 129.123.7.33, 129.123.1.86 Port info:1234, 123 129.123.1.86 Reply 1 Port 123 Reply 2 Port 123

9. TCP, UDP, ICMP TCP (Transmission Control Protocol) –Datagrams –Connection Oriented –End to End error checking –Source Port, Destination Port Sockets, Well Known Ports –HTTP, SMTP, TELNET,FTP

10. UDP (user datagram protocol) Connectionless One Way Fast, Simple No guarantee of delivery NFS, DNS, DHCP, NTP, TALK

11. ICMP (Internet control message protocol) Error Messages Intended for the TCP/IP software itself PING (host unreachable messages) Simple Headers

12. FTP File Transfer Protocol (TCP) –User authentication –Anonymous GET/PUT/DEL/CWD Binary/Ascii

13. FTP Example requires 2 ports telnet ftp.remotesite.com 21 –220 ftp.remotesite.com FTP server ready –user anonymous –331 password required for anonymous –password user@cc.usu.edu –230 user anonymous logged in –PORT 1200

14. FTP Example cont. PORT 129,123,7,55,4,76 200 PORT command successful pwd 257 “/export/guest/bobw” is current directory RETR./.login 150 ASCII data connection for./.login(129.123.7.55,1100)(795 bytes) QUIT

15. HTTP Application HTTP is a pull protocol, the user pulls information from a remote site. Protocol consists of GET and POST commands to transfer data. Persistent vs. Non-Persistent connections

16. Non-Persistent Connections TCP connections are opened and closed for each request. Allows for parallel transfer of objects.

17. Persistent Connections TCP connection left open until requested to disconnect or times out. Takes advantage of pipelining to improve transfer rates.

18. Proxy Servers HTTP uses cached files to speed up transfers Proxy Server is a LAN accessible cache Proxy allows for reduced load on the internet connection Proxy Servers allow NAT (Network Address Translation) systems to protect internal networks.

19. MIME Types/Encoding Multipurpose Internet Mail Extensions Handles Non-ASCII data in an ASCII transfer medium. Imbeds the data stream into the email message

20. Simple Mail Transfer Protocol The protocol is very simple SMTP is a push protocol, information is pushed to a remote sitre Uses port 25 All files are ascii text Syntax: user@host.domain user@host.domain Mail relay: user%host1@host2.domainuser%host1@host2.domain Mail Exchange (MX) –Allows mail server redirection

21. SMTP Example 1> telnet red.rutgers.edu 25 2> 220 RED.RUTGERS.EDU SMTP Service at 15 Apr 98 10:11:18 EDT 1> HELO pc15.logan.com 2> 250 RED.RUTGERS.EDU - Hello, PC15.LOGAN.COM 1> MAIL From: 2> 250 MAIL accepted 1> RCPT To: 2> 250 Recipient accepted 1> DATA 2> 354 Start Mail input; end with. 1> Date: Sat, 22 Mar 1998 13:26:31 MST 1> From: student11@pc15.logan.com 1>Subject: Meeting tomorrow

22. SMTP Example cont. 1> The meeting is TOMORROW at 3:00 PM! 1> 1>. 2> 250 OK 1> QUIT 2> 221 RED.RUTGERS.EDU Service closing transmission channel

23. POP3 Post office protocol Mail access client Uses port 110 Messages are downloaded to client but can be stored on server. Does not easily allow multiple clients

24. POP3 Example telnet cc.usu.edu 110 +OK POP3D(*) Server PMDFV6.1.2 at Wed, 8 Sep 2004 10:49:30 MdT 01LEMEHLU2FMBOTAK2@grumpy.usu.edu 01LEMEHLU2FMBOTAK2@grumpy.usu.edu user bobw +OK password please pass areukidding +OK Mailbox open, 335 messages list (List of messages) 1 4355 2 106 3 445567 retr 2 (dumps message, ends with a.) quit +OK bye

25. IMAP Internet Mail Access Protocol Improved POP3 Automatically assigns folders Leaves mail on server Only transfers as much as needed per message (headers, subject only on list)

26. DNS Domain Name Services What’s in a name? Distributed hierarchical architecture Caches and times DNS entries for speed www.internic.net (root server)www.internic.net Top Level Domain Servers Authoritative Local Nameservers –thingy, watzit, doober

27. DNS Configuration File ; ; Hosts file for domain flibble.orac.net.au. ; ;name ttl class type data ; ; Source of authority @ IN SOA solaris.flibble.orac.net.au. root.solaris.flibble.orac.net.au. ( 2000050201 ; Serial 10800 ; Refresh - 3 hours 3600 ; Retry - 1 hour 432000 ; Expire - 1 week 86400) ; Minimum - 1 day IN NS solaris.flibble.orac.net.au.

28. More Config ; ; Machines for the flibble.orac.net.au domain ; ;name ttl class type data localhost IN A 127.0.0.1 solaris IN A 10.5.3.1 win95 IN A 10.5.3.21 linux IN A 10.5.3.22 ; ; Aliases ; mail IN CNAME solaris www IN CNAME solaris

29. More config ; ; Domain mailing addresses ; flibble.orac.net.au. IN MX 10 solaris.flibble.orac.net.au. flibble.orac.net.au. IN A 10.5.3.1

30. DNS Resolution Want cc.usu.edu Top Level Domain Server (resolve.edu) thingy.usu.edu resolve usu.edu resolve cc.usu.edu homeuser.aol.com

31. USU DNS Handled by Network and Computing Services thingy.usu.edu webpage for registrations and lookups