1 / 29

Selected TCP/IP Applications

Selected TCP/IP Applications. Remote Terminal Emulation (TELNET) File Transfer Protocol (FTP) Trivial File Transfer Protocol (TFTP) Simple Mail Transfer Protocol (SMTP) Post Office Protocol (POP) Domain Name Service (DNS) Simple Network Management Protocol (SNMP). TELNET. TELNET server.

ina
Download Presentation

Selected TCP/IP Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Selected TCP/IP Applications • Remote Terminal Emulation (TELNET) • File Transfer Protocol (FTP) • Trivial File Transfer Protocol (TFTP) • Simple Mail Transfer Protocol (SMTP) • Post Office Protocol (POP) • Domain Name Service (DNS) • Simple Network Management Protocol (SNMP)

  2. TELNET TELNET server TELNET server Host TELNET client

  3. TELNET Options • Each side of the connection requests or tells its partner the options it wants or can do. • Options are formatted in: • WILL or WON’T <option> • DO or DON’T <option> • Negotiates options such that symmetry can be set up between two stations. • Options include: • Ability to echo • Terminal type • Setting line mode so that groups of characters can be sent

  4. File Transfer Protocol (FTP) Host Storage Client

  5. FTP Commands • open–creates a connection between two hosts. • close–closes a connection between two hosts. • bye–ends the FTP session. • binary–indicate that the file is binary data. • get–get the remote file. • mget–wildcard to get multiple files. • put - puts a file to the remote resource. • mput - wildcard to put multiple files. • cd - change directory on the remote device. • dir - get a directory listing on the remote device. • ldir - get a local directory. • hash - display hash marks during the transfer.

  6. FTP Example 99,760 bits per second

  7. Trivial File Transfer Program (TFTP) • A simplex file transfer program. • Uses UDP. • Transfers 512 bytes at a time. • Transfers one segment at a time. • Acknowledged by the application. • Any datagram less than 512 bytes indicates the last datagram in the transfer. • Popular for network booting of devices.

  8. Domain Name Service (DNS) (1) Name Query “Sun_Server” TELNET Sun_server (2) Query Response “198.1.1.1” (3) Connection • Provides a naming service for TCP/IP. • Provides many functions related to IP addresses and names • Three components • A name server, a name resolver, and a database Name Server 110001 101010 198.1.1.1 198.1.1.2 Database containing the mapping for Sun_Server 198.1.1.1 DNS Resolver

  9. DNS Structure • Hierarchical in structure. • Each level provides further definition. • Each branch is called a level (63 characters in length). • Internet Registry provides uniqueness in names. • A single domain is assigned and may be further defined by the local site.

  10. DNS Components • Domain Name Space and resource records • Name servers • Resolvers

  11. Domain Structure Root Server com edu com gov mil net .firm .arts .nom .rec .info .web .store The extra top-level domains (TLDs) that are shown as the bottom set of boxes are proposed, they are shown here as examples, and as of this writing have not been adopted.

  12. Name Servers Upstream name server for other domains graydon.com vax. mail. host. Database file marketing zone .marketing.graydon.com vax 192.32.1.15 mail MX vax host 192.32.1.17 .engineering.graydon.com engineering zone hr zone .hr.graydon.com manufacturing zone .manufacturing.graydon.com

  13. Name Servers (continued) Query “labhost.bnr.ca.us” Root server Referral to us server Query “labhost.bnr.ca.us” Query “labhost.bnr.ca.us” .us server Referral to ca.us server Query “labhost.bnr.ca.us” Name Server .ca.us server IP address of “labhost.bnr.ca.us” Referral to bnr.ca.us server Query “labhost.bnr.ca.us” bnr.ca.us server IP address of “labhost.bnr.ca.us”

  14. Query Functions Types Query “Host” Response “Can’t find it” • Two types of queries: recursive and iterative. • Recursion means that the server must find the answer or return an error code • The resolver is an example of a recursive query • Iterative allows a server to return the best-known information • Servers are examples of both recursive and iterative Root server Query “Host.jj.com” jj.com Name Server Response “IP Address” host.jj.com jj.com

  15. Example DNS Database • Records in the database include: • A–host’s IP address • PTR–host’s domain name, host identified by its IP address • CNAME–host’s canonical name, host identified by an alias domain name • MX–host’s or domain’s mail exchanger • NS–host’s or domain’s name server(s) • SOA–Indicates authority for the domain • TXT–generic text record • SRV–service location record • RP–text name of the person responsible for the domain DNS

  16. SOA Record Name server for domain Authoritative for domain Naugle.com IN SOA ns1.Naugle.com. Matt.NT1Server.Naugle.com. ( 1567 ;Serial 18000 ;Refresh after five hours 3600 ;Retry after 1 hour 604800 ;Expire after one week 86400) ;Minimum TTL of 1 day Information for the secondary server Person responsible

  17. Name Server Records • Naugle.com. IN NS ns0.Naugle.com. • Naugle.com. IN NS ns1.Naugle.com. • Naugle.com. IN NS ns2.Naugle.com. • Naugle.com. IN NS ns3.Naugle.com. • Naugle.com. IN NS ns4.Naugle.com.

  18. Address Records LocalHost.Naugle.com. IN A 127.0.0.1 DatabaseServer.Naugle.com. IN A 128.1.1.1 HRServer.Naugle.com. IN A 128.1.15.1 EngServer.Naugle.com. IN A 128.1.59.150 NS0.Naugle.com. IN A 128.1.1.2 NS1.Naugle.com. IN A 128.1.15.2 NS2.Naugle.com. IN A 128.1.16.190 NS3.Naugle.com. IN A 128.1.59.100 NS4.Naugle.com. IN A 128.1.59.101 ;Aliases NT1.Naugle.com. IN CNAME DBServer.Naugle.com NT2.Naugle.com. IN CNAME HRServer.Naugle.com.

  19. Mail Exchange Records (MX) engineering.naugle.com. IN MX 5 mail.naugle.com. engineering.naugle.com. IN MX 5 mail1.naugle.com. engineering.naugle.com. IN MX 10 mail2.naugle.com.

  20. Playing with the Database • nslookup <domain name> <IP Address> • Go to Web site: ://ds/internic.net/cool/dns.html • Use this to see if a domain name is already assigned!!

  21. WHOIS Command • Enables you to get more information on domain names, networks, etc., on the Web. • ://ds.internic.net/cgi-bin/whois. • “whois ascend.com” (without the quotes). • Details Ascend.com domain such as: • Administrative contact (who to call) • Domain servers • Can determine IP address blocks. • WHOIS net 192.1 • BBN Corporation NETBLK-BBN-CNETBLK BBN-NCETBLK 192.1.0.0-192.1.255.255

  22. More DNS Information • 2136 PS: P. Vixie, S. Thomson, Y. Rekhter, J. Bound, “Dynamic Updates in the Domain Name System (DNS UPDATE)”, 04/21/97 (26 pages). • 2137 PS: D. Eastlake, “Secure Domain Name System Dynamic Update,” 04/21/97 (11 pages) (.txt format). • 1996 PS: P. Vixie, “A Mechanism for Prompt Notification of Zone Changes (DNS NOTIFY),” 08/28/96 (7 pages) (.txt format). • 1995 PS: M. Ohta, “Incremental Zone Transfer in DNS”, 08/28/96 (8 pages) (.txt format). • www.isc.org • DNS and BIND • Book by Paul Albitz and Cricket Liu • ISBN 1-56592-236-0

  23. Simple Mail Transfer Protocol (SMTP) • Today known as Electronic Mail, or email. • RFCs 821, 822, 974. • Email still cannot transport packages and other items. • Email is very fast and guarantees delivery. • Three protocols are used for today’s email. • SMTP–operates over TCP • POP–operates over TCP • DNS–operates over UDP • SMTP allows for the sending/receiving of email. • POP allows us to intermittently retrieve email. • DNS makes it simple.

  24. SMTP Functions • A message is created, properly addressed, and transmitted using SMTP sender, which transmits it to an SMTP receiver, which stores the file. • Address has the format of: • local-part@domain-name • Example: matt@naugle.com • Mail service record in DNS: • naugle.com IN MX 10 NT1mail_server.eng.naugle.com • SMTP was set up to handle only text. • Based on the history of the protocol • Email applications convert using a variety of protocols like MIME (Multipurpose Internet Mail Extensions).

  25. SMTP Flow SMTP sender SMTP receiver Accept connection send READY TCP Call on port 25 SEND MAIL command Send OK Identify recipients to receiver Send OKs for recipients; otherwise, reject Send mail Send OK at end Quit Response to Quit

  26. DNS Interaction for Mail DNS lookup for MX record for ibm.com Sender SMTP Internet mail.ibm.com Receiver SMTP

  27. Post Office Protocol (POP) • SMTP is set up to send and receive mail by hosts that are up full time. • No rules for those hosts that are intermittent on the LAN • POP emulates you as a host on the network. • It receives SMTP mail for you to retrieve later • POP accounts are set up for you by an ISP or your company. • POP retrieves your mail and downloads it to your personal computer when you sign on to your POP account.

  28. POP Operation POP Server POP Client TCP port 110 connection attempt “POP3 server ready” reply Wait for authentication Send authentication Process authentication and if okay, enter transaction state Lock mailbox for user. Assign messages numbers Send messages Delete (possibly) messages Retrieve all messages Send QUIT command Session closed Read messages locally Quit received Perform update on mailbox

  29. SMTP, DNS, and POP Topology Your ISP Retrieve mail Your PC POP Server mnaugle user1 user2 Send mail DNS SMTP POP3/SMTP root DNS Internet Remote ISP DNS SMTP send mail Joe’s PC POP Server joe Retrieve mail

More Related