CNIT 342 Exam 3 Review Questions With Correct Answers

What is SMTP? - Answer - simple mail transfer protocol - delivers mail between hosts - host must always be available - TCP 25 - seven bit ASCII encoding - binary files sent through MIME True/False: Only one mail item is sent to any individual host via SMTP. - Answer True Where is mail spooled in SMTP? - Answer - on hosts True/False: SMTP delivery is real time. - Answer False How long will hosts try to deliver mail before failing? - Answer 72 hours How are users addressed in SMTP? - Answer user@host How are hosts defined in SMTP - Answer - fully-qualified host names () - MX records - forwarding How is DNS aliasing via MX records accomplished? - Answer - mail sent to domain name rather than a fully qualified DNS host name - MTA always looks for MX record first (then looks for A record if no MX record found) - multiple targets can be specified MX 10 ie. resolves to How is email forwarding accomplished? - Answer - one gateway host can be set up as primary focal point for all incoming mail - forwards mail to appropriate host - can be used with DNS aliasing DNS @ to forwards to When mail arrives at a host, what can happen to the mail? - Answer - delivered - forwarded - refused (bounced) What are some SMTP email bounce reasons? - Answer - unknown host (couldn't resolve DNS entry) - host unreachable (mail must time out first) - unknown user (user's mailbox is full) What is an SMTP HELO command? - Answer - connection request from the sending system What is the POP3 protocol? - Answer - post office protocol 3 - extension to SMTP (uses TCP) - used when a user's computer IS NOT always attached to the network - mail cached on server that supports SMTP - remote user connects to mail server and retrieves mail using POP3 - POP3 connections always initiated by the client Which email protocol should be used when a user's computer is NOT always attached to the network? - Answer POP3 Which type of email connections are always initiated by the client? - Answer POP3 What is IMAP? - Answer - similar to POP3 - used to access mail on mail server - mail remains on server - mail server MUST support SMTP to receive email Which email protocol causes mail to remain on the server? - Answer IMAP What is a list server? - Answer - specialized mail server - takes a message sent to a single address and forwards it to a list of addresses - may require significant bandwidth for SMTP traffic - many solutions allow users to manage "accounts" themselves (little administration required) - subscription, unsubscription, changing options - ie. Majordomo, MailMan, Listserv What type of mail server requires little administration? - Answer list server What are the various types of list servers? - Answer - unmoderated - self-moderated - moderated What is the recommended practice in terms of default reply to addresses with a list server? - Answer - do NOT make the default reply-to address be the list itself - leave it as the sender - replies can be sent to the list with the reply to all What are Internet news servers? - Answer - set of interconnected servers arranged in a hierarchy - when message "posted" to one server, it gets copied to all other servers - communications are handled by NNTP (Network News Transfer Protocol) - uses TCP - most groups require a formal creation process - anyone can create an alt.* group What protocol handles Internet newsgroup communication - Answer NNTP (Network News Transfer Protocol) What are some of the primary uses of time in computers? - Answer - time-stamping files - expiration on tickets - calendaring - e-mail - logging - tracing - troubleshooting What is the Julian Calendar? - Answer - 365 days in year - error in leap year calculation What is the Gregorian Calendar? - Answer - fixed leap year calculation When was the calendar changed from the Julian to the Gregorian calendar? - Answer - September 19, 1752 - 11 days skipped to make up for leap years not taken in previous years How is time represented in terms of time zones? - Answer - AM/PM vs military time - time zones vs. UTC/GMT/Zulu - daylight savings time How do UNIX machines represent time? - Answer - system clocks use UTC (ie. 13:00 -5 DST) - keeps time based on seconds since UNIX epoch (00:00:00 January 1, 1970) - will overflow on January 19, 2038 if not fixed How do Windows machines represent time? - Answer - system clocks are based on the local time zone (9:00 AM -5 +1) When was the UNIX Epoch? - Answer 00:00:00 January 1, 1970 What is the real-time BIOS clock? - Answer - keeps time in BIOS (hardware) - keeps time when computer is turned off - notoriously inaccurate How is system time kept? - Answer - kept by a process running in the OS - process depends on processor clock speeds problematic if: - process is over/underclocked - system clock slows to save power - virtual machines are used How is time synchronization accomplished in a non-domain Windows environment? - Answer - no built-in synchronization - default method is to sync to via SNTP How is time synchronization accomplished in a Windows domain environment? - Answer - PDC FSMO role is time server - all domain members synchronize to the PDC Which time protocol do pre-2003 SP1 Windows machines support? - Answer only support SNTP Which time protocol do 2003 SP1 and later Windows machines support? - Answer NTPv3 What is SNTP? - Answer - simple network time protocol - single transaction - sets the time ONCE - can be done repeatedly on a schedule - time can be off between syncs - default for "Internet Time" in Windows What is NTP? - Answer - network time protocol - uses UTC complete with leap seconds (Marzullo's Algorithm; takes into account transmission duration for time data) - keeps clock CONSTANTLY correct - requires client to adjust its internal clock to match the reference time (slew, drift [drift file]) - as time process "tunes" itself, reference clock is constantly checked) - when time process is keeping good time, duration between checks is increased Which time protocol keeps client system clocks constantly correct? - Answer NTP