TCP IP Illustrated

Hinfo sun host t hinfo sun suntucnoaoedu hinfo sun 425

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: s%20and%20Settings/bigini/Docu.../homenet2run/tcpip/tcp-ip-illustrated/dns_the.htm (12 of 18) [12/09/2001 14.47.06] Chapter 14. DNS: The Domain Name System Host information: two arbitrary character strings specifying the CPU and operating system. Not all sites provide HINFO records for all their systems, and the information provided may not be up to date. HINFO sun % host -t hinfo sun HINFO Sun-4/25 Sun4.1.3 Mail exchange records, which are used in the following scenarios: (1) A site that is not connected to the Internet can get an Internet-connected site to be its mail exchanger. The two sites then work out an alternati ve way to exchange any mail that arrives, often using the UUCP protocol. (2) MX records provide a way to deliver mail to an alternative host when the destination host is not available. (3) MX records allow organizations to provide virtual hosts that one can send mail to, such as, even if a host with that name doesn't exist. (4) Organizations with firewall gateways can use MX records to limit connectivity to internal systems. Many sites that are not connected to the Internet have a UUCP link with an Internet connected site such as UUNET. MX records are then provided so that electronic mail can be sent to the site using the standard [email protected] notation. For example, a fictitious domain might have the following MX records: sun % host -t mx MX relayl.UU.NET MX relay2.UH.NET MX records are used by mailers on hosts connected to the Internet. In this example the other mailers are told "if you have mail to send to [email protected], send the mail to or" MX MX records have 16-bit integers assigned to them, called preference values. If multiple MX records exist for a destination, they're used in order, starting with the smallest preference value. Another example of MX records handles the case when a host is down or unavailable. In that case the mailer uses the MX r...
View Full Document

This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

Ask a homework question - tutors are online