z/VM: TCP/IP User's Guide - z/VM - IBM

the transport layer. FTP transfers files as either ASCII characters or as binary data.
ASCII characters are used to transfer files that contain only text characters.
FTP provides functions, such as listing remote directories, changing the current
remote directory, creating and removing remote directories, and transferring one or
more files in a single request. Security is handled by passing user and account
passwords to the foreign hosts.
For more information about FTP, see RFC 959.
Trivial File Transfer Protocol (TFTP)
Trivial File Transfer Protocol (TFTP) is designed only to read and write files to and
from a foreign host. TFTP is built on the services of UDP in the transport layer.
TFTP allows you to limit drive and directory access.
TFTP, like FTP, can transfer files as either ASCII characters or as binary data.
However, unlike FTP, TFTP cannot be used to list or change directories at a foreign
host, and it has no provisions for user authentication.
For more information about TFTP, see RFC 783.
Internet Message Access Protocol (IMAP)
The Internet Message Access Protocol (IMAP) is a mail protocol with both client
(sender) and server (receiver) functions.
IMAP provides the processing that allows a client to access electronic mail that is
kept in an IMAP Mailstore server. It permits a ″client″ email program to access
remote message folders called ″mailboxes″, as if they were local.
For more information about IMAP, see RFC 2060.
Simple Mail Transfer Protocol (SMTP)
The Simple Mail Transfer Protocol (SMTP) is an electronic mail protocol with both
client (sender) and server (receiver) functions.
SMTP is implemented with the CMS NOTE and CMS SENDFILE EXECs in a VM
environment. You do not interface directly with SMTP. Instead, electronic mail
software is used to create mail, which in turn uses SMTP to send the mail to its
destination.
For more information about SMTP, see RFCs 821, 822, 974, 1413, and 1440.
Domain Name System (DNS)
The Domain Name System (DNS) uses a hierarchical-naming system for naming
hosts. Each host name is composed of domain labels separated by periods. Local
network administrators have the authority to name local domains within an
internet. Each label represents an increasingly higher domain level within an
internet. The fully qualified domain name of a host connected to one of the larger
internets generally has one or more subdomains.
For example:
host.subdomain.subdomain.rootdomain
or
host.subdomain.rootdomain
TCP/IP Protocols and Functions
For more information about the Domain Name System, see RFCs 1034 and 1035.
Chapter 1. Introducing Computer Networks and Protocols 7