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Management Information Systems

Notes IGMP queries to the all nodes group periodically to see whether any group members exists on
their subnetworks. When it receives no response after a number of queries, the router assumes
that there is not any group member on the network. IGMP messages are of 2 types. They are
Host Membership Query and Host Membership Report. Host membership query multicast
routers send Host Membership Query messages to find out those nodes which have members on
their attached local networks. The Host membership report node responds to a Query by
generating Host Membership Reports reporting each host group to which they belong on the
network interface from which the Query was received.

SMTP

Electronic mail (E-mail) is considered the most widely used TCP/IP application. The Internet
mail protocols enable a client machine to exchange mail and message between TCP/IP hosts.
Three standard protocols are applied to provide such mail application. The SMTP is one of them.
The three standards are given below:
1. SMTP: It is a standard for exchange of mail between two computers (STD 10/RFC 821),
which specifies the protocol used to send mail between TCP/IP hosts.

2. Mail: It is a standard (STD 11) defining the format of the mail messages, syntax of mail
header fields, a set of header fields and their interpretation and about a set of document
types other than plain text ASCII to be used in the mail body.
3. DNS-MX: It is a standard for the routing of mail using the Domain Name System (RFC 974).
SMTP, an application layer protocol, is used to send e-mail messages across the Internet. It
utilizes TCP as the transport protocol to send email to a destination mail exchanger, referred as
mail server. A client machine sends email to a mail exchanger or an email is sent from mail
exchanger to another mail exchanger. E-mail transmitted using SMTP is normally transmitted
from one mail exchanger to another directly. E-mail was never designed to be instantaneous but
it appears so often.
Mail Exchangers are nothing but the software application programs to support the SMTP protocol.
Mail Exchangers such as sendmail or Microsoft Exchange wait for IP datagrams that arrive on
the network interface with a TCP port number of 25. When a message is arrived, the mail
exchanger checks to find out if it is for one of its users and accordingly move the mail to the
user’s mailbox. The data sent using SMTP is 7-bit ASCII data, with the high-order bit cleared to
zero is found adequate in most instances for the transmission of English text messages but is
inadequate for non-English text or non-textual data. To overcome these limitations, Multipurpose
Internet Mail Extensions (MIME) defines a mechanism for encoding text and binary data as
7-bit ASCII within the mail envelope and SMTP Service Extensions specifies a mechanism to
extend the capabilities of SMTP beyond the limitations.

Self Assessment

Fill in the blanks:
15. It is the .............................. that assists the browser to link with a Website.
16. .............................. is a file server access protocol that enables a user to transfer files between
two hosts across the network or Internet using TCP.
17. The .............................. enables application programs to have direct access to a datagram
delivery service like the delivery service that IP provides.

18. .............................. , an application layer protocol, is used to send e-mail messages across
the Internet.

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