Research

SNMP

What is SNMP?

Simple Network Management Protocol (SNMP) is an Internet standard protocol for managing devices remotely and locally on IP network like routers, switch, servers, workstation etc. It is an application level protocol designed for application layer.

SNMP Versions

Two major versions:

1. SNMPv1 is a recommended standard
2. SNMPv2: 2.1 SNMPv2u - SNMPv2 with user-based security 2.2 SNMPv2*- SNMPv2 with user-based security and additional features 2.3 SNMPv2c- SNMPv2 without security
3. SNMPv3: Started from SNMPv1 addressing security

How SNMP works?

SNMP Architecture: Manager and Agent

1. A manager checks an agent by requesting information that reflects the behavior of the agent
2. A manager forces an agent to perform a task by resetting values in the agent database.
3. An agent contributes to management process by warning the manager of an unusual situation through traps

Agent will receives request on UDP port no. 161 and manager will send request on UDP port no. Manager receives notifications from agent on port no. 162 that called trap event.

SNMP Components

Management information base (MIB): SNMP protocol provide information about devices and that variables information is provided by management information base(MIB). It is collection of objects and their types in hierarchical tree format. Structure of management information (SMI): SMI defines rule for naming objects, defining object types and showing how to encode objects and data.

SMTP

What is SMTP?

Simple Mail Transfer Protocol is a protocol that allows to send email from email client to mail server. SMTP uses domain name in an email address to locate the recipients email server where the email remains until the recipients receive it. It is a part of TCP/IP protocol suit. It defines the message transfer agent (MTA) and message format. Originally SMTP sends only text but MIME and other encoding enable executable program and multimedia file to attach to transported e-mail. SMTP uses TCP port 25

Operation

• When an SMTP client has a message to transmit, it establishes a two- way transmission channel to an SMTP server. The responsibility of an SMTP client is to transfer mail messages to one or more SMTP servers.
• Once the transmission channel is established and initial handshaking completed, the SMTP client normally initiates a mail transaction. Such a transaction consists of a series of commands to specify the originator and destination of the mail and transmission of the message content (including any headers or other structure) itself.
• The server responds to each command with a reply; replies may indicate that the command was accepted, that additional commands are expected, or that a temporary or permanent error condition exists.
• Once a given mail message has been transmitted, the client may either request that the connection be shut down or may initiate other mail transactions.

Disadvantage/Problems

• SMTP does not require authentication. This allows anyone on internet to send email to anyone else or even large number of people. Because of this junk mails or spam mails are possible.
• If the client and server have different timeout then one of them may give up while other is still busy, unexpectedly terminate the connection.
• Older implementation cannot handle messages exceeding 64KB.