Chapter 9. Applications and Network Management

Having presented basic concepts and definitions in networking to the point that an end-to-end connection can be established, we now look at the last layer of the protocol stackthe application layer and certain network-management issues. This chapter examines Internet applications and their supporting protocols and services. These services demonstrate how users perceive a computer network and express the power of Internet technology. This chapter focuses on the following topics:

• Application-layer overview

• Domain Name System (DNS)

• Remote login protocols

• Electronic mail (e-mail)

• File transfer and FTP

• World Wide Web (WWW) and HTTP

• Network management

Layer 5, the application layer , determines how a specific user application should use a network. The Domain Name System (DNS) server is an essential entity for translating machine or domain names into numerical IP addresses. Remote login protocols allow applications to run at a remote site, with results transferred back to their local sites. Two remote login protocols are TELNET and SSH.

The most-applied Internet tool is e-mail . The Simple Mail Transfer Protocol (SMTP) is one of the protocols for sending electronic mail (e-mail) from the mail server of a source to the mail servers of destinations. The World Wide Web (WWW), or simply Web , is a global network of servers linked together by protocols allowing access to all connected hypertext resources.

Finally, this chapter discusses network management. ASN.1 is a formal language for each managed device to be defined in a network under management. MIB is another management tool for accommodating a database of information and characteristics for devices. The Simple Network Management Protocol (SNMP) enables a network manager to find the location of a fault. SNMP runs on top of UDP and uses client/server configurations. SNMP commands define how to query information from a server and forward information to a server or a client.