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Application Layer
Computer Networks
Tutun JuhanaTelecommunication EngineeringSchool of Electrical Engineering & InformaticsInstitut Teknologi Bandung
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HOST CONFIGURATION: DHCP
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Before DHCP
• RARP• BOOTP
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DHCP Operation
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DOMAIN NAME SYSTEM (DNS)
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Name Space• Flat Name Space
– In a flat name space, a name is assigned to an address
– A name in this space is a sequence of characters without structure.
– The main disadvantage : it cannot be used in a large system because it must be centrally controlled to avoid ambiguity and duplication
• Hierarchical Name Space– Each name is made of several parts– A central authority can assign the part of the name
that defines the nature of the organization and the name of the organization
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Domain Name Space
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Domain
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Distribution of Name Space
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DNS in the Internet
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Resolution
• Mapping a name to an address or an address to a name is called name-address resolution.
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Resolver
• DNS is designed as a client-server application• A host that needs to map an address to a name or a
name to an address calls a DNS client called a resolver• The resolver accesses the closest DNS server with a
mapping request• If the server has the information, it satisfies the resolver;
otherwise, it either refers the resolver to other servers or asks other servers to provide the information
• After the resolver receives the mapping, it interprets the response to see if it is a real resolution or an error, and finally delivers the result to the process that requested it
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Caching
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Types of Records
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TELNET AND SSH
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Telnet
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SSH
• Secure Shell
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Port Forwarding
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FTP
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WWW AND HTTP
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Web Client (Browser)
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Web Server
• Uniform Resource Locator (URL)
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Web Document
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HTTP
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Cookies
• The World Wide Web was originally designed as a stateless entity
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ELECTRONIC MAIL:SMTP, POP, IMAP, AND MIME
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Architecture
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User Agent (UA)
• It provides service to the user to make the process of sending and receiving a message easier.
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Message Transfer Agent: SMTP
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Mail Transfer Phases
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Message Access Agent: POP AND IMAP
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POP3Post Office Protocol, version 3
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IMAP4Internet Mail Access Protocol, version 4
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MIME
• Multipurpose Internet Mail Extensions (MIME) is a supplementary protocol that allows non-ASCII data to be sent through e-mail
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Web-based mail
