Transcript Manager

TCP/IP
Application Layer
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Comparison between OSI and TCP/IP
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Client-Server Model
(many-to-one)
Local machine
Remote machine
Client requests a service from a server
Client program runs when it is needed
Server program runs infinitely
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Bootstrap Protocol (BOOTP)
Dynamic Host Configuration Protocol (DHCP
• BOOTP – client-server protocol designed to
provide 4 pieces of information for a diskless
computer or a computer that is booted for the
first time.
A computer attached to TCP/IP must know the ff.
info:
– Its IP address
– Its subnet mask
– IP address of the router
– IP address of the server
• DHCP – extension of BOOTP
– Provides dynamic configuration
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DNS in the Internet
DNS –Domain Name System
Domain name –
name used instead
of address
3 sections of domain name space (tree)
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Generic Domains
Define registered
hosts
according to their
generic behavior
1st level label (3
character)
Organization types
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Country Domains
De Anza College in
Cupertino in California
in the United States
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Inverse Domain
Map an address to a name
Server list an IP address of
authorized clients.
Client sends a query to DNS
Server
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TERminal Network
(TELNET)
• Popular client-server application
program
– Enables the establishment of a connection
to remote system in such a way that the
local terminal appears to be a terminal at
the remote system.
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Local Login
Keystrokes are
accepted by the
terminal driver
Pass the
characters to
OS
OS interprets
the combination
of characters
and invokes the
application
program
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Remote Login
Transform the
characters to a
universal
character set
Network
virtual
terminal
characters
(NVT)
OS does not interpret the characters
Arrives at the TCP/IP
stack
Delivered to OS thru
pseudoterminal driver
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Concept of NVT
Network Virtual Terminal (NVT)
- universal interface
UNIX
Ctrl+z – suspend
Ctrl+c – abort
Ctrl+d – end-of-file
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DOS
Ctrl+z – end-of-file
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• Client TELNET translates characters to
NVT form
• Server TELNET translates NVT form
into characters acceptable by the
remote computer.
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FTP
- the standard mechanism provided by
TCP/IP for copying a file from one host
to another.
3 components of Client
Control connection – remains connected
Data connection – open and then closed for
each file transferred
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Trivial File Transfer Protocol
(TFTP)
-less funtionalities than FTP
ex. Diskless workstation or a router is
booted, we need to download the
bootstrap and configuration file
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SMTP Concept
Simple Mail Transfer Protocol
-supports e-mail
-Sending single message to 1 or more recipients
-Sending messages that include text, voice, video, graphics
-Sending messages to users on networks outside the internet
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UAs and MTs
User Agent & Mail Transfer Agent
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Relay MTAs
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Mail Gateways
Does not use
TCP/IP
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E-mail Address
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MIME
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POP3 and SMTP
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SNMP Concept
Simple Network Management Protocol
- for monitoring and maintaining an internet
Manager – management stations
- runs the SNMP client program
Agent – managed station
- routers/hosts that runs the
SNMP
server program
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• The agent keeps performance
information in a database.
– Ex. # of packets received and forwarded
• The manager can also make the router
perform certain actions
– Ex. Reboot the agent remotely at any time.
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• Management with SNMP is based on 3
basic ideas:
– A manager checks an agent by requesting
information that reflects the behavior of the
agent.
– A manager forces an agent to perform a
task by resetting values in the agent
database.
– An agent contributes to the management
process by warning the manager of the
unusual situation.
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Internet Management Components
Structure of Management Information (SMI)
Its functions are to name objects;
to define the type of data that can be stored in an object;
to show how to encode data for transmission over the network
Management Information Base (MIB)
A collection of all the objects that the manager can manage.
Each agent has its own MIB.
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Objects in MIB
System, interface, address, translation
Each group has defined variables and/or tables
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SNMP Messages
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SNMP Messages
• GetRequest – sent from the manager (client) to the agent
(server) to retrieve the value of a variable.
• GetResponse - sent from the agent to the manager in
response to GetRequest and GetNextRequest.
– It contains the value of the variable(s) requested by the
manager.
• SetRequest - sent from the manager to the agent to set (store)
a value in a variable.
• Trap – agent to manager – to report an event
– Ex. Agent is rebooted; reports the time of rebooting.
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