Transcript IST 201 - John Rouda

IST 201
Chapter 11
Lecture 2
Ports
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Used by TCP & UDP
Keep track of different types of transmissions
crossing the network simultaneously.
Combination of IP address & port number is
referred to as a socket.
Pass info to upper layer protocols
Transmissions that originate w/o a known
appl. port # get a dynamically assigned port
number greater than 1023.
TCP – Transmission Control Protocol
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Operates @ transport layer
Part of the TCP/IP protocol suite
Connection – oriented
Breaks messages (data) into segments
Passes to next layer
Reassembles segments into messages
TCP Protocols
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FTP
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Port #53
Domain Name Service, System, Server
Telnet
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Port #25
Simple Mail Transfer Protocol
DNS
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Port #80
Hypertext Transfer Protocol
SMTP
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File Transport Protocol
HTTP
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Port #21, #20
Port #23
Terminal network
TCP Segment Format
Bit 15 Bit 16
Bit 0
Source Port (16)
Bit 31
Destination Port (16)
Sequence Number (32)
Acknowledgment Number (32)
Header
Reserved Code
Window (16)
Length (4)
(6)
Bits (6)
Checksum (16)
Urgent (16)
Options (0 or 32 if Any)
Data (Varies)
20
Bytes
UDP – User Datagram Protocol
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Operates @ transport layer
Part of the TCP/IP protocol suite
Connectionless
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No acknowledgements; no receipts
Error handling & retransmission must
be handled by upper layer protocols.
UDP Segment Format
Bit 15 Bit 16
Bit 0
Source Port (16)
Bit 31
Designated Router (16)
Length (16)
Checksum (16)
Data (If Any)
No Sequence or Acknowledgement Fields
8
Bytes
UDP Protocols
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TFTP – Port 69
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SNMP – Port 161
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Simple Network Management Protocol
DHCP – Port 67, Port 68
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Trivial File Transport Protocol
Dynamic Host Configuration Protocol
DNS – Port 53
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Domain Name Server, System, Service
Application Layer
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Closest layer to end user
Intermediary between user’s software
applications
Provides services to application software
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Spreadsheets
Word processing
Banking
Direct interface to web browsers, e-mail
Application Layer
Responsibilities
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Identify and establish availability of
intended communication partners
Synchronize co-operating applications
Establish agreement on procedures for
error recovery
Control data integrity
Direct Network Applications
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Server
Application that
operate on
client/server
network
Examples
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FTP
Web browsers
E-mail
Client
Server
Indirect Network
Using a host application – word
processing, spreadsheet, etc. and
opening, printing or saving to a
network server.
Client
Make/Break a Connection
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Alternative to connection-oriented and
connectionless
Examples
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Accessing a web page
Printing to a network server
DNS – Domain Name Service
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System used on the Internet to
translate domain names to IP addresses
Each LAN usually has a least one DNS
server
.us
.mil
.edu
.org
.com
.net
.gov
FTP
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Download/upload files
Client/server application
Server must have the FTP software running
for clients to be able to access it.
Requires authentication
Establishes a connection – uses TCP
Commands are sent and executed on the
server
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Create folders, copy, move, erase, rename files
TFTP
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Connectionless – uses UDP
Small, easy to implement
File downloads/uploads
Read/write files only
Fast
HTTP
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Works with the WWW
Browser is client/server application
Make/break a connection
SMTP
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E-mail servers communicate with one another
to send/receive mail
Supplies little security
No authentication required
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POP3 (Port 110) or IMAP4
Clients use to download mail
Both use TCP
Clients use SMTP to send mail
Clients use POP3 or IMAP4 to receive
SNMP
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Allows the exchange of management
information between network devices
Manage network performance
Find/resolve network problems
Plan for growth
SNMP Components
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Managed device
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Network node w/SNMP agent installed to collect
and store local information
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Agent
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Routers, servers, switches, hubs, hosts, printers
Software module that reside on a managed device
Network Management System
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Executes applications that monitor and control
devices
Usually resides on a server; processing and
memory resources there primarily used
Telnet
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Terminal emulation software that allows
the capability to remotely access
another device
Commonly used to manage network
devices
Client – local host
Server – remote host
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Special software called a daemon