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CS4550 Computer Networks II

Topics In Applications

Ref: Feit Chap 13-20Tanenbaum Chap 7

Clients, requestor programs Servers, demon, reply peerT

elne

t

FT

P

SN

MP

E-m

ail

WW

W

Tel

net

FT

P

SN

MP

E-m

ail

WW

W

TCP UDP

IP

DL and physical

TCP UDP

IP

DL and physical

From Port 23

From Protocol 6

To port 23

To protocol 6

General Architecture

Common Tools

Ping Echo 7/udp

netstat time 13/udp

traceroute tracert quote 17/udp

TELNET

First Application

Connect as a terminal to a networked host

Terminal emulation

Telnet to selected port

Commands

Connect as a terminal to a networked host

NVT - Network Virtual Terminal Solves Multi vendor problem

NVT code - 7 bit USASCII 128 characters

Line Format- half duplex, stop and wait, <CR><LF>

Command Format - Interpret As Command (IAC)

Escape character IAC = 255 note 8’th bit set

IAC Command option

255 251 24

will terminal type

Terminal emulation

Telnet cs.nps.navy.mil 7 echo service

telnet cs.nps.navy.mil 13 time of day service

telnet cs.nps.navy.mil 80 www service

telnet cs.nps.navy.mil 25 mail service

type help

Connect to a selected port

Telnet Commandsget a list of commands

Wolf> telnet

telnet > ?