Overview of the TFTP protocol.
TFTP (Trivial File Transfer Protocol) is, as its name implies, a very simple mechanism for transferring files between 2 hosts.
TFTP is typically used for downloading software and configuration files to Internet and LAN appliances like routers, switches and gateways.
Due to its simplicity, TFTP is often contained in bootloader programs that need to have a very small memory footprint in order to fit into EEPROM style chips.
TFTP is not a reduced version or predecessor of FTP. TFTP and FTP do not have anything in common and serve different purposes. While FTP comes with some minimal access and session control and other features, TFTP is barely a file transport mechanism.
Overview of the TFTP protocol.
TFTP (Trivial File Transfer Protocol) is, as its name implies, a very simple mechanism for transferring files between 2 hosts.
TFTP is typically used for downloading software and configuration files to Internet and LAN appliances like routers, switches and gateways.
Due to its simplicity, TFTP is often contained in bootloader programs that need to have a very small memory footprint in order to fit into EEPROM style chips.
TFTP is not a reduced version or predecessor of FTP. TFTP and FTP do not have anything in common and serve different purposes. While FTP comes with some minimal access and session control and other features, TFTP is barely a file transport mechanism.
Lecture 6 The Communication System Finalterm Slides
Chap 18 telnet
1. CChhaapptteerr 1188
RReemmoottee LLooggiinn::
TTeellnneett
Objectives
Upon completion you will be able to:
• Understand how TELNET works
• Understand the role of NVT in a TELNET communication
• Understand TELNET option and suboption negotiation
• Know how control characters are used
• Know the TELNET modes of operation
TCP/IP Protocol Suite 1
2. NNoottee::
TELNET is a general-purpose
client-server application program.
TCP/IP Protocol Suite 2
3. 18.1 CONCEPT
TELNET enables the establishment of a connection ttoo aa rreemmoottee ssyysstteemm
iinn ssuucchh aa wwaayy tthhaatt tthhee llooccaall tteerrmmiinnaall aappppeeaarrss ttoo bbee aa tteerrmmiinnaall aatt tthhee
rreemmoottee ssyysstteemm..
TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee::
TTiimmee--SShhaarriinngg EEnnvviirroonnmmeenntt
LLooggiinn
TCP/IP Protocol Suite 3
8. 18.3 NVT CHARACTER SET
NVT uses two sets of characters, one for data and oonnee ffoorr ccoonnttrrooll.. BBootthh
aarree 88--bbiitt bbyytteess..
TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee::
DDaattaa CChhaarraacctteerrss
CCoonnttrrooll CChhaarraacctteerrss
TCP/IP Protocol Suite 8
12. 18.4 EMBEDDING
The same connection is used by TELNET for sending bbootthh ddaattaa aanndd
ccoonnttrrooll cchhaarraacctteerrss.. TTEELLNNEETT aaccccoommpplliisshheess tthhiiss bbyy eemmbbeeddddiinngg tthhee ccoonnttrrooll
cchhaarraacctteerrss iinn tthhee ddaattaa ssttrreeaamm..
TCP/IP Protocol Suite 12
13. Figure 18.6 An example of embedding
TCP/IP Protocol Suite 13
14. 18.5 OPTIONS
TELNET lets the client and server negotiate options bbeeffoorree oorr dduurriinngg tthhee
uussee ooff tthhee sseerrvviiccee.. OOppttiioonnss aarree eexxttrraa ffeeaattuurreess aavvaaiillaabbllee ttoo aa uusseerr wwiitthh aa
mmoorree ssoopphhiissttiiccaatteedd tteerrmmiinnaall..
TCP/IP Protocol Suite 14
22. ExamplE 1
Figure 18.11 shows an example of option negotiation. In this
example, the client wants the server to echo each character
sent to the server. In other words, when a character is typed at
the user keyboard terminal, it goes to the server and is sent
back to the screen of the user before being processed. The echo
option is enabled by the server because it is the server that
sends the characters back to the user terminal. Therefore, the
client should request from the server the enabling of the option
using DO. The request consists of three characters: IAC, DO,
and ECHO. The server accepts the request and enables the
option. It informs the client by sending the three character
approval: IAC, WILL, and ECHO.
See Next Slide
TCP/IP Protocol Suite 22
32. 18.10 ESCAPE CHARACTER
When a user wants characters interpreted by the client iinnsstteeaadd ooff tthhee
sseerrvveerr,, hhee ccaann uussee aann eessccaappee cchhaarraacctteerr,, nnoorrmmaallllyy CCttrrll++]] ((sshhoowwnn aass ^^]]))..
TCP/IP Protocol Suite 32
33. Figure 18.15 Two different interruptions
TCP/IP Protocol Suite 33
34. 18.11 MODE OF OPERATION
Most TELNET implementations operate in one ooff tthhrreeee mmooddeess:: ddeeffaauulltt
mmooddee,, cchhaarraacctteerr mmooddee,, oorr lliinnee mmooddee..
TThhee ttooppiiccss ddiissccuusssseedd iinn tthhiiss sseeccttiioonn iinncclluuddee::
DDeeffaauulltt MMooddee
CChhaarraacctteerr MMooddee
LLiinnee MMooddee
TCP/IP Protocol Suite 34
35. ExamplE 2
In this example, we use the default mode to show the concept
and its deficiencies even though it is almost obsolete today. The
client and the server negotiate the terminal type and terminal
speed and then the server checks the login and password of the
user (see Figure 18.16).
See Next Slide
TCP/IP Protocol Suite 35
37. ExamplE 3
In this example, we show how the client switches to the
character mode. This requires that the client request the server
to enable the SUPPRESS GO AHEAD and ECHO options (see
Figure 18.17).
See Next Slide
TCP/IP Protocol Suite 37