BOOTP computer science for multiproc.ppt

bootp

1. Bootp
AdeebaKH. Aboo
PhD.student
Seminar about bootp
supervised by:
prof.D.Manar
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2. 2
introduction
The information that is held in each computer attached
to a TCP/IP internet:
Its IP address
Its subnet mask
The IP address of a router
The IP address of a name server
Theaboveinformationisusuallystoredina
configurationfileandaccessedbythecomputerduringthe
bootstrapprocess
Inthecaseofadisklesscomputer,theoperatingsystem
andnetworkingcanbestoredinROM.Buttheabove
informationcannotbestoredinROM.

3. BOOTP
BOOTP(BootstrapProtocol)isclient/serverprotocol
designedtoprovidetheinformationforadisklesscomputer
oracomputerthatisbootedforthefirsttime
RARPprovidesonlytheIPaddressandnottheother
information
IfweuseBOOTP,wedonotneedRARP.
BOOTPisstatic.Whenaclientworkstationasksforthe
aboveinfo,itisretrievedfromafixedtable.Everytimethe
clientasksfortheinfo,itgetsthesameresults.
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4. BOOTP
UDP Ports
BOOTP is the client’s use of the well-known port 68
if two hosts with same well-known port 68 use BOOTP at the same
time in case of broadcasting the reply, both hosts receive the
message. In this case, transaction ID is used
Using TFTP
If a client needs more information for booting, the client can use the
pathname of a file sent by server which the client can find complete
booting information.
The client can then use a TFTP message to get the rest of the
needed information.
TCP/IP Protocol Suite 4

5. 5
Figure 1Client and server on the same network
BOOTP places its packet inside a UDP packet (note that BOOTP
is an application layer program).

6. Operation
Steps involved in use of
the BOOTP protocol
1) BOOTP server uses UDP port 67
and waiting for a client
2)The client sends a BOOTP request
message to the server. The client uses
(0s )as the source address and all( 1s)
as the destination address.
3)The server replies to the client with
Either a broadcast or a unicast message
using UDP destination port 68.
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7. 7
Figure 2Client and server on two different networks
When client and server are on different networks, we need a
relay agent, because client does not know IP address of
server,. Relay agent knows the IP addr of the server.

8. Bootp Format
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9. Bootp Format
•Operation code : request(1) or reply (0)
•Transaction ID : set by the client and used to match a reply
with the request
•Number of seconds : indicating the number of seconds
elapsed since the time the client started to boot
•Your IP address : client address filled by server (in the
client message)
•Server IP address : in a reply message
•Gateway IP address : IP address of a router in a reply
message.
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10. Bootp Format
•Server name : the domain name of the server in a reply
packet
•Boot filename : the full pathname of the boot in a reply
packet (128-byte)
•Options : used in a reply message (64-byte)
carrying either additional information (such as the
network mask or default router address) or some
specific information
in case of magic cookie, options have following options.
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11. Option format
TCP/IP Protocol Suite 11

12. Thank you
TCP/IP Protocol Suite 12