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Unformatted text preview: tions. A new protocol named DHCP (Dynamic Host Configuration Protocol) is built
on, but replaces, BOOTP. DHCP extends this area to 312 bytes and is defined in RFC 1541
[Droms 1993]. 16.7 Summary
BOOTP uses UDP and is intended as an alternative to RARP for bootstrapping a diskless
system to find its IP address. BOOTP can also return additional information, such as the IP
address of a router, the client's subnet mask, and the IP address of a name server.
Since BOOTP is used in the bootstrap process, a diskless system needs the following protocols
implemented in read-only memory: BOOTP, TFTP, UDP, IP, and a device driver for the local
The implementation of a BOOTP server is easier than an RARP server, since BOOTP requests
and replies are in UDP datagrams, not special link-layer frames. A router can also serve as a
proxy agent for a real BOOTP server, forwarding client requests to the real server on a
16.1 We've said that one advantage of BOOTP over RARP is that BOOTP can work through
routers, whereas RARP, which is a link-layer broadcast, cannot. Yet in Section 16.5 we had to
define special ways for BOOTP to work through a router. What would happen if a capability
were added to routers allowing them to forward RARP requests?
16.2 We said that a BOOTP client must use the transaction ID to match responses with
requests, in case there are multiple clients bootstrapping at the same time from a server that
broadcasts replies. But in Figure 16.3 the transaction ID is 0, implying that this client ignores
the transaction ID. How do you think this client matches the responses with its requests? file:///D|/Documents%20and%20Settings/bigini/Documenti/homenet2run/tcpip/tcp-ip-illustrated/bootp.htm (9 of 9) [12/09/2001 14.47.08] Chapter 17. TCP: Transmission Control Protocol TCP: Transmission Control Protocol
In this chapter we provide a description of the services provided by TCP for the application
layer. We also look at the fields in the TCP header. In the chapters that follow we examine
all of these header fields in more...
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- Spring '12