TCP IP Illustrated

Htm 4 of 4 12092001 144707 chapter 16 bootp bootstrap

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: t this? 15.3 We said that the TFTP sender performs the timeout and retransmission to handle lost packets. How does this affect the use of TFTP when it's being used as part of the bootstrap process? 15.4 What is the limiting factor in the time required to transfer a file using TFTP? file:///D|/Documents%20and%20Settings/bigini/Documenti/homenet2run/tcpip/tcp-ip-illustrated/tftp_tri.htm (4 of 4) [12/09/2001 14.47.07] Chapter 16. BOOTP: Bootstrap Protocol BOOTP: Bootstrap Protocol 16.1 Introduction In Chapter 5 we described how a diskless system, with no knowledge of its IP address, can determine its IP address using RARP when it is bootstrapped. There are two problems with RARP: (1) the only thing returned is the IP address, and (2) since RARP uses a link-layer broadcast, RARP requests are not forwarded by routers (necessitating an RARP server on every physical network). This chapter describes an alternative method for a diskless system to bootstrap itself, called the Bootstrap Protocol, or BOOTP. BOOTP uses UDP and normally works in conjunction with TFTP (Chapter 15). RFC 951 [Croft and Gilmore 1985] is the official specification for BOOTP with clarifications given in RFC 1542 [Wimer 1993]. 16.2 BOOTP Packet Format BOOTP requests and replies are encapsulated in UDP datagrams, as shown in Figure 16.1. Figure 16.1 Encapsulation of BOOTP requests and replies within a UDP datagram. Figure 16.2 shows the format of the 300-byte BOOTP request and reply. file:///D|/Documents%20and%20Settings/bigini/Documenti/homenet2run/tcpip/tcp-ip-illustrated/bootp.htm (1 of 9) [12/09/2001 14.47.08] Chapter 16. BOOTP: Bootstrap Protocol Figure 16.2 Format of BOOTP request and reply. Opcode is 1 for a request and 2 for a reply. The hardware type field is 1 for a 10 Mbits/sec Ethernet, the same value that is in the field of the same name in an ARP request or reply (Figure 4.3). Similarly, the hardware address length is 6 bytes for an Ethernet. The hop count is set to 0 by the client, but can be used...
View Full Document

Ask a homework question - tutors are online