TCP IP Illustrated

0 then broadcasts from this misconfigured host appear

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Unformatted text preview: t its subnet mask sends all its "local" broadcasts to all subnets. For example, if the host with IP address 128.1.2.3 doesn't set a subnet mask, then its broadcast address normally defaults to 128.1.255.255. But if the subnet mask should have been set to 255.255.255.0, then broadcasts from this misconfigured host appear directed to all subnets. The first widespread implementation of TCP/IP, the 4.2BSD system in 1983, used a host ID of all zero bits for the broadcast address. One of the earliest references to the broadcast IP address is IEN 212 [Gurwitz and Hinden 1982], and it proposed to define the IP broadcast address as a host ID of one bits. (lENs are the Internet Experiment Notes, basically predecessors to the RFCs.) RFC 894 [Hornig 1984] commented that 4.2BSD used a nonstandard broadcast address, but RFC 906 [Finlayson 1984] noted that there was no Internet standard for the broadcast address. The RFC editor added a footnote to RFC 906 acknowledging the lack of a standard broadcast address, but strongly recommended that a host ID of all file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/broadcas.htm (4 of 12) [12/09/2001 14.47.00] Chapter 12. Broadcasting and Multicasting one bits be used as the broadcast address. Although Berkeley adopted the use of all one bits for the broadcast address with 4.3BSD in 1986, some operating systems (notably SunOS 4.x) continued to use the nonstandard broadcast address through the early 1990s. 12.3 Broadcasting Examples How are broadcasts sent and what do routers and hosts do with broadcasts? Unfortunately this is a hard question to answer because it depends on the type of broadcast address, the application, the TCP/IP implementation, and possible configuration switches. First, the application must support broadcasting. If we execute sun % ping 255.255.255.255 /usr/etc/ping: unknown host 255.255.255.255 intending to send a broadcast on the local cable, it doesn't work. But the problem here is a programming problem in th...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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