he UDP header on the front of your data, just as it would put a TCP header on the front of your data. Then UDP sends the data to IP, which adds the IP header, putting UDP's protocol number in the protocol field instead of TCP's protocol number. However UDP doesn't do as much as TCP does. It doesn't split data into multiple datagrams. It doesn't keep track of what it has sent so it can resend if necessary. About all that UDP provides is port numbers, so that several programs can use UDP at once. UDP port numbers are used just like TCP port numbers. There are well-known port numbers for servers that use UDP. Note that the UDP header is shorter than a TCP header. It still has source and destination port numbers, and a checksum, but that's about it. No sequence number, since it is not needed. UDP is used by the protocols that handle name lookups (see IEN 116, RFC 882, and RFC 883), and a number of similar protocols.B)Application layerApplication layer protocols include FTP Telnet RIP NFS HTTP SMTP and many others. These protocols are used to provide application level services. For example FTP defines a number of services for transferring files.*The following chapter will discuss the application protocols in more detail.SECTION 44.1 HARDWARE ADDRESSESA) Hardware addressesNetwork hardware use their own addressing schemes. For example every ethernet card has built into it a 48 bit address (called an Ethernet address or a Media Access Control, MAC, address). The high 24 bits of the address are used to assign a unique number to manufacturers of ethernet addresses and the low 24 bits are assigned to individual ethernet cards made by the manufacturer.Some example ethernet addresses are listed below ;00:00:0C:03:79:2F00:40:F6:60:4D:A400:20:AF:A4:55:8700:20:AF:A4:55:7B*Notice that the last two ethernet cards were made by the same manufacturer (with the manufacturers number of ).Every packet of information sent on ethernet contains a source and desti...
