TCP IP Illustrated

Having a standard way of encoding all these values is

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Unformatted text preview: the client.) The verifier is used with secure RPC to identify the server. The accept status is 0 on success. A nonzero value can indicate an invalid version number or an invalid procedure number, for example. As with the RPC call message, if TCP is used instead of UDP, a 4-byte length field is sent between the TCP header and the XID. file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/nfs_netw.htm (4 of 23) [12/09/2001 14.47.56] Chapter 29. NFS: Network File System 29.3 XDR: External Data Representation XDR, External Data Representation, is the standard used to encode the values in the RPC call and reply messages-the RPC header fields (XID, program number, accept status, etc.), the procedure parameters, and the procedure results. Having a standard way of encoding all these values is what lets a client on one system call a procedure on a system with a different architecture. XDR is defined in RFC 1014 [Sun Microsystems 1987]. XDR defines numerous data types and exactly how they are transmitted in an RPC message (bit order, byte order, etc.). The sender must build an RPC message in XDR format, then the receiver converts the XDR format into its native representation. We see, for example, in Figures 29.1 and 29.2, that all the integer values we show (XID, call, program number, etc.) are 4-byte integers. Indeed, all integers occupy 4 bytes in XDR. Other data types supported by XDR include unsigned integers, booleans, floating point numbers, fixed-length arrays, variable-length arrays, and structures. 29.4 Port Mapper The RPC server programs containing the remote procedures use ephemeral ports, not wellknown ports. This requires a "registrar" of some form that keeps track of which RPC programs are using which ephemeral ports. In Sun RPC this registrar is called the port mapper. The term "port" in this name originates from the TCP and UDP port numbers, features of the Internet protocol suite. Since TI-RPC works over any transport layer, and not just TCP an...
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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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