RFC 2054 (rfc2054) - Page 2 of 16


WebNFS Client Specification



Alternative Format: Original Text Document



RFC 2054              WebNFS Client Specification           October 1996


   13.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . 16
   14.   Author's Address . . . . . . . . . . . . . . . . . . . . . 16

1. Introduction

   The NFS protocol provides access to shared filesystems across
   networks.  It is designed to be machine, operating system, network
   architecture, and transport protocol independent.  The protocol
   currently exists in two versions: version 2 [RFC 1094] and version 3
   [RFC 1813], both built on Sun RPC [RFC 1831] at its associated eXternal
   Data Representation (XDR) [RFC 1832] and Binding Protocol [RFC 1833].

   WebNFS provides additional semantics that can be applied to NFS
   version 2 and 3 to eliminate the overhead of PORTMAP and MOUNT
   protocols, make the protocol easier to use where firewall transit is
   required, and reduce the number of LOOKUP requests required to
   identify a particular file on the server. WebNFS server requirements
   are described in RFC 2055.

2. TCP vs UDP

   The NFS protocol is most well known for its use of UDP which performs
   acceptably on local area networks.  However, on wide area networks
   with error prone, high-latency connections and bandwidth contention,
   TCP is well respected for its congestion control and superior error
   handling.  A growing number of NFS implementations now support the
   NFS protocol over TCP connections.

   Use of NFS version 3 is particularly well matched to the use of TCP
   as a transport protocol.  Version 3 removes the arbitrary 8k transfer
   size limit of version 2, allowing the READ or WRITE of very large
   streams of data over a TCP connection.  Note that NFS version 2 is
   also supported on TCP connections, though the benefits of TCP data
   streaming will not be as great.

   A WebNFS client must first attempt to connect to its server with a
   TCP connection.  If the server refuses the connection, the client
   should attempt to use UDP.

3. Well-known Port

   While Internet protocols are generally identified by registered port
   number assignments, RPC based protocols register a 32 bit program
   number and a dynamically assigned port with the portmap service which
   is registered on the well-known port 111.  Since the NFS protocol is
   RPC-based, NFS servers register their port assignment with the
   portmap service.




Callaghan                    Informational