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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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public file h<strong>and</strong>les <strong>and</strong> the LOOKUP, allowing the NFSv4 protocol to mount file<br />

systems without invoking additional protocols. Additionally, NFSv4 integrates<br />

locking schemes into the base NFS protocol, <strong>and</strong> therefore no longer relies upon<br />

the Lock Manager protocol. These integrations are transparent to users.<br />

Introduction of stateful operations<br />

Previous versions of NFS were considered stateless. However, with NFSv4,<br />

OPEN <strong>and</strong> CLOSE operations were added, creating a concept of statefulness on<br />

the NFS server. This addition provides numerous advantages over the stateless<br />

model, including:<br />

► The ability to integrate enhanced locking functionality<br />

► The ability for a server to delegate authority to a client<br />

► Allowing aggressive caching of file data<br />

The total number of operations in NFSv4 has exp<strong>and</strong>ed to 38. Many of these<br />

perform functions similar to those provided in previous releases of NFS, but new<br />

operations have been added to integrating locking, security, <strong>and</strong> client access.<br />

Examples of some these include:<br />

lock Creates a lock on a file.<br />

lockt Tests for the existence of a lock on a file.<br />

lucku Unlocks a file.<br />

secinfo Retrieves NFS security information.<br />

Security enhancements<br />

In version 4, NFS now takes advantage of available security methods, including:<br />

► Support for RPCSEC_GSS, described in RFC 2203<br />

► Support for Kerberos 5, described in RFC 4120<br />

► Support for the Low Infrastructure Public Key Mechanism (L<strong>IP</strong>KEY), defined<br />

in RFC 2847<br />

► Support for the Simple Public-Key GSS-API Mechanism (SPKM-3), defined in<br />

RFC 2025<br />

Additional changes<br />

The following additional changes, which do not fit into the previous discussions of<br />

NFSv4, are worth noting:<br />

► New volatile style file h<strong>and</strong>les, which help server implementations cope with<br />

file system reorganizations<br />

544 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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