TCP/IP Tutorial and Technical Overview - IBM Redbooks

several directories away. WebNFS can handle retrieving the entire path name
and evaluate it.
NFS URL
This scheme enables the NFS clients to go over the Internet, as do other Internet
applications. The URL scheme is based on the common Internet scheme syntax,
and is described in RFC 2224. The general form of the NFS URL scheme is:
nfs://:
The port is optional. If it is not specified, the default value is 2049. The WebNFS
server evaluates the path using a multicomponent lookup relative to the public
file handle.
14.5 The Andrew File System (AFS)
The Andrew File System (AFS) is a distributed file system used in
non-Distributed Computing Environments (DCEs). The DCE Distributed File
System (DFS) was based on AFS, and the two file systems are similar in
architecture. AFS offers high availability by storing information about more than
one server. It is also designed to work over WANs or the Internet, unlike NFS
version 3.
The latest version (AFS 3) has the following attributes:
► Single logical shared namespace
Every AFS user shares the same uniform name space. File names are
independent of both the user's and the file's physical locations. Groups of
client and server machines are known as cells.
► Client caching
Data is cached on client machines to reduce subsequent data requests
directed at file servers, which reduces network and server loads. Servers
keep track of client caches through callbacks, guaranteeing cache
consistency without constant queries to the server to see if the file has
changed.
► RPCs
AFS uses its Remote Procedure Call (RPC) reads and writes for efficient data
transfer across the network.
► Security
Kerberos-based authentication requires that users prove their identities
before accessing network services. When authenticated, AFS access control
lists (ACLs) give individual users or groups of users varying levels of authority
to perform operations on the files in a directory.
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