Network Working Group B. Callaghan
INTERNET DRAFT
Category: Informational
Expire in six months Sun Microsystems, Inc.
October 1996
WebNFS Client Specification
<draft-callaghan-webnfs-client-00.txt>
Abstract
This document describes a lightweight binding mechanism that
allows NFS clients to obtain service from WebNFS-enabled
servers with a minimum of protocol overhead. In removing
this overhead, WebNFS clients see benefits in faster response
to requests, easy transit of packet filter firewalls and
TCP-based proxies, and better server scalability.
Status of this Memo
This memo provides information for the Internet community.
This memo does not specify an Internet standard of any kind.
Distribution of this memo is unlimited.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 2
2. TCP vs UDP . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Well-known Port . . . . . . . . . . . . . . . . . . . . . 2
4. NFS Version 3 . . . . . . . . . . . . . . . . . . . . . . 3
4.1 Transfer Size . . . . . . . . . . . . . . . . . . . . . 3
4.2 Fast Writes . . . . . . . . . . . . . . . . . . . . . . 4
4.3 READDIRPLUS . . . . . . . . . . . . . . . . . . . . . . 5
5. Public Filehandle . . . . . . . . . . . . . . . . . . . . 5
5.1 NFS Version 2 Public Filehandle . . . . . . . . . . . . 5
5.2 NFS Version 3 Public Filehandle . . . . . . . . . . . . 6
6. Multi-component Lookup . . . . . . . . . . . . . . . . . . 6
6.1 Canonical Path vs. Native Path . . . . . . . . . . . . . 7
6.2 Symbolic Links . . . . . . . . . . . . . . . . . . . . . 8
6.2.1 Absolute Link . . . . . . . . . . . . . . . . . . . . 8
6.2.2 Relative Link . . . . . . . . . . . . . . . . . . . . 8
6.3 Filesystem Spanning Pathnames . . . . . . . . . . . . . 9
7. Contacting the Server . . . . . . . . . . . . . . . . . . 10
8. Mount Protocol . . . . . . . . . . . . . . . . . . . . . . 11
9. Exploiting Concurrency . . . . . . . . . . . . . . . . . . 12
9.1 Read-ahead . . . . . . . . . . . . . . . . . . . . . . . 12
9.2 Concurrent File Download . . . . . . . . . . . . . . . . 13
10. Timeout and Retransmission . . . . . . . . . . . . . . . . 14
11. Bibliography . . . . . . . . . . . . . . . . . . . . . . . 15
12. Security Considerations . . . . . . . . . . . . . . . . . 16
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 17
14. Author's Address . . . . . . . . . . . . . . . . . . . . . 17
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 [RFC1094]
and version 3 [RFC1813], both built on Sun RPC [RFC1831] at its
associated eXternal Data Representation (XDR) [RFC1832] and
Binding Protocol [RFC1833].
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 mmmm.
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.
NFS servers are constrained by a requirement to re-register
at the same port after a server crash and recovery so that
clients can recover simply by retransmitting an RPC request
until a response is received. This is simpler than the
alternative of having the client repeatedly check with
the portmap service for a new port assignment. NFS servers
typically achieve this port invariance by registering a
constant port assignment, 2049, for both UDP and TCP.
To avoid the overhead of contacting the server's portmap
service, and to facilitate transit through packet filtering
firewalls, WebNFS clients optimistically assume that WebNFS
servers register on port 2049. Most NFS servers use this
port assignment already, so this client optimism is well
justified. Refer to section 8 for further details on port
binding.
4. NFS Version 3
NFS version 3 corrects deficiencies in version 2 of the protocol
as well as providing a number of features suitable to WebNFS
clients accessing servers over high-latency, low-bandwidth
connections.
4.1 Transfer Size
NFS version 2 limited the amount of data in a single request
or reply to 8 kilobytes. This limit was based on what was
then considered a reasonable upper bound on the amount of
data that could be transmitted in a UDP datagram across an
Ethernet. The 8k transfer size limitation affects READ, WRITE,
and READDIR requests. When using version 2, a WebNFS client
must not transmit any request that exceeds the 8k transfer
size. Additionally, the client must be able to adjust its
requests to suit servers that limit transfer sizes to values
smaller than 8k.
NFS version 3 removes the 8k limit, allowing the client and
server to negotiate whatever limit they choose. Larger
transfer sizes are preferred since they require fewer READ
or WRITE requests to transfer a given amount of data and
utilize a TCP stream more efficiently.
While the client can use the FSINFO procedure to request the
server's maximum and preferred transfer sizes, in the
interests of keeping the number of NFS requests to a
minimum, WebNFS clients should optimistically choose a
transfer size and make corrections if necessary based on the
server's response.
For instance, given that the file attributes returned with
the filehandle from a LOOKUP request indicate that the file
has a size of 50k, the client might transmit a READ request
for 50k. If the server returns only 32k, then the client
can assume that the server's maximum transfer size is 32k
and issue another read request for the remaining data.
The server will indicate positively when the end of file
is reached.
A similar strategy can be used when writing to a file on
the server, though the client should be more conservative
in choosing write request sizes so as to avoid transmitting
large amounts of data that the server cannot handle.
4.2 Fast Writes
NFS version 2 requires the server to write client data
to stable storage before responding to the client.
This avoids the possibility of the the server crashing
and losing the client's data after a positive response.
While this requirement protects the client from data
loss, it requires that the server direct client write
requests directly to the disk, or to buffer client data
in expensive non-volatile memory (NVRAM). Either way,
the effect is poor write performance, either through
inefficient synchronous writes to the disk or through the
limited buffering available in NVRAM.
NFS version 3 provides clients with the option of having the
server buffer a series of WRITE requests in unstable storage.
A subsequent COMMIT request from the client will have the
server flush the data to stable storage and have the client
verify that the server lost none of the data. Since fast
writes benefit both the client and the server, WebNFS clients
should use WRITE/COMMIT when writing to the server.
4.3 READDIRPLUS
The NFS version 2 READDIR procedure is also supported in
version 3. READDIR returns the names of the entries in
a directory along with their fileids. Browser programs that
display directory contents as a list will usually display
more than just the filename; a different icon may be displayed
if the entry is a directory or a file. Similarly, the browser
may display the file size, and date of last modification.
Since this additional information is not returned by READDIR,
version 2 clients must issue a series of LOOKUP requests, one
per directory member, to retrieve the attribute data. Clearly
this is an expensive operation where the directory is large
(perhaps several hundred entries) and the network latency is high.
The version 3 READDIRPLUS request allows the client to retrieve
not only the names of the directory entries, but also their
file attributes and filehandles in a single call. WebNFS clients
that require attribute information for directory entries should
use READDIRPLUS in preference to READDIR.
5. Public Filehandle
NFS filehandles are normally created by the server and used
to identify uniquely a particular file or directory on the server.
The client does not normally create filehandles or have any
knowledge of the contents of a filehandle.
The public filehandle is an an exception. It is an NFS filehandle
with a reserved value and special semantics that allow an initial
filehandle to be obtained. A WebNFS client can use the public
filehandle as an initial filehandle rather than using the MOUNT
protocol. Since NFS version 2 and version 3 have different
filehandle formats, the public filehandle is defined differently
for each.
The public filehandle is a zero filehandle. For NFS version 2
this is a filehandle with 32 zero octets. A version 3 public
filehandle has zero length.
5.1 NFS Version 2 Public Filehandle
A version 2 filehandle is defined in RFC 1094 as an opaque value
occupying 32 octets. A version 2 public filehandle has a zero
in each octet, i.e. all zeros.
1 32
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.2 NFS Version 3 Public Filehandle
A version 3 filehandle is defined in RFC 1813 as a variable length
opaque value occupying up to 64 octets. The length of the filehandle
is indicated by an integer value contained in a 4 octet value
which describes the number of valid octets that follow. A version
3 public filehandle has a length of zero.
+-+-+-+-+
| 0 |
+-+-+-+-+
6. Multi-component Lookup
Normally the NFS LOOKUP request (version 2 or 3) takes
a directory filehandle along with the name of a directory
member, and returns the filehandle of the directory member.
If a client needs to evaluate a pathname that contains
a sequence of components, then beginning with the directory
filehandle of the first component it must issue a series of LOOKUP
requests one component at a time. For instance, evaluation of
the Unix path "a/b/c" will generate separate LOOKUP requests for
each component of the pathname "a", "b", and "c".
A LOOKUP request that uses the public filehandle can provide
a pathname containing multiple components. The server is
expected to evaluate the entire pathname and return a filehandle
for the final component. Both canonical (slash-separated) and
server native pathnames are supported.
For example, rather than evaluate the path "a/b/c" as:
LOOKUP FH=0x0 "a" --->
<--- FH=0x1
LOOKUP FH=0x1 "b" --->
<--- FH=0x2
LOOKUP FH=0x2 "c" --->
<--- FH=0x3
Relative to the public filehandle these three LOOKUP
requests can be replaced by a single multi-component
lookup:
LOOKUP FH=0x0 "a/b/c" --->
<--- FH=0x3
Multi-component lookup is supported only for LOOKUP
requests relative to the public filehandle.
6.1 Canonical Path vs. Native Path
If the pathname in a multi-component LOOKUP request begins
with an ASCII character, then it must be a canonical path.
A canonical path is a hierarchically-related, slash-separated
sequence of components, <directory>/<directory>/.../<name>.
Occurrences of the "/" character within a component must be
escaped using the escape code %2f. Non-ascii characters within
components must also be escaped using the "%" character to
introduce a two digit hexadecimal code. Occurrences of the "%"
character that do not introduce an encoded character must themselves
be encoded with %25.
If the first character of the path is a slash, then the canonical
path will be evaluated relative to the server's root directory.
If the first character is not a slash, then the path will be
evaluated relative to the directory with which the public
filehandle is associated.
Not all WebNFS servers can support arbitrary use of absolute
paths. Clearly, the server cannot return a filehandle if
the path identifies a file or directory that is not exported
by the server. In addition, some servers will not return
a filehandle if the path names a file or directory in an
exported filesystem different from the one that is associated
with the public filehandle.
If the first character of the path is 0x80 (non-ascii) then
the following character is the first in a native path.
A native path conforms to the normal pathname syntax of the
server. For example:
Lookup for Canonical Path:
LOOKUP FH=0x0 "/a/b/c"
Lookup for Native Path:
LOOKUP FH=0x0 0x80 "a:b:c"
6.2 Symbolic Links
On Unix servers, components within a pathname may be symbolic
links. The server will evaluate these symbolic links as a part
of the normal pathname evaluation process. If the final
component is a symbolic link, the server will return its filehandle,
rather than evaluate it.
If the attributes returned with a filehandle indicate that
it refers to a symbolic link, then it is the client's
responsibility to deal with the link by fetching the contents
of the link using the READLINK procedure. What follows is
determined by the contents of the link.
Evaluation of symbolic links by the client is defined only
if the symbolic link is retrieved via the multi-component
lookup of a canonical path.
6.2.1 Absolute Link
If the first character of the link text is a slash "/", then
the following path can be assumed to be absolute. The entire path
must be evaluated by the server relative to the public filehandle:
LOOKUP FH=0x0 "a/b" --->
<--- FH=0x1 (symbolic link)
READLINK FH=0x1 --->
<--- "/x/y"
LOOKUP FH=0x0 "/x/y"
<--- FH=0x2
So in this case the client just passes the link text back
to the server for evaluation.
6.2.2 Relative Link
If the first character of the link text is not a slash, then
the following path can be assumed to be relative to the location
of the symbolic link. To evaluate this correctly, the client
must substitute the link text in place of the final pathname
component that named the link and issue a another LOOKUP relative
to the public filehandle.
LOOKUP FH=0x0 "a/b" --->
<--- FH=0x1 (symbolic link)
READLINK FH=0x1 --->
<--- "x/y"
LOOKUP FH=0x0 "a/x/y"
<--- FH=0x2
By substituting the link text in the link path and having
the server evaluate the new path, the server effectively
gets to evaluate the link relative to the link's location.
The client may also "clean up" the resulting pathname by
removing redundant components as described in Section 4. of
RFC 1808.
6.3 Filesystem Spanning Pathnames
NFS LOOKUP requests normally do not cross from one
filesystem to another on the server. For instance
if the server has the following export and mounts:
/export (exported)
/export/bigdata (mountpoint)
then an NFS LOOKUP for "bigdata" using the filehandle for
"/export" will return a "no file" error because the LOOKUP
request did not cross the mountpoint on the server. There
is a practical reason for this limitation: if the server
permitted the mountpoint crossing to occur, then a Unix client
might receive ambiguous fileid information inconsistent with
it's view of a single remote mount for "/export". It is
expected that the client resolve this by mirroring the additional
server mount, e.g.
Client Server
/mnt <--- mounted on --- /export
/mnt/bigdata <--- mounted on --- /export/bigdata
However, this semantic changes if the client issues
the filesystem spanning LOOKUP relative to the public
filehandle. If the following filesystems are exported:
/export (exported public)
/export/bigdata (exported mountpoint)
then an NFS LOOKUP for "bigdata" relative to the public
filehandle will cross the mountpoint - just as if the
client had issued a MOUNT request - but only if the
new filesystem is exported, and only if the server
supports Export Spanning Pathnames described in Section 6.3
of RFC [mmmm].
7. Contacting the Server
WebNFS clients should be optimistic in assuming that the server
supports WebNFS, but should be capable of fallback to
conventional methods for server access if the server does not
support WebNFS.
The client should start with the assumption that the
server supports:
- NFS version 3.
- NFS TCP connections.
- Public Filehandles.
If these assumptions are not met, the client should
fall back gracefully with a minimum number of
messages. The following steps are recommended:
1. Attempt to create a TCP connection to the server's
port 2049.
If the connection fails then assume that a request
sent over UDP will work. Use UDP port 2049.
Do not use the PORTMAP protocol to determine the
server's port unless the server does not respond to
port 2049 for both TCP and UDP.
2. Assume WebNFS and V3 are supported.
Send an NFS version 3 LOOKUP with the public filehandle
for the requested pathname.
If the server returns an RPC PROG_MISMATCH error then
assume that NFS version 3 is not supported. Retry
the LOOKUP with an NFS version 2 public filehandle.
Note: The first call may not necessarily be a LOOKUP
if the operation is directed at the public filehandle
itself, e.g. a READDIR or READDIRPLUS of the directory
that is associated with the public filehandle.
If the server returns an NFS3ERR_STALE, NFS3ERR_INVAL, or
NFS3ERR_BADHANDLE error, then assume that the server does
not support WebNFS since it does not recognize the public
filehandle. The client must use the server's portmap
service to locate and use the MOUNT protocol to obtain an
initial filehandle for the requested path.
WebNFS clients can benefit by caching information about the
server: whether the server supports TCP connections (if TCP is
supported then the client should cache the TCP connection as
well), which protocol the server supports and whether the server
supports public filehandles. If the server does not support
public filehandles, the client may choose to cache the port
assignment of the MOUNT service as well as previously used
pathnames and their filehandles.
8. Mount Protocol
If the server returns an error to the client that indicates
no support for public filehandles, the client must use the
MOUNT protocol to convert the given pathname to a filehandle.
Version 1 of the MOUNT protocol is described in Appendix A of
RFC 1094 and version 3 in Appendix I of RFC 1813. Version 2
of the MOUNT protocol is identical to version 1 except for
the addition of a procedure MOUNTPROC_PATHCONF which returns
POSIX pathconf information from the server.
At this point the client must already have some indication
as to which version of the NFS protocol is supported on the
server. Since the filehandle format differs between NFS
versions 2 and 3, the client must select the appropriate
version of the MOUNT protocol. MOUNT versions 1 and 2 return
only NFS version 2 filehandles, whereas MOUNT version 3 returns
NFS version 3 filehandles.
Unlike the NFS service, the MOUNT service is not registered on a
well-known port. The client must use the PORTMAP service to
locate the server's MOUNT port before it can transmit a
MOUNTPROC_MNT request to retrieve the filehandle corresponding to
the requested path.
Client Server
------ ------
-------------- MOUNT port ? --------------> Portmapper
<-------------- Port=984 ------------------
------- Filehandle for /export/foo ? ----> Mountd @ port 984
<--------- Filehandle=0xf82455ce0.. ------
NFS servers commonly use a client's successful MOUNTPROC_MNT
request request as an indication that the client has "mounted"
the filesystem and may maintain this information in a file
that lists the filesystems that clients currently have mounted.
This information is removed from the file when the client
transmits an MOUNTPROC_UMNT request. Upon receiving a
successful reply to a MOUNTPROC_MNT request, a WebNFS client
should send a MOUNTPROC_UMNT request to prevent an accumulation
of "mounted" records on the server.
Note that the additional overhead of the PORTMAP and MOUNT
protocols will have an effect on the client's binding time
to the server and the dynamic port assignment of the MOUNT
protocol may preclude easy firewall or proxy server transit.
The client may regain some performance improvement by utilizing
a pathname prefix cache. For instance, if the client already
has a filehandle for the pathname "a/b" then there is a good
chance that the filehandle for "a/b/c" can be recovered by
by a lookup of "c" relative to the filehandle for "a/b",
eliminating the need to have the MOUNT protocol translate
the pathname. However, there are risks in doing this.
Since the LOOKUP response provides no indication of filesystem
mountpoint crossing on the server, the relative LOOKUP may
fail, since NFS requests do not normally cross mountpoints
on the server. The MOUNT service can be relied upon to
evaluate the pathname correctly - including the crossing
of mountpoints where necessary.
9. Exploiting Concurrency
NFS servers are known for their high capacity and their
responsiveness to clients transmitting multiple concurrent
requests. For best performance, a WebNFS client should take
advantage of server concurrency. The RPC protocol on which the NFS
protocol is based, provides transport-independent support for this
concurrency via a unique transaction ID (XID) in every NFS
request.
There is no need for a client to open multiple TCP connections
to transmit concurrent requests. The RPC record marking
protocol allows the client to transmit and receive a stream
of NFS requests and replies over a single connection.
9.1 Read-ahead
To keep the number of READ requests to a minimum, a WebNFS
client should use the maximum transfer size that it and the
server can support. The client can often optimize utilization
of the link bandwidth by transmitting concurrent READ requests.
The optimum number of READ requests needs to be determined
dynamically taking into account the available bandwidth, link
latency, and I/O bandwidth of the client and server, e.g.
the following series of READ requests show a client using
a single read-ahead to transfer a 128k file from the server
with 32k READ requests:
READ XID=77 offset=0 for 32k -->
READ XID=78 offset=32k for 32k -->
<-- Data for XID 77
READ XID=79 offset=64k for 32k -->
<-- Data for XID 78
READ XID=80 offset=96k for 32k -->
<-- Data for XID 79
<-- Data for XID 80
The client must be able to handle the return of data
out of order. For instance, in the above example the
data for XID 78 may be received before the data for XID 77.
The client should be careful not to use read-ahead beyond
the capacity of the server, network, or client, to handle
the data. This might be determined by a heuristic that
measures throughput as the download proceeds.
9.2 Concurrent File Download
A client may combine read-ahead with concurrent download
of multiple files. A practical example is that of Web
pages that contain multiple images, or a Java Applet that
imports multiple class files from the server.
Omitting read-ahead for clarity, the download of multiple
files, "file1", "file2", and "file3" might look something
like this:
LOOKUP XID=77 0x0 "file1" -->
LOOKUP XID=78 0x0 "file2" -->
LOOKUP XID=79 0x0 "file3" -->
<-- FH=0x01 for XID 77
READ XID=80 0x01 offset=0 for 32k -->
<-- FH=0x02 for XID 78
READ XID=81 0x02 offset=0 for 32k -->
<-- FH=0x03 for XID 79
READ XID=82 0x03 offset=0 for 32k -->
<-- Data for XID 80
<-- Data for XID 81
<-- Data for XID 82
Note that the replies may be received in a different order
from the order in which the requests were transmitted. This
is not a problem, since RPC uses the XID to match requests
with replies. A benefit of the request/reply multiplexing
provided by the RPC protocol is that the download of a large
file that requires many READ requests will not delay the
concurrent download of smaller files.
Again, the client must be careful not to drown the server
with download requests.
10.0 Timeout and Retransmission
A WebNFS client should follow the example of conventional
NFS clients and handle server or network outages gracefully.
If a reply is not received within a given timeout, the client
should retransmit the request with its original XID (described
in Section 8 of RFC 1831). The XID can be used by the server
to detect duplicate requests and avoid unnecessary work.
While it would seem that retransmission over a TCP connection
is unnecessary (since TCP is responsible for detecting
and retransmitting lost data), at the RPC layer retransmission
is still required for recovery from a lost TCP connection, perhaps
due to a server crash or, because of resource limitations, the server
has closed the connection. When the TCP connection is lost, the
client must re-establish the connection and retransmit pending
requests.
The client should set the request timeout according to the
following guidelines:
- A timeout that is too small may result in the
wasteful transmission of duplicate requests.
The server may be just slow to respond, either because
it is heavily loaded, or because the link latency is high.
- A timeout that is too large may harm throughput if
the request is lost and the connection is idle waiting
for the retransmission to occur.
- The optimum timeout may vary with the server's
responsiveness over time, and with the congestion
and latency of the network.
- The optimum timeout will vary with the type of NFS
request. For instance, the response to a LOOKUP
request will be received more quickly than the response
to a READ request.
- The timeout should be increased according to an
exponential backoff until a limit is reached.
For instance, if the timeout is 1 second, the
first retransmitted request should have a timeout of
two seconds, the second retransmission 4 seconds, and
so on until the timeout reaches a limit, say 30 seconds.
This avoids flooding the network with retransmission
requests when the server is down, or overloaded.
As a general rule of thumb, the client should start with
a long timeout until the server's responsiveness is determined.
The timeout can then be set to a value that reflects the
server's responsiveness to previous requests.
11.0 Bibliography
[RFC1808] R. Fielding,
"Relative Uniform Resource Locators," RFC-1808,
June 1995
http://www.internic.net/rfc/rfc1808.txt
[RFC1831] R. Srinivasan, "RPC: Remote Procedure Call
Protocol Specification Version 2," RFC-1831,
August 1995.
http://www.internic.net/rfc/rfc1831.txt
[RFC1832] R. Srinivasan, "XDR: External Data Representation
Standard," RFC-1832, August 1995.
http://www.internic.net/rfc/rfc1832.txt
[RFC1833] R. Srinivasan, "Binding Protocols for ONC RPC
Version 2," RFC-1833, August 1995.
http://www.internic.net/rfc/rfc1833.txt
[RFC1094] Sun Microsystems, Inc., "Network Filesystem
Specification," RFC-1094, DDN Network
Information Center, SRI International, Menlo
Park, CA. NFS version 2 protocol
specification.
http://www.internic.net/rfc/rfc1094.txt
[RFC1813] Sun Microsystems, Inc., "NFS Version 3 Protocol
Specification," RFC-1813, DDN Network
Information Center, SRI International, Menlo
Park, CA. NFS version 3 protocol
specification.
http://www.internic.net/rfc/rfc1813.txt
[RFCmmmm] B. Callaghan, "WebNFS Server Specification,"
RFC-mmmm, October 1996.
http://www.internic.net/rfc/rfcmmmm.txt
[Sandberg] Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh,
B. Lyon, "Design and Implementation of the Sun
Network Filesystem," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
Summer 1985. The basic paper describing the
SunOS implementation of the NFS version 2
protocol, and discusses the goals, protocol
specification and trade-offs.
[X/OpenNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: XNFS,
X/Open Company, Ltd., Apex Plaza, Forbury Road,
Reading Berkshire, RG1 1AX, United Kingdom,
1991. This is an indispensable reference for
NFS version 2 protocol and accompanying
protocols, including the Lock Manager and the
Portmapper.
[X/OpenPCNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: (PC)NFS,
Developer's Specification, X/Open Company, Ltd.,
Apex Plaza, Forbury Road, Reading Berkshire, RG1
1AX, United Kingdom, 1991. This is an
indispensable reference for NFS version 2
protocol and accompanying protocols, including
the Lock Manager and the Portmapper.
12. Security Considerations
Since the WebNFS server features are based on NFS protocol
versions 2 and 3, the RPC based security considerations
described in RFC 1094, RFC 1831, and RFC 1832 apply here also.
Clients and servers may separately negotiate secure
connection schemes for authentication, data integrity,
and privacy.
13. Acknowledgements
This specification was extensively reviewed by the NFS
group at SunSoft and brainstormed by Michael Eisler.
14. Author's Address
Address comments related to this document to:
nfs@eng.sun.com
Brent Callaghan
Sun Microsystems, Inc.
2550 Garcia Avenue
Mailstop Mpk17-201
Mountain View, CA 94043-1100
Phone: 1-415-786-5067
Email: brent.callaghan@eng.sun.com
Fax: 1-415-786-5896