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Q128985: INFO: Comparing SNA client TCP/IP named pipes vs sockets

Article: Q128985
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.1,2.11,3.0,4.0
Operating System(s): 
Keyword(s): kbinterop kbnetwork sna4
Last Modified: 13-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 2.1, 2.11, 3.0, 4.0 
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SUMMARY
=======

The TCP/IP windows sockets interface was added in SNA Server 2.1 and is
configured during SNA Server client setup:

- Microsoft Networking (named pipes)

- Novell Netware (native IPX/SPX)

- Banyan VINES (through Banyan IP)

- TCP/IP (through windows sockets)

When the Microsoft TCP/IP protocol is installed onto a Windows 3.1, Windows for
Workgroups 3.11, Windows 95 or Windows NT computer, the SNA Server client can
communicate to the server over:

- Microsoft Networking (named pipes over TCP/IP)

  -or-

- TCP/IP (over the Windows sockets interface)

The TCP/IP windows sockets interface was added to SNA Server 2.1 and is the
recommended SNA Server client connection method for customers using the TCP/IP
transport. NOTE: To use TCP/IP sockets, the SNA Server client software requires
that the TCP/IP transport support the Windows Sockets version 1.1 specification.
TCP/IP sockets provides better performance and better reliability when
connecting to servers across routed IP networks.

This article compares these two methods of connecting from an SNA Server client.

MORE INFORMATION
================

Named Pipes over TCP/IP
-----------------------

When communicating over named pipes, the SNA Server client opens a named pipe
resource (\\server\PIPE\...) which is created by the SNA Server. A named pipe is
an interprocess communication facility supported by the client redirector (that
is, Windows for Workgroups protected mode redirector) and the Windows NT Server.
The SNA Server client and server send messages to each other over this named
pipe.

As with shared file and printer connections, named pipe session traffic flows
over a NetBIOS session between the client redirector and the Windows NT server
using the "Server Message Block" (SMB) protocol. The following illustrates the
message flow:

    SNA Client         <- Named Pipe ->           SNA Server

    Redirector   <- SMB over NetBIOS session ->   NT Server

    TCP/IP          <- TCP/IP connection ->       TCP/IP

    Network card <---------------------------->   Network card

A typical message packet would include the following information:

     [ IP | TCP [ NetBios [ SMB ( SNA application data ) ] ] ]

Disadvantages of Using Named Pipes
----------------------------------

The client redirector and Windows NT server process all messages passed between
the SNA Server client and the server. All named pipe messages are formatted
within "SMB" requests by the client redirector and NT server which flow over a
NetBios session.

Each NetBios session requires "keep-alive" messages to flow between the client
redirector and Windows NT server. These NetBIOS level acknowledgments lead to
network overhead, and the possibility of NetBIOS-level timeout conditions when
traveling across a routed IP network.

A NetBIOS session over TCP/IP requires NetBIOS-to-IP address name resolution,
requiring a client LMHOSTS file entry for each server, or a WINS server to
provide this name resolution. DNS servers don't provide this name resolution.

Since each SNA Server client has one outstanding read request pending on the
sponsor connection, and one read pending on the SNA application session, Windows
NT server resources are required to handle these pending I/O requests even when
the SNA client session is idle.

Advantages of Using Named Pipes
-------------------------------

Windows NT user validation is performed by the client redirector and the Windows
NT server (as part of the SMB protocol). This allows the user's initial network
login to be used.

TCP/IP Sockets
--------------

When communicating over TCP/IP sockets, the SNA Server client opens a TCP/IP
socket number created by the SNA Server. A socket is a session- oriented
interprocess communication facility supported directly over the TCP/IP
transport. The following illustrates the message flow:

    SNA Client         <- TCP/IP socket ->         SNA Server

    TCP/IP           <- TCP/IP connection ->       TCP/IP

    Network card  <---------------------------->   Network card

A typical message packet includes the following information:

     [ IP | TCP ( SNA application data ) ]

Advantages of Using TCP/IP Sockets
----------------------------------

The SNA Server client and server communicate directly over the Windows sockets
interface, bypassing NetBIOS, the SMB protocol, and overhead introduced using
the named pipes interface.

TCP/IP name-to-IP address resolution is provided by the client HOSTS file, DNS
server, or WINS server

TCP/IP session keep-alive timeout processing is handled directly by the SNA
Server client and server. The SNA Server WatchDogTimeOut setting controls the
timeout value, as described in the SNA Server 2.1 readme file (the default is 60
seconds).

The SNA Server Win 3.x client uses a larger buffer size to exchange data with the
server than does the SNA client named pipe interface. Also, data transfer is
performed using byte stream protocol which makes better use of network resources
(named pipes uses message mode protocol).


Disadvantages of Using TCP/IP Sockets
-------------------------------------

User authentication is handled by the SNA Server client and server. This requires
the user to "login" to the Windows NT network when the SNA client software is
loaded. This client login can be automated to some degree, as described on page
208 of the SNA Server 2.1 Reference Guide. In SNA Server 2.11, more enhancements
have been made in this area. For additional information, see the following
article in the Microsoft Knowledge Base:

  Q130854 TITLE :Automating the SNA Server Win 3.x Client Login Process

NOTE: Windows 95 and Windows NT support secure programmatic methods to
impersonate the currently logged on user. Therefore, there is no need to
automate the client logon request when using the SNA Server Windows 95 or
Windows NT client software.

Additional query words: prodsna tcp/ip sockets named pipes snafaq

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Keywords          : kbinterop kbnetwork sna4 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ211 kbSNAServ400 kbSNAServ210
Version           : WINDOWS:2.1,2.11,3.0,4.0
Issue type        : kbinfo

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