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| author | William Joye <wjoye@cfa.harvard.edu> | 2018-01-23 16:53:51 (GMT) |
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| committer | William Joye <wjoye@cfa.harvard.edu> | 2018-01-23 16:53:51 (GMT) |
| commit | 51e1f85047b34f095ed69a3024d696997d2667c8 (patch) | |
| tree | a8d46838982aa78a35653c10d0b7370d751d6181 /xpa/doc/inet.html | |
| parent | 0c198f7902ee997dd8ec3631e8ff1c385257014d (diff) | |
| download | blt-51e1f85047b34f095ed69a3024d696997d2667c8.zip blt-51e1f85047b34f095ed69a3024d696997d2667c8.tar.gz blt-51e1f85047b34f095ed69a3024d696997d2667c8.tar.bz2 | |
upgrade xpa
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| -rw-r--r-- | xpa/doc/inet.html | 260 |
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diff --git a/xpa/doc/inet.html b/xpa/doc/inet.html deleted file mode 100644 index 3155885..0000000 --- a/xpa/doc/inet.html +++ /dev/null @@ -1,260 +0,0 @@ -<!-- =defdoc xpainet xpainet n --> -<HTML> -<HEAD> -<TITLE>XPA Communication Between Hosts</TITLE> -</HEAD> -<BODY> - -<!-- =section xpainet NAME --> -<H2><A NAME="xpainet">XPAInet: XPA Communication Between Hosts</A></H2> - -<!-- =section xpainet SYNOPSIS --> -<H2>Summary</H2> -XPA uses standard inet sockets to support communication between two or -more host computers. - -<!-- =section xpainet DESCRIPTION --> -<H2>Description</H2> -<P> -When the <A HREF="./method.html">Communication Method</A> is set to -<B>inet</B> (as it is by default), XPA can be used to communicate -between different computers on the Internet. INET sockets utilize the -IP address of the given machine and a (usually random) port number to -communicate between processes on the same machine or between different -machines on the Internet. These standard Internet sockets are also -used by programs such as Netscape, ftp. etc. - -<P> -XPA supports a host-based <A HREF="./acl.html">Access Control</A> mechanism -to prevent unauthorized access of XPA access points by other computers -on the Net. By default, only the machine on which the XPA server is -running can access XPA services. Therefore, setting up communication -between a local XPA server machine and a remote client machine -requires a two-part registration process: - -<UL> -<LI> the XPA service on the local machine must be made known to the -remote machine -<LI> the remote machine must be given permission to access the local -XPA service -</UL> - -Three methods by which this remote registration can be accomplished -are described below. - -<H2>Manual Registration</H2> - -The first method is the most basic and does not require the remote -client to have xpans running. To use it, the local server simply -gives a remote client machine access to one or more XPA access points -using xpaset and the <B>-acl</B> sub-command. For example, -consider the XPA test program "stest" running on a local machine. By -default the access control for the access point named "xpa" is -restricted to that machine: -<PRE> - [sh]$ xpaget xpa -acl - *:* 123.456.78.910 gisa - *:* localhost gisa -</PRE> -Using xpaset and the <B>-acl</B> sub-command, a remote client -machine can be given permission to perform xpaget, xpaset, xpaaccess, -or xpainfo operations. For example, to allow the xpaget operation, the -following command can be issued on the local machine: -<PRE> - [sh]$ xpaset -p xpa -acl "remote_machine g" -</PRE> -This results in the following access permissions on the local machine: -<PRE> - [sh]$ xpaget xpa -acl - XPA:xpa 234.567.89.012 g - *:* 123.456.78.910 gisa - *:* localhost gisa -</PRE> - -The remote client can now use the local server's xpans name server to -establish communication with the local XPA service. This can be done -on a call-by-call basis using the <B>-i</B> switch on xpaset, xpaget, etc: -<PRE> - [sh]$ xpaget -i "local_machine:12345" xpa - class: XPA - name: xpa - method: 88877766:2778 - sendian: little - cendian: big -</PRE> -Alternatively, the XPA_NSINET variable on the remote machine can be -set to point directly to xpans on the local machine, removing -the need to override this value each time an XPA program is run: -<PRE> - [csh]$ setenv XPA_NSINET 'karapet:$port' - [csh]$ xpaget xpa - class: XPA - name: xpa - method: 88877766:2778 - sendian: little - cendian: big -</PRE> -Here, '$port' means to use the default XPA name service port (14285). -not a port environment variable. - -<p> -Access permission for remote client machines can be stored in a file -on the local machine pointed to by the <B>XPA_ACLFILE</B> environment -variable or using the <B>XPA_DEFACL</B> environment variable. See <A -HREF="./acl.html">XPA Access Control</A> for more information. - -<H2>Remote Registration</H2> - -If xpans is running on the remote client machine, then a local xpaset -command can be used with the <B>-remote</B> sub-command to -register the local XPA service in the remote name service, while at -the same time giving the remote machine permission to access the local -service. For example, assume again that "stest" is running on the -local machine and that xpans is also running on the remote machine. -To register access of this local xpa on the remote machine, use -the xpaset and the <B>-remote</B> sub-command: -<PRE> - [sh]$ ./xpaset -p xpa -remote 'remote_machine:$port' + -</PRE> -To register the local xpa access point on the remote machine with xpaget -access only, execute: -<PRE> - [sh]$ ./xpaset -p xpa -remote 'remote_machine:$port' g -</PRE> -Once the remote registration command is executed, the remote client -machine will have an entry such as the following in its own xpans name -service: -<PRE> - [csh]$ xpaget xpans - XPA xpa gs 88877766:2839 eric -</PRE> -The xpa access point can now be utilized on the remote machine without -further setup: -<PRE> - [csh]$ xpaget xpa - class: XPA - name: xpa - method: 838e2f68:2839 - sendian: little - cendian: big -</PRE> -To unregister remote access from the local machine, use the same -command but with a '-' argument: -<PRE> - [sh]$ xpaset -p xpa -remote 'remote_machine:$port' - -</PRE> -The benefit of using remote registration is that communication with -remote access points can be mixed with that of other access points -on the remote machine. Using <A HREF="./template.html">Access Point -Names and Templates</A>, one XPA command can be used to send or -receive messages to the remote and local services. - -<H2>XPANS Proxy Registration</H2> - -The two methods described above are useful when the local and remote -machines are able to communicate freely to one another. This would be -the case on most Local Area Networks (LANs) where all machines are -behind the same firewall and there is no port blocking between -machines on the same LAN. The situation is more complicated when the -XPA server is behind a firewall, where outgoing connections are -allowed, but incoming port blocking is implemented to prevent machines -outside the firewall from connecting to machines inside the -firewall. Such incoming port blocking will prevent xpaset and xpaget -from connecting to an XPA server inside a firewall. - -<P> -To allow locally fire-walled XPA services to register with remote -machines, we have implemented a proxy service within the xpans name -server. To register remote proxy service, xpaset and the -<B>-remote</B> sub-command is again used, but with an additional -<B>-proxy</B> argument added to the end of the command: -<PRE> - [sh]$ ./xpaset -p xpa -remote 'remote_machine:$port' g -proxy -</PRE> -Once a remote proxy registration command is executed, the remote -machine will have an entry such as the following in its own xpans name -service: -<PRE> - [csh]$ xpaget xpans - XPA xpa gs @88877766:2839 eric -</PRE> -The '@' sign in the name service entry indicates that xpans proxy -processing is being used for this access point. Other than that, from -the user's point of view, there is no difference in how this XPA -access point is contacted using XPA programs (xpaset, xpaget, etc.) or -libraries: -<PRE> - [csh]$ xpaget xpa - class: XPA - name: xpa - method: 88877766:3053 - sendian: little - cendian: big -</PRE> -<P> -Of course, the underlying processing of the XPA requests is very much -different when xpans proxy is involved. Instead of an XPA program such -contacting the XPA service directly, it contacts the local xpans. -Acting as a proxy server, xpans communicates with the XPA service -using the command channel established at registration time. Commands -(including establishing a new data channel) are sent between xpans and -the XPA service to set up a new message transfer, and then data is fed -to/from the xpa request, through xpans, from/to the XPA service. In -this way, it can be arranged so that connections between the -fire-walled XPA service and the remote client are always initiated by -the XPA service itself. Thus, incoming connections that would be -blocked by the firewall are avoided. Note that there is a performance -penalty for using the xpans/proxy service. Aside from extra overhead -to set up proxy communication, all data must be sent through the -intermediate proxy process. - -<P> -The xpans proxy scheme requires that the remote client allow the local -XPA server machine to connect to the remote xpans/proxy server. If the -remote client machine also is behind a port-blocking firewall, such -connections will be disallowed. In this case, the only solution is to -open up some ports on the remote client machine to allow incoming -connections to xpans/proxy. Two ports must be opened (for command and -data channel connections). By default, these two ports are 14285 and -14287. The port numbers can be changed using the <B>XPA_NSINET</B> -environment variable. This variable takes the form: -<PRE> - setenv XPA_NSINET machine:port1[,port2[,port3]] -</PRE> -where port1 is the main connecting port, port2 is the XPA access port, -and port3 is the secondary data connecting port. The second and third -ports are optional and default to port1+1 and port1+2, respectively. -It is port1 and port3 that must be left open for incoming connections. - -<P> -For example, to change the port assignments so that xpans listens -for registration commands on port 12345 and data commands on port 28573: -<PRE> - setenv XPA_NSINET myhost:12345 -</PRE> -Alternatively, all three ports can be assigned explicitly: -<PRE> - setenv XPA_NSINET remote:12345,3000,12346 -</PRE> -In this case 12345 and 12346 should be open for incoming connections. -The XPA access port (which need not be open to the outside -world) is set to 3000. - -<P> -Finally, note that we currently have no mechanism to cope with -Internet proxy servers (such as SOCKS servers). If an XPA service is -running on a machine that cannot connect directly to outside machines, -but goes through a proxy server instead, there currently is no way to -register that XPA service with a remote machine. We hope to implement -support for SOCKS proxy in a future release. - -<!-- =section xpainet SEE ALSO --> -<!-- =text See xpa(n) for a list of XPA help pages --> -<!-- =stop --> - -<P> -<A HREF="./help.html">Go to XPA Help Index</A> - -<H5>Last updated: September 10, 2003</H5> -</BODY> -</HTML> |