what is the difference between pbx & vnetd?

[Mehul_Pal]

what is the difference between pbx & vnetd?

why we started using pbx instead of vnetd

[sdo]

Using VxPBX means less TCP ports have to be used, therefore less TCP ports open across a firewall, therefore easier to manage:

http://securityresponse.symantec.com/norton/security_response/glossary/define.jsp?letter=v&word=vxpb...

The link above refers to CommandCentral which appears to be another application which also utilises VxPBX.  And so below, I have copied the text/topic from the above link, and changed CC to refer to NetBackup, for clarity...

.

Q:  What is VxPBX?

A:  VxPBX is a common VERITAS component that uses socket passing to reduce the number of ports required to be open across a firewall.  VxPBX uses a paradigm similar to that of a telephone switchboard in which calls placed to a switchboard are redirected to a known extension.  In the "VxPBX exchange", client connections sent to the (VxPBX) exchange's port (i.e. TCP/1556) are redirected to another component within the NetBackup application.

[Marianne · Accepted solution]

NBU port connections have come a long way over many years.

Initially there were a whole bunch of outgoing port numbers and even longer list of connect-back ports.
Server - Client connections was going out on bpcd and connect-back on ports 512 - 1023.

vnetd was introduced in NBU 4.5FP3.
Here server - client connection was going out on bpcd and connect-back on vnetd.

Since NBU 6.0, server - client comms were only using vnetd.
6.0 also introduced single EMM database in environment and master - media server comms started using PBX for EMM comms.

As from 7.0.1, NBU started to use port 1556 (PBX) for server - client comms as well. 

Single comms port makes firewall config a lot easier. 

[sdo]

@Mehul_Pal, I've editted my initial response to include a copy of most of the text from the original link, but I have also updated the copied text, a little bit, to clarify that we're talking about VxPBX in context of NetBackup.

Anyway, the important point above is that of "socket passing".  It is commonly known that one of the most resource expensive events in TCP/IP activity is that of socket instantiation, and socket destruction.  E.g. this is why sockets can have a "keep alive" "close wait", so that they can be re-used after closure but before destruction.  VxPBX extends this idea of TCP/IP efficiency by not having to close a VxPBX socket and open another (bpbkar, bptm, bpbrm, etc) socket - by instead passing the already open socket to another NetBackup process (bpbkar, bptm, bpbrm, etc).

[mph999]

PBX is like a telephone exchange, or as I like to describe it as a dating service.

For example, say bptm wants to talk to nbjm.

The connection goes via PBX, Mr. bptm 'calls' PBX, who accepts the connection, and then introduces Mr. bptm to Miss. nbjm ...