I just had a discussion on our Linux Fast Path (LFP) function and looked for additional material to our z/VSE documentation.
May be the article (see link below) is also of interest for you.
Besides the two TCP/IP stacks we also provide a function that bypasses the TCP/IP stack on z/VSE - or doesn't require one.
This function is called Linux Fast Path - or short LFP. A TCP/IP application on z/VSE can communicate with a LFP daemon (small program)
running on Linux on z Systems. The daemon communicates through the Linux TCP/IP stack with the network.
LFP may communicate between LPARs or z/VM guests. A Linux instance (distribution) is required.
The z114, z196, zBC12, zEC12 and z13 processors also provide a feature called z/VSE z/VM IP Assist (VIA),
that can be exploited by LFP. With VIA the processor provides the functionality to communicate to the network without having a Linux distribution installed.
I just found a good z/Journal article from 2011 describing the LFP function.
The article is here.