Libguestfs provides ways to enumerate guest storage (eg. partitions,
LVs, what filesystem is in each LV, etc.). It can also run commands
-in the context of the guest. Also you can access filesystems over FTP.
+in the context of the guest. Also you can access filesystems over
+FUSE.
Libguestfs is a library that can be linked with C and C++ management
programs (or management programs written in OCaml, Perl, Python, Ruby,
=back
+=head2 PROTOCOL LIMITS
+
+Internally libguestfs uses a message-based protocol to pass API calls
+and their responses to and from a small "appliance" (see L</INTERNALS>
+for plenty more detail about this). The maximum message size used by
+the protocol is slightly less than 4 MB. For some API calls you may
+need to be aware of this limit. The API calls which may be affected
+are individually documented, with a link back to this section of the
+documentation.
+
+A simple call such as C<guestfs_cat> returns its result (the file
+data) in a simple string. Because this string is at some point
+internally encoded as a message, the maximum size that it can return
+is slightly under 4 MB. If the requested file is larger than this
+then you will get an error.
+
+In order to transfer large files into and out of the guest filesystem,
+you need to use particular calls that support this. The sections
+L</UPLOADING> and L</DOWNLOADING> document how to do this.
+
+You might also consider mounting the disk image using our FUSE
+filesystem support (L<guestmount(1)>).
+
=head1 CONNECTION MANAGEMENT
=head2 guestfs_h *