To be pedantic, the IMR provides
object-key → IOR mappings. However, the object
key used is part of an IOR that contained the IMR’s host and
port, so conceptually the IMR provides
IOR → IOR mappings.
A firewall is a part of security infrastructure that
prevents malicious hackers on the Internet from
accessing the computers inside an organization’s
network. A firewall blocks most TCP/IP
traffic from outside the organization’s network, but
can be configured to allow traffic on a set of fixed
ports. In this way,
the firewall can be configured to allow external access
to a small number of services that are inside the
organization’s network; typical examples include FTP,
telnet and/or a web server. A typical requirement for
exposing an internal service through a firewall is that
the service listen on a fixed port .