tainy hmod-v3-io, tainy hmod-l3-io - Dr. Neuhaus ...

IPsec
MIB See SNMP
Small lexicon of routers
IP security (IPsec) is a standard which uses IP datagrams to ensure the
authenticity of the sender, the confidentiality and the integrity of the data
through encryption. The components of IPSec are the authentication Header
(AH), the encapsulating security payload (ESP), the security association
(SA), the security parameter index (SPI) and the internet key exchange (IKE).
At the beginning of the communication, the computers participating in the
communication clarify the process used and its implications, such as
transport mode or tunnel mode.
In transport mode, an IPSec header is used between the IP header and TCP
or UDP header in each IP datagram. Since the IP header remains
unchanged in the process, this mode is only suitable for a host-to-host
connection.
In tunnel mode, an IPSec header and a new IP header precede the entire IP
datagram. That means the original datagram is encrypted in the payload of
the new datagram.
Tunnel mode is used with the APN: The devices at the tunnel ends encrypt
and decrypt the datagrams along the stretch of the tunnel; in other words,
the actual datagrams are fully protected along the transport route through
the public network.
NAT (Network With network address translation (NAT), often called IP masquerading, an
Address Translation) entire network is "hidden" behind a single device, known as the NAT router.
The internal computers in the local network remain concealed with their IP
addresses in the local network when they communicate outwardly through
the NAT router. Only the ANT router with its own IP address is visible to
outside communication partners.
However, in order for internal computers to be able to communicate directly
with external computers (on the internet), the NAT router must change the IP
datagrams to and from the internal computer to the outside.
If an IP datagram is sent from the internal network to the outside, the NAT
router changes the IP and TCP header of the datagram. It switches the
source IP address and the source port with its own official IP address and its
own, previously unused port. For this purpose, it maintains a table which
establishes the allocation of the original with the new values.
Upon receiving a response datagram, the NAT router recognises that the
datagram is actually intended for an internal computer on the basis of the
specified target port. Using the table, the NAT router exchanges the target IP
address and the target port and forwards the datagram to the internal
network.
TAINY xMOD Page 101 of 111