Specifications

134 AVM Access Server – Glossary
router becoming unavailable, for example), it forwards this information
to the surrounding routers. Furthermore, a RIP router sends broadcasts
at regular intervals to publish its entire database of routing informa-
tion. These broadcasts ensure that all routers in the internetwork are
synchronized.
Route
A route is the path traveled by a data packet through the network from
its source to its destination. A return route is also necessary in order for
the receiver to send a response.
Short-Hold Mode
Short-Hold Mode refers to the physical interruption of idle ISDN con-
nections after a specified delay. The ISDN link incurs connection charg-
es whenever a B channel is connected, regardless of whether data is
actually being transported or not. Because an ISDN connection can be
dialed up very quickly (in 1 to 2 seconds), it makes sense to clear down
the physical ISDN connection temporarily when no data is sent for a
certain time. The logical ISDN connection is maintained in accordance
with the configuration settings. As soon as new data is queued for
transmission, the physical connection is dialed up again in the back-
ground. This mechanism is transparent to the network user.
SMTP (Simple Mail Transfer Protocol)
SMTP is a standard protocol for exchanging e-mail between computers.
SMTP implementations listen on TCP port 25. The protocol structure is
simple, supporting only e-mail transmission over a data network. SMTP
is defined in RFC 821.
Spoofing
“Spoofing” in data communication means to send data with a false
source address, pretending to be from a different system.
Several network applications are known to exchange data packets that
can cause frequent, unnecessary physical connections when operated
over ISDN WAN links. Some packet types, in particular those used by
Windows file and printer sharing, require acknowledgement from the re-
mote system. The AVM Access Server cannot simply filter such packets
out of the data stream going over the ISDN link, since without the re-
sponse the server would consider the client application to be inactive.