The server responds to every command with a status code, often with an appended explanatory text. However,
most commands are only permitted after successful authentication.
HEC
Header Error Check is a checking method used in the Asynchronous Transfer Mode (ATM) transmission
technique that determines whether an ATM cell was properly received. In this method, the header of the ATM
cell contains a header error code (HEC) in the fifth and last byte and this code corresponds to a Frame Check
Sequence (FCS). It handles errors in the cell header, but it chiefly checks if the cell boundaries were correctly
identified in the received bit stream. During reception, the receiver continuously calculates the expected HEC
byte and compares it with the byte that it receives. If the two values do not agree, it first corrects the cell header
when it relays the cell. After a few sequential errors, the receiver assumes that it has lost synchronization and
restarts synchronizing the receiver. This is why ATM is termed asynchronous. It allows a much greater
deviation of the synchronization of network elements than possible with PDH. This solution in ATM targets the
integration of data traffic that, in contrast to the telephone networks that are centrally clocked with high
accuracy, may come from the completely unsynchronized sources of private users.
Hop
The Hop Count is the number of steps that a packet must take on the path from the source to the destination;
the number of routers lying along this path is logically one less. The Hop Count can be determined, for example,
using the Traceroute diagnostic tool. The Time to Live approach in which a counter variable in the data packet
itself is decremented by one with each hop is based on hops. If the counter variable reaches a value of zero, the
packet is discarded, thus not relayed any further and deleted. This prevents data packets from wandering
forever throughout the network and wasting resources if circular routes are formed due to faulty routing.
HTTP
The Hypertext Transfer Protocol (HTTP) is a protocol for transferring data over a network. It is mainly used to
load websites from the World Wide Web (WWW) into a web browser. HTTP is one of the application-layer-
established network models. The application layer is addressed by the application programs and, in the case of
HTTP, this is usually a web browser. In the ISO/OSI layer model, the application layer corresponds to layers
5–7.
IPoA (IP over ATM)
IP over ATM (IPoA) or, more precisely, IP and ARP over ATM, is a transmission technique in which various
protocols can be combined with one another. This is the IP protocol with the Address Resolution Protocol
(ARP) transmitted via ATM. In this technique that is not standardized and is described in RFC 1577 from 1994,
the communication partners must have an ATM address and an IP address. The ATM network serves as the
transmission network between the communication partners. Logical IP Subnets (LISs) that behave just like IP
subnets are built on the ATM network. The ARP protocol is used for converting IP addresses into ATM
addresses.
IPTV
Internet Protocol Television (IPTV) generally identifies the Internet transmission path for television programs
and films in contrast to classic radio, cable or satellite. IPTV is neither a standard nor a concept and is thus only
a generic term that can be found in very many different forms. The different forms extend from simple IPTV,
computers or cellular telephones all the way to special terminals where the user does not even notice that he is
using the Internet because he operates a set-top box by way of the television set.
Interleaving
This is used when communicating between an (A)DSL modem and the exchange. It ensures a high level of
data security even when there are line disturbances by transmitting data packets in an altered sequence in a
"zipper" procedure. Noise is thereby recognized and eliminated by the exchange. The speed of data
transmission is not influenced by the interleaving procedure per se, but unfortunately the PING is poorer which
is disadvantageous for online games, IPTV and VOIP: Interleaving increases the response times by a factor of
2 since the path on which interleaving occurs is traversed twice. The higher the time factor, the more errors can
occur. The smaller the time factor, the shorter the response times. Interleaving is not used in fastpath mode.
Operating Manual
KE3500
xDSL
M
ULTI
T
EST
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