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– A routing table entry that is used to direct packets addressed to networks not explicitly listed in
Default Route
the routing table.
DES (Data Encryption Standard)
NIST standard for a secret key cryptography method that uses a 56-bit key.
Destination Port Number ZZZZ
consists of the pair of IP addresses that are talking to each other, as well a pair of port numbers. The
destination port number often indicates the type of service being connected to. When a firewall blocks a
connection, it will save the destination port number to its logfile.
Port numbers are divided into three ranges:
•
The Well-Known Ports are those from 0 through 1023. These are tightly bound to services, and usually
traffic on this port clearly indicates the protocol for that service. For example, port 80 virtually always
indicates HTTP traffic.
•
The Registered Ports are those from 1024 through 49151. These are loosely bound to services, which
means that while there are numerous services "bound" to these ports, these ports are likewise used for
many other purposes. For example, most systems start handing out dynamic ports starting around 1024.
•
The Dynamic and/or Private Ports are those from 49152 through 65535. In theory, no service should be
assigned to these ports.
DHCP (Dynamic Host Configuration Protocol)
a pool of IP addresses, allowing a smaller number of addresses to serve a much larger number of users.
– The encryption of a message digest with a private key. Digital signatures are based on
Digital Signature
public-key cryptography, which was first introduced by Whitfield Diffie and Martin Hellman of Stanford
University in 1976. Until 1976 there was only conventional cryptography, which uses the same key to both
scramble (encrypt) and unscramble (decrypt) information. Public key cryptography is based on two keys, a
private key and a public key.
Where conventional cryptography is a one-key system for both locking (encrypting) and unlocking (decrypting)
a message, public key cryptography uses different keys for locking and unlocking.
In public-key systems, one key can be kept private while the other key is made public. Knowing the public key
does not reveal the private key.
DNAT (Dynamic NAT)
only run there available to the Internet.
The use of private IP addresses in combination with Network Address Translation (NAT) in the form of
Masquerading, Source NAT (SNAT), and Destination NAT (DNAT) allows a whole network to hide behind one
or a few IP addresses preventing the identification of your network topology from the outside. With these
mechanisms, Internet connectivity remains available, while it is no longer possible to identify individual
machines from the outside. By using Destination NAT (DNAT), it is still possible to place servers within the
protected network/DMZ and make them available for a certain service.
In DNAT, only the IP address – not the port – is translated. Typically, the number of externally visible IP
addresses is less than the number being hidden behind the NAT router.
DNS (Domain Name System) (also Domain Name Service)
aliases instead of having to use computer-friendly IP addresses. Name servers take care of the conversion
from number to name. Every institution connected to the Internet must operate at least two independent name
servers that can give information about its names and numbers. Additionally, there is a name server for every
top-level domain that lists all the subordinate name servers of that domain. Thus the Domain Name System
represents a distributed hierarchical database. Normally, however, the database is not accessed by the user
him-/herself, but by the network application that he/she is presently working with.
DDoS (Distributed Denial of Service)
designed as a coordinated attack from many sources simultaneously against one or more targets. See also
"DoS attacks".
DoS (Denial of Service) attacks
target systems inoperable and/or render target networks inaccessible. DoS attacks typically generate a large
amount of traffic from a given host or subnet and it's possible for a site to detect such an attack in progress and
defend themselves. See also "Distributed DoS attacks".
– The technique used by layered protocols in which a layer adds header information to the
Encapsulation
protocol data unit (PDU) from the layer above. For example, in Internet terminology, a packet would contain a
MultiAccess Communications Server MA30120 User Guide
– A secret key encryption scheme; contrast with "public key". DES is an
– All the traffic going through the firewall is part of a connection. A connection
– Used to operate a private network behind a firewall and make network services that
– Attacks are a nefarious extension of DoS attacks because they are
– A major concern to the Internet community because they attempt to render
– An IETF standard for dynamically allocating and managing
– Refers to the more user-friendly names, or
Glossary
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