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Learning About the User Interfaces 31
Frame Relay Requires an address called a Data Link Connection Identifier (DLCI).
DLCIs are assigned by the appropriate authority at subscription
time. A DLCI follows an at sign (@) and can range from 1 through
1022 decimal. The DLCI identifies a virtual circuit on the Frame
Relay network, and is used by the local bridge/router to send a
packet to a router on the other end of the circuit. The following is
an example of a Frame Relay address:
@22
In the standard (local) addressing convention, the DLCI number has
only local significance; a duplicate number can be used by other
bridge/router or tunnel switches. In the global addressing
convention, identifiers used throughout the Frame Relay network
are unique, and all traffic to a node has the same destination DLCI
number.
ATM Consists of an 8-bit virtual path identifier (VPI) and a 16-bit virtual
circuit identifier (VCI), usually represented in VPI.VCI format, where
VPI is a decimal number between 0 and 255 and VCI is a decimal
number between 0 and 65,535. The following is an example of an
Asynchronous Transfer Mode (ATM) address:
107.44
Some vendors’ DSUs require an ATM address that consists of a 0-bit
VPI and a 10-bit VCI. In this case, the 10-bit VCI maps directly to a
Frame Relay DLCI.
SMDS There are two types of Switched Multimegabit Data Service (SMDS)
addresses: individual addresses, for unicast traffic, and group
addresses, for multicast traffic. An individual address routes data to
a unique node. Packets sent to a group address are delivered to all
nodes that share that address. Both types of address begin with a
dollar sign. They are distinguished by the first or control digit:
hexadecimal C for an individual address and hexadecimal E for a
group address. Each address has 15 decimal digits following the
control digit and resembles a telephone number. The software
automatically right-pads shorter addresses with hexadecimal F to
the full length. The following are examples of individual and group
SMDS addresses:
C14085551212FFFF Individual Address
E14085551234FFFF Group Address
X.25 Consists of up to 15 decimal digits and can vary in length. The
address looks similar to a telephone number and is preceded by a
pound sign (#). An X.25 address is also referred to as a data
terminal equipment (DTE) address.
When a device is attached to a public data network (PDN), the
network provider assigns it an X.25 address or an international data
number (IDN). The first four digits indicate the country and PDN to
which the device is attached. The remaining digits represent a
unique device address determined by the network provider. The
following is an example of an X.25 address:
#311041503333