Frame Relay network encapsulated within a Frame Relay frame. It
will add the DLCI number associated with the serial interface. DLCIs
identify the virtual circuit (PVC or SVC) to the routers and provider's
switches participating in the Frame Relay network.
tal signal and encodes it into the type of digital signaling that the switch
at the packet switching exchange (PSE) can understand. The PSE receives
the digital signal and extracts the ones and zeros from the line.
service provider, and its location is the service provider's first point of
responsibility (last point on the receiving end). The demarc is typically
just an RJ-45 jack installed close to the router and CSU/DSU.
loop. The local loop connects to the closest central office (CO), some-
times called a point of presence (POP). The local loop can connect using
various physical mediums, but twisted-pair or fiber is very common.
"cloud" to its destination. This cloud can be dozens of switching
offices--or more! It looks for the destination DLCI address based on
the local DLCI number the frame was transmitted from. It typically
can find the DLCI number of the remote device or router by looking
up a DLCI mapping created by the service provider. Frame Relay map-
pings are usually created statically by the service provider, but they
can be created dynamically using the Inverse ARP (IARP) protocol.
Remember that before data is sent through the cloud, the virtual cir-
cuit is created from end to end.
office, it is sent through the local loop. The frame is received at the
demarc and then is sent to the CSU/DSU. Finally, the router extracts
the packet, or datagram, from the frame and puts the packet in a