CIR – Committed Information Rate
a specified amount of guaranteed bandwidth (measured in bits per second) on a Frame Relay service
Local Access Rate
clock speed of theconnection CPE or last mile loop to the service providers frame switch, rate of speed that packets travel
VC Virtual Circuit
bi-directional path between network devices
PVC/SVW – Permanent Virtual Circuit / Switched Virtual Circuit
a permanently or switch circuit between a router and a frame-relay switch. when it is a switched path, it is established on-demand and torn down, when the transfer is complete. I it similar to an ISDN circuit.
A PVC is up all the time.
DLCI – Data Link Connection Identifier
assigned by the service provider. This number is used to identify the logical link between the router (DTE) and the frame relay switch (DCE). DLCI’s are only localy significant as they are only valid between the router and the frame-relay switch.
LMI – Logical Management Interface
Types: Ansi, Cisco, Q933a
it’s a signaling standard between the router and the service providers frame-relay switch. It manages the connection and maintains the status between devices. LMI messages will be send back and forth between the router and the switch. The status of the link can be:
Active
inactive
deleted
it is a good idea to „debug frame-relay lmi“ to troubleshoot a connection.
Point-to-Point Connection
– talk only to one device
Multipoint Connection
– to more than one device
FECN – Forward Explicit Congestion Notification
sending FECN Packet if noticed congestion on the network
BECN – Backward Explicit Congestio Notification
if the frame-relay switch noticed congestion it send’s a BECN Packet
Keepalive
every 10 secound a keepalive is sent by the router. If no keepalive arrives, the link is assumed to be down.
usefull debug explanation for „debug frame-relay lm“
PVC information element, length, dlci, status, CIR in decimal, for PVC Status
Could be:
0x00 = added/inactive
the remote end is not able to receive traffic at this time
0x02 = added/active
both ends are up
0x04 = deleted
the end router is no longer receiving LMI from the CO
0x08 = new/inactive
0x0a = new/active