Frame Relay Address Mapping; Frame Relay Terminologies - 3Com MSR 50 Series Configuration Manual

Frame Relay Address
Mapping
A DTE sends a Status-Enquiry message at a certain interval to query the link status.
The DCE responds with a Status response message upon receiving the message. If
the DTE does not receive any response within a specified time, it will record this
error. If the number of errors exceeds the threshold, DTE will regard the physical
channel and all virtual circuits unavailable. N392 and N393 together define "error
threshold". In other words, if the number of errors reaches N392 among the N393
Status Enquiry messages sent by DTE, DTE will consider that the number of errors
has reached the threshold and the physical channel and all virtual circuits are
unavailable.
Meanings of parameters related to DCE operating mode:
N392 and N393: These two parameters have similar meanings to those related
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to DTE operating mode. However, DCE requires that the fixed time interval for
DTE sending a status-enquiry message should be determined by T392, while
DTE requires that this interval should be determined by T391. If DCE does not
receive the status-enquiry message from DTE within a period determined by
T392, an error recorder is created.
T392: Time variable, which defines the maximum time that DCE waits for a
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status-enquiry message. The time value shall be greater than the value of T391.
Frame relay address mapping associates the protocol address of a remote device
with its frame relay address (local DLCI). By consulting the frame relay address map
by protocol address, the upper layer protocol can locate a remote device.
Frame relay is used to bear IP protocol. When sending an IP packet, the frame
relay-enabled router can obtain its next hop address after consulting the routing
table, which is inadequate for sending the packet to the correct destination across
a frame relay network. To identify the DLCI corresponding to the next hop address,
the router must consult a frame relay address map retaining the associations
between remote IP addresses and next hop DLCIs.
A frame relay address map can be manually configured or maintained by Inverse
Address Resolution Protocol (InARP).
The following figure presents how LANs are interconnected across a frame relay
network.
Figure 41 Interconnect LANs through a frame relay network
Router A
DLCI=50
DLCI=60
DLCI=70
FR
DLCI=80

Frame Relay Terminologies

Router B
Router C
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