FRM Configuri ng Frame Relay 7-17
Rcv Clock (TT) from DTE
allows the clock to be looped back from the DTE using the TT (Terminal Timing)
signal, which can be helpful on high-speed lines. Generally, if the local interface is
physical DCE and the line speed is above 256 Kbps, this parameter sho uld be set to Y.
(Make sure the remote DTE is configured to provide the terminal timing.)
CSU/DSU Opera ting Mode
determines whether the at tached mo dem connectio n can be n ormal o r limited distance
(LDM), where the distance depends on the wire gauge, number of splice points, and
line speed. For example, 26-gauge wire and a line speed of 64K bps allows a distance
of 15000 feet. Lowering the speed to 56K increases the allowable distance to 18400
feet. If 19-gauge wire is used, the distances can be multiplied by three.
RTS Control
if configured as Constant means that RTS (Request to Send) will always be asserted;
if configured as External, the CSU/DSU will control RTS.
Link Layer Management
determ ines whet h e r, a n d w h at ty pe of, conf i gu r ab l e net w o rk m anagement (e.g., sta tus
enquiries to the port) will be used: none, LMI (Local Management Interface), or ANSI
T1.617 Annex D (an ANSI-standard LMI).
N1 Polling Count
specifies the number of polling cycles between re quests for Full Status r eports, which
includ e statu s of all PVCs on t he phys ical lin k. Eve r y "T1" seconds (see "T1 Link
Integrity Timer" on page 7-17), the logical DTE will send a Status Enquiry to the
networ k , re q ue s t ing status of the netwo rk l i n k. E ach excha n ge of one enq ui ry and one
message (response) is a polling cycle. After every "N1" cycles, an enquiry for a Full
Status report will be sent.
If this port is c onfigured as logical DC E, status enquiries will b e initiated at th e DTE,
and the local node will respond with status messages.
N2 Error Threshold
is the number of link r eliability and/or protocol errors that can occur during the peri od
defined by N3 Monitored Events Count before the logical DCE will be declared
inactive.
N3 Monitored Events Count
is the number of error-free polling cycles after which the DCE will be declared active
if the first poll resulted in an error. If the first poll was error free, the DCE will be
declared active after that poll. (If the N2 Error Threshold is exceeded during the N3
count, the DCE will be declared inactive, and the N3 count will be restarted.)
T1 Link Integrity Timer
determines how often the logical DTE will initiate a Status Enquiry message to the
DCE.
T2 Polling Verification Timer
indicates how long th e logical DCE will wait between Status Enquiry messages from
the DTE before recording an error.