AIS AI2524 Configure Additional X.25 Routing Features

AI2524 Router Card User’s Manual
Page 12-38 August 1997
2524UM
Configuration for Router Y
service tcp-keepalives-in
service tcp-keepalives-out
interface ethernet 0
ip address 172.20.1.2 255.255.255.0
!
interface serial 0
x25 ltc 5
x25 pvc 1 tunnel 172.20.1.1 interface serial 0 pvc 2
x25 pvc 2 tunnel 172.20.1.1 interface serial 1 pvc 2
Configure
Additional X.25
Routing Features
To configure other, less common X.25 routing features, perfor m these
tasks:
zConfigure XOT to Use Interface Default Flow Control Values
zSubstitute Addresses in a Local X.25 Rout
zConfigure XOT Alternate Destinations
Configure XOT to Use Interface Default Flow Control
Values
When setting up a connection, the source and des t in ation XOT imple-
mentations need to cooperate to determine the flow control values that
apply to the SVC. The source XOT ensures cooperation by encoding
the X.25 flow control facilities (the window sizes and maximum
packet sizes) in the X.25 Call packet. The far host's XO T implementa-
tion can then correctly negotiate the flow control values at the destina-
tion interface and, if needed, indicate the final values in the X.25 Call
Confirm packet.
The versions of XOT prior to Release 9.1(4.1) software will not, how-
ever, ensure that these flow con tro l values are encoded in the X.25 Call
packet. When XOT receives a call that leaves one or both flow control
values unspecified, it supplies the values. The values supplied are a
window size of 2 packets and maximum packet size of 128 bytes; ac
cording to the standards, any SVC can be negotiated to use these val-
ues. Thus, when XOT receives a call from an older XOT
implementation, it can specify in the Call Confirm packet that thes
flow control values must revert to the lowest common denominator.
What the older XOT implementati ons required was that the so urce and
destination XOT router use the same default flow control values on the
two X.25 interfaces that connect the SVC. Consequently, connections
with mismatched flow control va l ue s w ere created when this assump-