420 Chapter A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
10
What effect does changing the default ips and/or ops have on a X.25 transmission?
Altering the input packet size or the output packet size changes the maximum size of the
X.25 packet at the ingress/egress point of the network. The sizes must match in most
situations.
11
What effect does changing the default win and/or wout have on a X.25 transmission?
Altering the window incoming size or the window outgoing size settings changes the
number of packets that can be sent in a single window. The sizes must match on both ends
of the connection.
12
What is a modulo and what are the possible values?
The modulo is a counter that specifies the packet numbering modulus. The default is 8,
and the only other possible value is 128.
Answers to the Chapter 8 Q&A Section
1
Name the Layer 2 of X.25.
The Layer 2 is LAPB.
2
Name the Layer 3 of X.25.
The Layer 3 is X.25.
3
In X.25, what are the two possible roles that a router can play?
The roles are DCE and DTE.
4
What is the function of a PAD in an X.25 network?
The PAD is a device that collects data from asynchronous terminals and outputs that data
encapsulated inside of X.25 packets.
5
The addressing scheme in X.25 is known as what kind of address?
It is known as X.121 addressing.
6
List the parts of the addressing scheme from Question 5.
The parts are DNIC and NTN.
7
How many digits constitute each of the parts of the address from Question 5?
The DNIC has four digits, and the NTN has 811 digits.
8
From where are the addresses used in configuring X.25 obtained?
They are obtained from the PDN provider.