Comp 346/446 Final Exam Study Guide


Here is a summary of the sections (eighth & seventh editions) that may be 
covered on the final:

Chapter 7: (also on midterm)
7.1:    stop-and-wait and sliding windows intro
7.2:    fine-tuning of sliding windows: go-back-N and selective-reject
7.3:    basics of HDLC, a typical link-level sliding-windows protocol.
        HDLC uses sliding windows on a link-level basis

Chapter 8: (also on midterm)
8.1:    FDM (traditional)
8.2:    TDM, revisited. Lots on SONET.

Chapter 9: Spread Spectrum, intro to cellular phones
9.1: 	basic concepts
9.2:	frequency hopping
9.3:	Theoretically this is a prereq to 9.4, but I think you can
	safely omit this.
9.4:	CDMA


Chapter 11:
11.3:   ATM connections & paths
11.4:   ATM cell format
11.5:   ATM over SONET, etc
11.6:   ATM service categories: CBR, VBR-rt, VBR-nrt, ABR, UBR

Chapter 13:
13.1:   Congestion basics
13.2:   Summary of congestion options
13.3:   More congestion appreaches
13.4:   Congestion summary (very short)
13.5:   ATM traffic management, GCRA, Token Buckets and Leaky Buckets
	Note that GCRA is *not* actually in Stallings.
13.6:   ATM-GFR traffic management

Chapter 14:
14.3: 	(2nd-generation) CDMA cellular networks

Chapter 20 (Chapter 19 in 8th edition)
	RSVP (20.2)
	Differentiated Services (20.3)

Also covered: 
GCRA(T,tau): General Cell Rate Algorithm

RSVP	rfc2205, section 1

==============================================  

Here are a few exercises. Problem numbers are 9th/8th/7th editions

Also study the Review Questions at the end of each of the relevant chapters.

Chapter 7

This first group requires a lot of counting-the-packets analysis
1/1/1			
3/3/2
4/4/3
5/5/4 (discussed before in class)

=========

7/7/6			About the role of REJ frames
10/10/9			Basic sliding windows examples

Chapter 8
7/7/7			Meant to be straightforward
9/9/9			Comparative bandwidth problem; less important

Chapter 9
4/4/4			4 & 5 are about FHSS. There's a lot of relatively
5/5/5			obscure detail here

IMPORTANT: Be familiar with the calculations in Table 9.1 (7th, 8th, 9th editions)

Chapter 11
3ab/2ab/2ab	Calculations on fixed v variable-sized ATM cells
4b/3b/3b	ATM cell size

Chapter 13
1/1/1			"Isarithmic" control proposal; less important

4/6/4			ATM v Frame Relay terminology; less important

Chapter 14
2/2/2			Meant to be easy
4/4/4			Relatively straightforward bandwidth calculation
8abcdef/8abcdef/-	IMPORTANT cdma-encoding problem

Here is the problem:

Consider a CDMA system in which users A and B have the Walsh chipping
codes (-1 1 -1 1 -1 1 -1 1) and (-1 -1 1 1 -1 -1 1 1), respectively.
(a) Show the output at the receiver if A transmits a data bit 1 and 
B does not transmit.
(b) Show the output at the receiver if A transmits a data bit 0 and
B does not transmit.
(c) Show the output at the receiver if A transmits a data bit 1 and
B transmits a data bit 1. Assume the received power from both A and B
is the same.
(d) Show the output at the receiver if A transmits a data bit 0 and
B transmits a data bit 1. Assume the received power from both A and B
is the same.
(e) Show the output at the receiver if A transmits a data bit 1 and
B transmits a data bit 0. Assume the received power from both A and B
is the same.
(f) Show the output at the receiver if A transmits a data bit 0 and
B transmits a data bit 0. Assume the received power from both A and B
is the same.

Chapter 20
3/chapter19.#19/-			Straightforward give-examples problem
Here is the problem:
Provide three examples (each) of elastic and inelastic Internet traffic.
Justify each example's inclusion in its respective category.

6/ch19.21/ch19.7		Token-bucket calculation

===================================================================

Recall the GCRA algorithm (this same definition will be given to you
on the exam):
    GRCA(T,tau): Avg time T between packets, tau = variation        
    Suppose current cell is expected at time tat, actually arrives at t
    Case 1: t < tat - tau (too EARLY): NONCONFORMING; do not change tat
    Case 2: t >= tat - tau: CONFORMING; newtat = max(t,tat) + T

Consider the following set of packet arrival times. 

	0  0  3  5  7  9  16  16
	
1. For GCRA(3,2), which packets are compliant?


2. For GCRA(3,1), which packets are compliant?


3. For GCRA(2,10), which packets are compliant?


For each example, also give the values for the theoretical arrival
times (tat).


4. For a GCRA(4,25) flow, 
   (a) how many packets can be sent as a burst at T=0?
   (b) if that burst is sent, at what time can the next packet be sent?


5. For each of the ATM traffic classes CBR, rt-VBR, nrt-VBR, and UBR, 
list the Quality-of-Service (QoS) and Traffic parameters they request.


6. Outline the differences between AAL3/4 and AAL5 in terms of:
(a) data bytes per packet
(b) bits used in ATM header
(c) error detection


7. Suppose an ATM connection meets GCRA(6, 18). 
(a) What is the maximum size of a packet burst?
(b) Assume the available output bandwidth is 1 packet per 4 time units. 
How long does it take to send a packet burst?
(c). What outbound bandwidth is needed if the maximum delay 
is 8 time units?
(d). What outbound bandwidth is needed if the maximum delay 
is 20 time units?


8. Compare and contrast ATM connection admission with RSVP.


9. Give an equivalent definition of GCRA(T,tau) in terms of token buckets.


10. Explain the differences and similarities between admission
control and policing.