Bip based-alarm-declaration-and-clearing-in-sonet-networks-employing-automatic-protection-switching

World Academy of Science, Engineering and Technology
International Journal of Electrical, Electronic Science and Engineering Vol:3 No:3, 2009

BIP-Based Alarm Declaration and Clearing in
SONET Networks Employing Automatic
Protection Switching
The SONET STS-1 frame structure is given in Fig.A1 of
the Appendix. For the purposes of this paper, the bytes of
interest are the three BIP bytes B1, B2 and B3 whose scopes
are as follows. The B1 byte is used to detect parity errors per
frame. This is done for the first STS-1 frame in the STS-n
multiplexed frame. It monitors section level bit errors. The B2
byte is used to monitor line-level bit errors, and the B3 byte is
used to monitor path-level bit errors, inclusive of the path
overhead.
A single interleaved parity byte is used to provide error
monitoring across a particular segment along the end-to-end
SONET path. This parity byte performs a parity check on the
previous Synchronous Transport Signal level 1 (STS-1)
frame. During the parity check, the first bit of the BIP octet is
a parity check on the first bit of all octets of the previously
scrambled STS-1 frame. The second bit of the BIP octet is
used exactly the same way, i.e. it is a parity check on the
second bits of each octet of the previous STS-1 frames, and
similarly for the other bits.

Abstract—The paper examines the performance of
bit-interleaved parity (BIP) methods in error rate monitoring, and in
declaration and clearing of alarms in those transport networks that
employ automatic protection switching (APS). The BIP-based error
rate monitoring is attractive for its simplicity and ease of
implementation. The BIP-based results are compared with exact
results and are found to declare the alarms too late, and to clear the
alarms too early. It is concluded that the standards development and
systems implementation should take into account the fact of early
clearing and late declaration of alarms. The window parameters
defining the detection and clearing thresholds should be set so as to
build sufficient hysteresis into the system to ensure that BIP-based
implementations yield acceptable performance results.
Keywords—Automatic protection switching,
parity, excessive bit error rate

bit interleaved

I. INTRODUCTION

T

HIS paper examines the performance of bit-interleaved
parity (BIP) methods in error rate monitoring, especially
for high bit error rates. The term high here is relative. For
example, when the BIP calculation is taken over 801 frames, a
bit error rate (BER) greater than 10-3 is high, in that for values
of BER above this level there is noticeable disparity between
the BIP-based and exact probabilities of bit error in the BIP
word. When the number of frames is 9720 the transition level
is at a BER of 2 10-3, and so on. The reason for this is given
by (3) and (4) and depicted in Fig.4. The analysis presented
here can be applied in SONET systems employing automatic
protection switching (APS). Technical standards exist that
specify requirements (and objectives) for declaring and
clearing alarms. Details of SONET frame structure and
automatic protection switching can be found in
telecommunication standards[1-4] and other texts [5-8].
The protection mechanism can be of two types [6], the 1:1
and 1:n protection mechanisms. Fig.1 (a) depicts
the 1:1 protection architecture where a protection interface is
paired with each working interface. Fig.1 (b) depicts the other
the 1: n protection architecture, consisting of a single
protection facility for several working interfaces. In either
case, when a working interface fails, traffic is automatically
switched over to the protection interface. The failed working
facility is marked with an in both halves of Fig.1.

Head end switch

Tail end switch
Working facility

al
Sign ed
rt
dive

International Science Index 27, 2009 waset.org/publications/6347

Vitalice K. Oduol and Cemal Ardil

protection facility

(a) 1:1 Protection
Head end switch

Tail end switch
Working facility

nal
Sig ed
rt
dive

Working facility
Working facility
protection facility

(a) 1: n Protection
Fig.1 protection switching

When the bit errors exceed certain thresholds, i.e. when
there is an excessive bit error rate condition, the system may
declare an alarm. These conditions when present must be
declared within time limits specified by telecommunication
standards [1,3]. The rest of the paper is organized as follows:
Section II presents a discussion and determination of the bit
error probability in the BIP word. Section III presents the
declaration of the alarm using a sliding window, where first

V. K. Oduol is with the Department of Electrical and Information
Engineering, University of Nairobi, Nairobi, Kenya (+254-02-318262
ext.28327, vkoduol@uonbi.ac.ke)
Cemal Ardil is with the National Academy of Aviation, Baku, Azerbaijan

1


registered as being in error is given by

the window containing the alarm is determined, and then the
alarm is located within the window. Section IV discusses the
clearing of the alarm. In a manner parallel to the declaration of
the alarm, the window containing the alarm clear condition is
first determined, then the alarm clear location is found within
the window. Section IV presents the results and conclusions.
Furthermore, the Appendix provides some information about
the SONET STS-1 frame and some pertinent BIP count
parameters.
II. BIT

ERROR PROBABILITY IN

PExact

2

3

4

A BIP WORD

5

6

7

Exact
BIP Word Bit Error Probability


(4)

1.0

P1

N-1

PN 1
Byte

N

8

Byte 1

Byte

p

1

In addition to the N bytes included in (3) and (4) there is
further potential for bit errors in the BIP byte of the current
frame. This is compared with a calculated version of the BIP
byte. Thus there are N+1 bytes to included in (3) and (4).
These equations are compared in Fig.3 for some typical values
of N listed in Table AI.
For N=801, the BIP-based (3) and the exact (4) values
begin to diverge at a bit error rate of 2 10–4, with the BIPbased value settling at 0.5, and the exact one at 1.0. This trend
is seen for the other values of N. Indeed the point of
separation of the two values gets smaller as N increases, but
for all the cases, the exact traces go to 1.0 whereas the BIPbases trace goes to 0.5. These can be derived from the
expressions already given by letting p tend to 1 in (3) and (4),
respectively.

Fig.2. shows the bytes to be included in the computation of
the bit interleaved parity (BIP) byte. The bit error for the bit
in the second position is registered only if there is a total of an
odd number of errors in the bits considered. If there is only
one byte to consider, the probability that there is a bit error in
the second bit position is p. Suppose N-1 bytes have been
considered so far.
1

1

N

N=87480

N=9720

N=801

0.8

0.6

BIP-Based

0.4
N=87480
0.2
N=9720
N=801

PN

p1 P
N

1

1

0.0
1.0E-06

p PN 1

Fig. 2 Bit interleaved parity probability of bit error for the bit in the
second position of the BIP word

1.0E-05

1.0E-04

1.0E-03

1.0E-02

Actual BER

Fig. 3 Variation of BIP word bit error probability with the number

of bits used in the BIP calculation. Traces for three values of N are
shown

The probability PN that that a bit error is registered for the
second position is obtained by considering two disjoint events.
Either there is an error at the end of the previous stage (N-1)
and no error in byte-N or there is no error at the end of the
previous stage and an error at byte-N. These two give rise to
the equation
(1)
PN p
(1 p) (1 P ) p
N 1

It is also observed that as N increases, the curves in Fig.3 shift
towards the left, the BIP-based traces approaching a limit of
0.5, and the “exact” traces approach unity. Despite the above
disparity of (3) and (4), it is possible to obtain working bit
error rate monitoring methods based on BIP calculations using
a window of an appropriate size and two thresholds one for
declaring alarm, and the other for clearing.
A frame is considered “errored” when it has more than one
bit error in the BIP byte. The probability PFE that a frame is
errored is then
8 8
8 m m
(5)
PFE
1 PN 1
PN 1
m
m 2
A window of size M frames is used and an alarm is declared
if there are N1 or more errored frames in the window.
Conversely, once an alarm is declared the alarm is cleared
when there are N2 or more non-errored frames in a window of
size M frames. Alarm declaration and clearing is cyclic

N 1

which is quickly rearranged as
PN

1 2 p pN 1

(2)

p

with the initial condition that P0 =0.
It is easily verified that the solution to the above equation is

PN

1
1
2

1 2p

N

(3)

Here N is the number of bits included in the calculation. The
exact bit error probability considers that there are N bits and
the probability of bit error is then the complement of the
probability of no bit error in any of the second position bits.
Accordingly the exact probability that a bit in the BIP word is

2



process which consists of four stages as shown in Fig.5. The
analysis uses a sliding window in monitoring the BIP bit
errors. A sliding window has many advantages over a jumping
window. It is therefore widely used in many standard network
protocols, and several authors[9-12] have provided recent
analysis of the performance protocols based on sliding
windows.
For the present objective, a sliding window will have the
advantage over a jumping window in that the spread of the
errors may traverse the boundary of a window, and a jumping
window will fail to catch some of those error patterns that lie
on the window boundaries. A sliding window, on the other
hand will not miss such error patterns.
Returning to Fig.4, it is evident that first there is a hunt for
the window containing the alarm, then the alarm is declared
within the window. For clearing the alarm, there is a hunt for
the window containing the alarm clear, followed by locating
the alarm clear condition within the window. This cyclic
process is repeated for as long as the system runs, being
restarted only when the bit error estimates dictate that the
window parameters M, N1 and N2 should be changed. The
detailed descriptions of the components of Fig.3 are given in
the sections that follow.
III.

The process involves first hunting for the window
containing the alarm, followed by locating the alarm within
the window. The first block after the summing point
represents the fact that the system waits for the occurrence of
an “errored” frame.
The length KD of time in frames up to and including the
errored frame is a geometrically distributed random variable
satisfying the distribution
k 1
k 1
(7)
Prob K D
k
PFE 1 PFE
whose moment generating function PKD(z) is

ALARM DECLARATION

m N
1

m

(8)

1 z 1 PFE

Once the first errored frame is found, the system examines the
subsequent frames keeping two counts, the number of frames
examined, and the accumulated number of errored frames so
far. If the number of frames reaches the window size before
the number of errored frames reaches the threshold N1, the
search begins afresh. This is the event that there are fewer
than N1–1 errored frames in a window of size M–1, where
appropriate allowance has been made for the fact that one
errored frame occurs at the beginning of the target window.
Thus the probability Q that the search begins afresh is then
given by

The unconditional event that a window contains an alarm is
equivalent to the event that there are at least N1 errored frames
in a window of size M. This gives the probability PDeclr of
alarm declaration as
M
M m
(6)
M m
PDeclr

zPFE

PKD ( z )

N
1

2

Q
m 0

M 1
M m 1 m
1 PFE
PFE
m

(9)

If the search results in locating the window with alarm, then
point at which the alarm is declared has to be determined.
There is no need to examine the whole window if the required
number of errored frames has been reached. Thus the length
of time to the declaration of the alarm is another random
variable.

PFE 1 PFE

To locate, declare and clear alarms, the implementation of the
bit error rate monitoring uses a sliding window as depicted in
Fig.4.
Hunt for window with alarm
zPFE

A. Waiting Time to Reach Window Containing Alarm
At this point it is reasonable to obtain an expression for the
waiting time to the window containing the alarm. This is done
via its moment generating function TWD(z). The feedback
diagram of Fig.4 can be used to give
z 1 Q PFE
(10)
T (z)

1-Q

1 z 1 PFE

Q

zM 1

WD

Alarm Declared

Locate
Alarm

It is noted that for z = 1, the denominator of this expression is
zero for Q = 1. The quantity in (10) being a moment
generating function is required to be analytic inside and on
the unit disc { z: |z| 1}. This requirement will be violated
for Q = 1. Indeed, the mean time to the alarm window which
is obtained as

Hunt for clear window
z 1 PFE

1-P

1 zPFE

P

z

Alarm Cleared

z M QPFE

1 z 1 PFE

d
( z)
T
dz WD

M 1

1
z

1

M 1 QPFE

(11)

1 Q PFE

reveals that for values of Q close to 1, the system waiting
time on average will be unacceptably large. Thus, the window
parameters M and N1 of the system must be chosen to ensure
that Q is far enough away from 1. The observations made on
(10) and (11) are a consequence of the sliding window

Locate
Alarm Clear

Fig. 4 Alarm declaration and clearing

3


section is very similar to the preceding one, the difference
being that whereas the hunt for the alarm counts the errored
frames, here it is the non-errored frames that are counted, and
the parameter N1 is now replaced by N2. With reference to
Fig.4, the parameter PFE is replaced by 1–PFE , and Q is
replaced by P, defined similar to (9) as

mechanism; it remains to be seen if the BIP calculations are
sensitive to this fact. This is deferred to the results presented
later.
B. Locating the Alarm Within Window
At this point the window containing the alarm has been found.
An accumulated count is kept within the window the errored
frames, and the alarm is declared as soon as the number of
errored frames reaches the threshold N1; there is no need to
reach the end of the window. This is done in the block
containing the moment generating function TD(z) in Fig.4.
The probability PDeclr (j) of declaring an alarm after j frames
is the event that in the preceding j –1 frames there are N1 – 2
errored frames, followed by an errored frame. The probability
of this event is then
j 1
N1 1
j N1 1
PFE 1 PFE
N1 2


PDeclr ( j )

N

j N 1
1

P
N1 2 FE

1 PFE

dz

WD

z

1

dz

D

N1 1

1 Q PFE

m N

A. Waiting Time to Reach Window To Clear Alarm
Exploiting the similarity with the preceding development, the
waiting time TWC in frames required to reach the window is
defined via its moment generating function TWC(z) as
z 1 P 1 PFE
(18)
T ( z)
WC

PFE

1 zPFE

z M P 1 PFE

The mean time to the clear window is obtained as
d
T
( z)
dz WC

M 1 P 1 PFE

1
z

(19)

1 P 1 PFE

1

As before, it also holds here that for values of P close to 1,
the system waiting time on average will be unacceptably large,
which underscores once more the fact that the window
parameters M and N2 must be chosen to ensure that P is far
enough away from 1.

1

B N1 1, j , PFE

B. Locating the Alarm Clear Within Window
The window containing the alarm clear condition having been
located, the alarm clear is indicated as soon as the number of
non-errored frames reaches the threshold N2; there is no need
to reach the end of the window. The probability PClear (j) of
clearing an alarm after j frames is the event that in the
preceding j –1 frames there are N2–2 non-errored frames,
followed by a non-errored frame. The probability of this event
is then

j N 1
1

ALARM CLEARING

m

(19)

1 zPFE

with the corresponding one for clearing of the alarm, is
evaluated for different system parameters.

The unconditional probability that a window of size M
contains an alarm clear condition is equivalent to the event
that there are at least N2 non-errored frames in a window of
size M. In an analogous manner to (6), this gives the
probability of alarm clearing as
M
M M m
(16)
m
PClear

z 1 PFE

PKC ( z )

where is B(N1-1, j, PFE) is the binomial probability of N1-1
successes in j Bernoulli trials, and PFE is the probability of
success. This quantity along with the corresponding one for
clearing of the alarm can be evaluated for different system
parameters.
IV.

(17)

whose moment generating PKC(z) is

Substituting (10) and (13) in (14) gives the mean alarm
declaration time as
M 1
1 M 1 QPFE
(15)
T1

m
M
PFE m 1 1 PFE

C

(12)

z

z

1

m

and is the probability that there are fewer than N2 - 1
non-errored frames in the window of size M-1. As before the
length KC of time in frames up to and including the
terminating non-errored frame is a geometrically distributed
random variable satisfying the distribution
k
k 1
(18)
Prob K
k
1 PFE PFE 1

The random variables TWD and TD referred to in (10) and (13),
respectively, are statistically independent. The total time T1 to
declare the alarm is the sum of these two.
d
d
(14)
(z)
T
T
T ( z)
1

M

m 0

To obtain the probability of an alarm declaration the
expression in (12) can be summed for j = N1 –1 to M–1, and
incorporating a multiplying factor to cater for the fact that (12)
is a conditional probability. This is a much longer method than
the expression given in (6), which considers that there at least
N1 errored frames in the window for the alarm to be declared.
Given that the window containing the alarm has been
located, the remaining waiting time TD to alarm declaration is
then given via its moment generating TD(z) as
M 1
j 1
N1 1
(13)
j N1 1 j
TD ( z )

2

2

P

PClear ( j )

j 1
j N 1
N 1
PFE 2 1 PFE 2
N2 2

(20)

The probability that an alarm is cleared within the window can
be obtained by summing the above for j = N2 –1 to M–1.
That is
M 1
(21)

1 PFE

PClear

2

The same sliding window above is used in the bit error rate
monitoring to locate the condition to clear the alarm. This

j N

PClear ( j )

2

1

The expressions in (16) and (21) are equivalent since they

4


of the telecommunication standards, show a deviation. For
example when BER = 5.62 10-4 the declaration times are
14.502 ms (BIP) and 6.17 ms (exact). This indicates that the
BIP-based system declares the alarm later than should be case.
This poses a challenge to the standards developers to
ensure that the alarm declaration thresholds are set so that
even though the alarm are set later the results can still be used
to guarantee acceptable network performance .

refer to the same events. The results provided here are
obtained based on (16). In practice the parameters M, N1 and
N2 are chosen to ensure that the declaration and clearing
probabilities meet certain requirements established by
applicable telecommunication standards such as [1] and [3].
Having located the window containing the alarm clear, the
next task is to locate the alarm clear within the window. The
remaining waiting time TC to alarm clearing is then given via
its moment generating TC(z) as
M 1
j 1
N2 1
(22)
j N2 1 j
TC ( z )

j N

2

1

N2

2

PFE

1 PFE

1.000

z

T2

d
( z)
T
dz WC

z

1

d
T ( z)
dz C

Declaration Time [s]

The total time to clear the alarm T2 is the sum of these two
(23)
z

1

Substituting (18) and (22) in (23) gives the mean time in
frames to alarm clearing as


T2

1

M

1 P 1 PFE

1 P 1 PFE

M 1

N2 1

j N

B N 2 1, j , 1 PFE
2

(24)

0.010

0.001
1.0E-04

1.0E-03

1.0E-02

1.0E-01

Actual BER

Fig. 5 Alarm declaration tims for N = 801

Table II and Fig.6 give the alarm clearing times. Evident
from theses results is the fact that the clearing times higher
values of the bit error rate are much lower for the BIP-based
sliding window that those obtained by the exact calculations.
Indeed for BER = 1.78 10-3 the clearing times are
186.424 seconds (BIP) and 7894.36 seconds (exact). This
indicates that the BIP-based system clears the alarm too soon.
Whereas the exact calculation indicates a clearing time of over
2 hours, the BIP-based version clears the alarm in just over 3
minutes.

V. RESULTS AND CONCLUSION
From Fig.4 it has already been observed that the two
expressions (3) and (4) for the bit error probability in the BIP
byte deviate as the prevailing bit error rate increases, giving
the first indication that the BIP-based results may differ from
the actual situation. When the bit error rate is low, the
deviation is small. The onset of deviation depends on, and
decreases with, the number N of frames used in the BIP
calculation. The sliding window parameters N = 801, M = 64,
N1 = 49, and N2 = 13 were used to generate the results
presented here. Table I and Fig.5 give the results for the
declaration times in seconds for sliding window parameters
indicated.

TABLE II
ALARM CLEARING TIMES FOR N = 801
BER

1.00E-04
1.78E-04
3.16E-04
5.62E-04
1.00E-03
1.78E-03
3.16E-03
5.62E-03
1.00E-02

TABLE I
ALARM DECLARATION TIMES FOR N = 801

1.00E-04
1.78E-04
3.16E-04
5.62E-04
1.00E-03
1.78E-03
3.16E-03
5.62E-03
1.00E-02

BIP-Based

1

where B(N1–1, j, 1–PFE) is the binomial probability of N2–1
successes in j trials, and 1–PFE is the probability of success.
This quantity along with the corresponding one for the
declaration of the alarm can be evaluated for different system
parameters and the results compared for both the BIP-based
and exact methods. Rather than clutter the presentation with
too many results, only those corresponding to N=801 are
given here.

BER

Exact
0.100

Declaration Times [s]
BIP-Based
Exact
1.0101E+17
1.2602E+13
7.5248E+13
7.9066E+11
6.6743E+02
7.6287E+00
1.4502E-02
6.1729E-03
6.1415E-03
6.1272E-03
6.1315E-03
6.1250E-03
6.1297E-03
6.1250E-03
6.1296E-03
6.1250E-03
6.1296E-03
6.1250E-03

Clearing Times [s]
BIP-Based
Exact
6.13184E-03
6.12400E-03
1.77828E-03
1.55730E-03
2.47037E-04
2.87339E-04
1.15087E-03
1.52998E-03
2.65636E-01
4.44014E-01
1.86424E+02
7.89436E+03
4.27356E+03
3.34928E+08
6.35641E+03
4.92620E+14
6.40483E+03
2.79511E+25

The scenario presented here is that the BIP-based result
indicates an alarm declaration later and clears the alarm too
soon. The sliding window algorithm to be established to take
into account the fact that there may be delayed declaration and
false clearing of the alarms. Fortunately, the standards
developers have built some hysteresis into the requirements
[1] to guard against false clearing.
The benefits of the analysis are to the standards developers

The declaration times while compliant with the requirements

5


TABLE AI.
BIP COUNT PARAMETERS
BIP Type
Signal
N
B1
STM-0 / STS-1
810
B1
STM-1 / STS-3
2,430
B1
STM-4 / STS-12
9,720
B1
STM-12 / STS-48
29,160
B1
STM-48 / STS-192
87,480
B2
All signals
801
B3
VC-3 / STS-1
783
B3
VC-4 / STS-3c
2,349

who must set the requirements to ensure that when BIP-based
error monitoring is employed there will be disparities with the
exact results. For the implementers of the network elements,
the analysis presented here will be useful in setting the sliding
window system parameters, to ensure that acceptable
performance is achieved.
1.00E+05
1.00E+04
Exact

Clearing Time [s]

1.00E+03

REFERENCES
[1] SONET Transport Systems; Common Generic Criteria, Bellcore
publication GR-253 CORE, Section 5.3
[2] ANSI T1.105: SONET - Basic Description including Multiplex
Structure, Rates and Formats
[3] ANSI T1.105.01: SONET - Automatic Protection Switching
[4] ANSI T1.105.07: SONET - Sub-STS-1 Interface Rates and Formats
Specification
[5] International Engineering Consortium, “SONET Tutorial”, Available
http://www.iec.org/online/tutorials/sonet/topic03.asp
[6] U. Black, S. Waters, Sonet and T1: Architectures for Digital Transport
Networks, 2nd ed, Prentice Hall, 2005
[7] M.N. Ellanti, S.S. Gorshe, L.G. Raman, W.D. Grover, Next Generation
Transport Networks: Data,Mmanagement, and Control Planes,
Springer, 2005
[8] H. G. Perros, Connection-Oriented Networks: SONET/SDH, ATM,
MPLS, and Optical Networks, Wiley 2005
[9] D. Chkliaev, J. Hooman ,E. de Vink, “Formal Verification of an
Improved Sliding Window Protocol” in Proc. 3rd Progress Symposium
on Embedded Systems, 2002, Utrecht, The Nethelands, October 2002,
pages 77-82.
[10] Mark A. Smith and Nils Klarlund. Verification of a Sliding Window
Protocol Using IOA and MONA. FORTE/PSTV 2000, Pisa, Italy,
October 2000, pages 19-34.
[11] Eric Madelaine and Didier Vergamini. Specification and Verification of a
Sliding Window Protocol in LOTOS. FORTE '91, Sydney, Australia,
November 1991, pages 495-510.
[12] Y. Deng, Z. Huang, “Modeling and Performance Analysis of a Sliding
Proc. 4th Progress Symposium on Embedded
Window Protocol”
Systems, pp. 60-65, Utrecht, STW, The Netherlands October 2003

1.00E+02
1.00E+01

BIP-Based

1.00E+00
1.00E-01
1.00E-02

1.00E-04
1.00E-04

1.00E-03

1.00E-02

Actual BER

Fig. 6 Alarm clearing times for N=801

APPENDIX
Fig.A1 shows the SONET STS-1 frame indicating the
overhead bytes and their functions. Table AI shows the values
of the number of frames used in the BIP calculations. The data
in this table can be used together with (3) and (4) to obtain the
probability that a bit in the BIP word is indicated as being in
error.
Synchronous payload envelope (SPE)

3 bytes
Section
Overhead
Line
Overhead

87 bytes

Vitalice K. Oduol received his pre-university education at Alliance High
School in Kenya. In 1981 he was awarded a CIDA scholarship to study
electrical engineering at McGill University, Canada, where he received the
B.Eng. (Hons.) and M.Eng. degrees in 1985 and 1987, respectively, both in
electrical engineering. In June 1992, he received the Ph.D. degree in electrical
engineering at McGill University.
He was a research associate and teaching assistant while a graduate student
at McGill University. He joined MPB Technologies, Inc. in 1989, where he
participated in a variety of projects, including meteor burst communication
systems, satellite on-board processing, low probability of intercept radio,
among others. In 1994 he joined INTELSAT where he initiated research and
development work on the integration of terrestrial wireless and satellite
systems. After working at COMSAT Labs. (1996-1997) on VSAT networks,
and TranSwitch Corp.(1998-2002) on product definition and architecture, he
returned to Kenya, where since 2003 he has been with Department of
Electrical and Information Engineering, University of Nairobi.
Dr. Oduol was a two-time recipient of the Douglas tutorial scholarship at
McGill University. He is currently chairman, Department of Electrical and
Information Engineering, University of Nairobi. His research interests include
performance analysis, modeling and simulation of telecommunication
systems, adaptive error control, feedback communication.

Path Overhead

3 rows

Transport
Overhead

9 rows


1.00E-03

A1 Framing

A2 Framing

B1 BIP-8

E1 Orderwire F1 User

C1 STS-1 ID

J1 Trace
B3 BIP-8

D1 Datacom

D2 Datacom

D3 Datacom

C2 Signal Label

H1 Pointer

H2 Pointer

H3 Pointer Action

G1 Path Status

B2 BIP-8

K1 APS

K2 APS

F1 User

D4 Datacom

D5 Datacom

D6 Datacom

H4 Multiframe

D7 Datacom

D8 Datacom

D9 Datacom

Z3 Growth

D10 Datacom D11 Datacom D12 Datacom

Z4 Growth

A1 - Framing

Z5 Growth

A1 - Framing

E2 Orderwire

Cemal Ardil is with the National Academy of Aviation, Baku, Azerbaijan

Fig. A1 SONET STS-1 Overhead bytes and their functions

6

Bip based-alarm-declaration-and-clearing-in-sonet-networks-employing-automatic-protection-switching

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