ATIS-0600416.1999(S2015)
Network to Customer Installation Interfaces –
Synchronous Optical NETwork (SONET)
Physical Layer Specification: Common Criteria
A MERICAN N ATIONAL S TANDARD
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ATIS-0600416.1999(S2015), Network to Customer Installation Interfaces – Synchronous Optical NETwork (SONET)
Physical Layer Specification: Common Criteria
Is an American National Standard developed by the Copper/Optical Access, Synchronization, and Transport Committee
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AMERICAN NATIONAL STANDARD
ATIS-0600416.1999 (S2015)
(formerly T1.416-1999)
American National Standard
for Telecommunications –
Network to Customer Installation Interfaces –
Synchronous Optical NETwork (SONET)
Physical Layer Specification: Common Criteria
1 Scope
This standard establishes common criteria for Synchronous Optical NETwork (SONET) interfaces
at standard rates associated with the Network Interface (NI). Covered herein are maintenance
and operation functionality at the SONET Section, Line, and Path layers specifications. Other
necessary criteria for compliance with the proper interfacing of the connecting customer
installation equipment are found in the other document of this series. Compliance with this
standard addresses network and customer installation compatibility and is not to be construed as
a constraint on the internal operations of the network or the customer installation equipment.
Other documents included in the ANSI T1.416 series (at the time that this document was
approved) are listed below.
ANSI T1.416.01-1999, Telecommunications - Network to Customer Installation Interfaces Synchronous Optical NETwork (SONET) Physical Media Dependent Specification: Multi-Mode Fiber
ANSI T1.416.02-1999, Telecommunications - Network to Customer Installation Interfaces Synchronous Optical NETwork (SONET) Physical Media Dependent Specification: Single-Mode Fiber
ANSI T1.416.03-1999, Telecommunications - Network to Customer Installation Interfaces Synchronous Optical NETwork (SONET) Physical Media Dependent Specification: Electrical
The provisions of this standard are intended to be consistent with applicable requirements
concerning safety and environmental conditions.
2 Normative references
The following references contain provisions that, through reference in this text, constitute
provisions of this American National Standard. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to agreements based on this
American National Standard are encouraged to investigate the possibility of applying the most
recent editions of the standards indicated below.
ANSI T1.101-1994, Telecommunications - Synchronization interface standard1)
ANSI T1.102-1993, Telecommunications - Digital hierarchy - Electrical interfaces1)
ANSI T1.102.01-1996, Telecommunications - Digital hierarchy - VT1.5 Electrical Interface1)
ANSI T1.105-1995, Telecommunications - Synchronous Optical Network (SONET) - Basic
Description including Multiplex Structure, Rates, and Formats1)
ANSI T1.105.01-1998, Telecommunications - Synchronous Optical Network (SONET) Automatic Protection Switching1)
______
1)
For electronic copies of some standards, visit ANSI’s Electronic Standards Store (ESS) at www.ansi.org.
For printed versions of all these standards, contact Global Engineering Documents, 15 Inverness Way East,
Englewood, CO 80112-5704, (800) 854-7179.
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1
ATIS-0600416.1999 (S2015)
ANSI T1.105.02-1995,Telecommunications - Synchronous Optical Network (SONET) - Payload
Mappings1)
ANSI T1.105.03-1994, Telecommunications - Synchronous Optical Network (SONET) - Jitter at
Network Interfaces1)
ANSI T1.105.07-1996, Telecommunications - Synchronous Optical Network (SONET) - SubSTS-1 Interface Rates and Formats Specification1)
ANSI T1.105.07a-1997, Telecommunications - Synchronous Optical Network (SONET) - SubSTS-1 Interface Rates and Formats Specification (Inclusion of N x VT Group Interfaces)1)
ANSI T1.231-1997, Telecommunications - Digital Hierarchy - Layer 1 In-Service Digital
Transmission Performance Monitoring1)
3 Definitions, abbreviations, and acronyms
3.1
Definitions
3.1.1
Anomaly: A discrepancy between the actual and desired characteristics of an item.
3.1.2
Bit period: The amount of time required to transmit a logical one or a logical zero.
3.1.3 Customer installation (CI): The arrangement of equipment and wiring on the customer’s
premises that is the responsibility of the customer.
3.1.4
Defect: A limited interruption in the ability of an item to perform a required function.
3.1.5
Functional group: A set of capabilities.
3.1.6 Line overhead: The overhead added to the VT1.5 of VT Group SPE for transport
purposes. The Line overhead consists of a combined Section and Line overhead. There is no
SDH equivalent term at these rates.
3.1.7 Network interface (NI): The specific interface at the point of demarcation between the
Customer Installation and the network.
3.1.8 Scrambler: A randomizing mechanism that replaces the real data bit stream with one (at
the same bit rate) that can be conceived as the process of exclusive ORing the data stream with
delayed copies of itself (for self-synchronous scramblers) or exclusive ORing the data stream
with a bit stream created by the exclusive ORing of an initial pattern with delayed copies of itself
(for frame synchronous scramblers). The process is often represented by generation
polynomials. The intent is to eliminate long strings of ones and zeros to improve the effectiveness
of the clock synchronization. The received signal is descrambled by the inverse process.
3.1.9 VT1.5 interface line terminating element (VT1.5 LTE): Network elements that originate
and terminate VT1.5 interface signals. VT1.5 LTEs can originate or terminate the Line overhead,
of the VT1.5 interface signal.
3.1.10 VT1.5 transport format: The VT1.5 transport format has a 2.048 Mbit/s format. This
format has 32 bytes per 125 µsec frame, allocating 26 bytes for a single VT1.5 synchronous
payload envelope, 1 byte for a VT1.5 pointer, and 5 bytes per frame for Line overhead. This
format multiplexes the 1.728 Mbit/s bandwidth of a single VT1.5 payload and pointer, as well as
320 kbits/s of Line overhead into a 2.048 Mbit/s transport format.
3.1.11 VT1.5 interface: A SONET VT1.5 transmission interface which transports one VT1.5
synchronous payload envelope and pointer (27 bytes per frame) along with a Line overhead (5
bytes per frame). VT1.5 interfaces may be defined for several electrical and optical physical
transport technologies.
2
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ATIS-0600416.1999 (S2015)
3.2
Abbreviations and acronyms
The following acronyms are used throughout this document.
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ADM
AIS
AIS-L
AIS-P
APD
APS
BER
BIP
B-ISDN
CI
CPE
CV
DB
DBm
DCC
DCD
DDJ
EIA
ES-P
ES-PFE
FC1
FC2
FEBE
FEBE-L
FEBE-P
Hz
ISDN
ITU-T
KHz
Km
LED
LOF
LOH
LOP-P
LOS
LTE
Mbit/s
MHz
NCTE
NDF
NE
NI
Ns
NT
OC-N
PMD
POH
PPM
PRS
Ps
PTE
RDI
Add-drop multiplex
Alarm indication signal
Alarm indication signal - line
Alarm indication signal - path
Avalanche photo-diode
Automatic protection switching
Bit error ratio
Bit interleaved parity
Broadband ISDN
Customer installation
Customer premises equipment
Coding violation
Power level in Decibels
Decibels with respect to 1mW
Data communications channel
Duty cycle distortion
Data dependent jitter
Electronics Industry Association
Errored second - path
Errored second - path far end
Fault condition type 1
Fault condition type 2
Far end block error
Far end block error - line
Far end block error - path
Hertz
Integrated services digital network
International Telecommunication Union - Telecom sector
Kilohertz
Kilometer
Light emitting diode
Loss of frame
Line overhead
Loss of pointer - path
Loss of signal
Line terminating equipment
Megabits per second (106 bits/s)
Megahertz
Network channel terminating equipment
New data flag
Network element
Network interface
Nanosecond
Network termination
Optical carrier level-N
Physical medium dependent
Path overhead
Parts per million
Primary reference source
Picosecond
Path terminating equipment
Remote defect indication
3
ATIS-0600416.1999 (S2015)
RDI-L
RDI-LV
RDI-P
REI
RFI
SDH
SEF
SES
SOH
SONET
SPE
STE
STS
UAS-P
UI
UNI
VT
Remote defect indication - line
VT line remote defect indicator for VT1.5 interface
Remote defect indication - path
Remote error indication
Remote failure indication
Synchronous digital hierarchy
Severely errored frame
Severely errored second
Section overhead
Synchronous optical network
Synchronous payload envelope
Section terminating equipment
Synchronous transport signal
STS path unavailable seconds
Unit interval
User-network interface
Virtual tributary
4 Common criteria
4.1
Order of transmission of bits and bytes
The order of transmission of bits and bytes shall be as specified in ANSI T1.105. For all diagrams of
frame structures shown in this standard, bytes shall be transmitted in the following order for each
frame;
a) The uppermost row is transmitted first, byte by byte, from left to right;
b) The second row is transmitted from left to right;
c) The succeeding rows are transmitted in sequential order, from top to bottom, as depicted in
Figure 1.
A SONET frame structure is shown in Figure 1 for illustration.
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For all representations shown in this standard in binary format, bits are numbered within the byte as
shown in Figure 2 with the order of transmission being from left to right. Bit numbers within a
function composed of consecutive bytes are 1-8 in the first byte, 9-16 in the second byte, and so on;
both byte and bit numbering are from left to right.
4
ATIS-0600416.1999 (S2015)
Order of transmission
Frame N
.
.
.
.
POH
Frame N+1
125 microseconds
SPE boundary
SOH & LOH
250 microseconds
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Figure 1 - Order of byte transmission
Bit positions
1
2
3
4
5
6
7
8
Last bit transmitted
First bit transmitted
Figure 2 - Order of transmission of bits within a byte
4.2
SONET overhead definition and utilization
Detailed definitions for the following SONET overhead are defined in ANSI T1.105. The following
clauses provide an abbreviated listing of the available SONET overhead bytes. Not all of these
bytes will be utilized on any or all customer to network applications. The SONET overhead shall
be active across NI as specified in Table 1. The following definitions apply:
– Required (R): These signals at the interface shall contain valid information as defined in
ANSI T1.105.
5
ATIS-0600416.1999 (S2015)
– Optional (O): Valid information may or may not be present in these signals. Use of these
functions shall be a local matter.
– Application-specific functions (A). These functions may be needed for more than one
type of payload but not necessarily for all payloads. The format and coding for these functions
may not be specified in this standard or in ANSI T1.105. These functions are read, interpreted,
or modified by the appropriate equipment.
4.2.1
−
−
−
−
−
−
−
−
A1: Frame alignment
A2: Frame alignment
B1: Section BIP-8
D1-D3: Section data communication channel
E1:Orderwire
F1:Section user channel
J0: Section trace
Z0: Section growth
4.2.2
−
−
−
−
−
−
−
−
−
−
−
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6
VT path overhead
J2: VT path trace
V5: VT path
Z6 and Z7: VT path growth
4.2.5
−
−
STS path overhead
B3: Path BIP-8
C2: STS path signal label
F2: Path user channel
G1: Path status
H4: Multiframe indicator
J1: STS Path trace
N1: Tandem connection maintenance / path data channel
Z3 and Z4: Growth
4.2.4
−
−
−
Line overhead
B2: Line BIP-8
D4-D12: Line data communication channel
E2: Orderwire
H1 and H2: Pointer value
H3: Pointer action byte
K1 and K2: APS channel
M0: STS-1 line REI
M1: STS-N line REI
S1: Synchronization messaging
Z1: Growth
Z2: Growth
4.2.3
−
−
−
−
−
−
−
−
Section Overhead
VT Line Overhead
M1: Line Quality
S1: Synchronization Message
ATIS-0600416.1999 (S2015)
Table 1 - SONET overheads at NIs
Overhead byte
Section overhead
A1 framing
A2 framing
B1 section BIP-8
D1-D3 section data
communication
channel (Data
Com)
E1 orderwire
F1 section user
channel
Function
Usage
Coding
Frame alignment
Frame alignment
Section error monitoring
Section data communications channel
R
R
R
O
11110110
00101000
BIP-8
Orderwire
Section User Channel
O
O
J0 section trace
Section trace
O
Z0 section growth
Section growth
O
Line overhead
B2 line BIP-8
Line error monitoring
R
Line data communications channel
O
Orderwire
Pointer
O
R
Pointer action
R
D4-D12 line data
communication
channel (Data
Com)
E2 orderwire
H1-H2 pointer
H3 pointer action
byte
K1,K2 APS
Automatic protection switch
channel
M0 STS-1 line REI STS-1 line REI
M1 STS-N line REI STS-N line REI
A
R
R
The F1 byte is defined only for
STS-1 number 1 of an STS-N
signal.
Defined only for STS-1 number
one in an STS-N signal. When the
Section Trace function is not
supported or if no value has been
programmed, then 01 Hex shall be
transmitted.
One byte is defined in each STS-1
for future growth except for STS-1
number 1 (which is defined as J0).
BIP-8 for STS-1 or each STS-1 of
STS-N
BIP-8 for STS-Nc
(e.g., BIP-24 for STS-3c)
These bytes shall be provided in
all STS-1 signals within an STS-N
signal.
Concatenation is handled as
defined in ANSI T1.105.
These bytes shall be provided in
all STS-1 signals within an STS-N
signal.
If APS is used it shall operate as
defined in ANSI T1.105.01
STS-1 line only
In a SONET signal at rates at or
above STS-3, one byte, the M1
byte, is allocated for a line REI
function. The M1 byte is located
in the third STS-1 in order of
appearance in the byte interleaved
STS-N frame.
7
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ATIS-0600416.1999 (S2015)
Table 1 (continued)
Overhead byte
Function
S1 synchronization Synchronization messaging
messaging
Z1 growth
Line growth
O
Z2 growth
Line growth
O
Path error monitoring
STS path signal label
R
R
BIP-8
Use as defined in ANSI T1.105
Path user channel
A
Required for use by PTE
Path status
R
Multiframe indicator
A
STS path trace
R
One byte is allocated to convey
back to an originating STS PTE
the path terminating status and
performance.
Only required for VT-structured
payloads
The content of the message is not
constrained by this standard,
since it is assumed to be user
programmable at both the transmit
and receive ends.
STS path overhead
B3 path BIP-8
C2 STS path
signal label
F2 path user
channel
G1 path status
H4 multiframe
indicator
J1 STS path trace
N1 tandem
Tandem connection maintenance /
connection
path data channel
maintenance / path
data channel
Z3-Z4 growth
Growth
VT path overhead
J2 VT path Trace
VT path trace
V5
Path error monitoring, path signal
label, and remote defect monitoring
Z6 VT path growth Growth
Z7 VT Path growth
VT line overhead
M1 line quality
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8
Usage
R
Coding
Defined only for STS-1 number
one in an STS-N signal.
One byte is defined in each STS-1
for future growth except for STS-1
number 1.
In SONET signals at rates above
STS-1 and below STS-192, one
Z2 byte is defined in each STS-1
except the third STS-1 for future
growth interleaved STS-N frame.
A
O
Two bytes are allocated for future
as yet undefined purposes.
O
R
For further study
Use as defined in ANSI T1.105
O
Allocated for future as yet
undefined purposes.
Use as defined in ANSI T1.105
Growth and remote defect monitoring
A
Line Quality
R
One byte is allocated every
superframe (16 kbit/s) for the Line
quality functions. Line quality
functions include the VT1.5 Line
BIP-2, two-bit Line REI, one bit
RDI-LV, one framing check bit,
and two reserved bits.
ATIS-0600416.1999 (S2015)
Table 1 (concluded)
S1
Synchronization
Message
Synchronization Message
R
One byte per superframe
(16 kbit/s) is allocated for a
synchronization message function.
Bits 5–8 of this byte shall be
allocated to carry the same fourbit synchronization message
codes as defined for other SONET
transport interfaces. Bit 2 is a
framing check bit. Bits 1, 3, and 4
of this byte are reserved.
NOTES
R = Required
A = Application specific function
O = Optional
5 Jitter
The following interface output jitter specifications shall apply at the NI. The following specifications
do not apply to the multi-mode optical interfaces. Jitter is treated differently for these interfaces as
detailed in ANSI T1.416.01.
Additional information on receiver jitter and tolerance characteristics is provided in annex C.
Timing jitter at the 51.840 Mbit/s, 155.520 Mbit/s, and 622.080 Mbit/s SONET-based interfaces
shall meet the criteria specified in ANSI T1.105.03
6 Synchronization
In normal synchronous operation, the timing of the SONET frame at all interface points in the
direction of the network to the customer installation shall be traceable to a Primary Reference
Source (PRS) as specified in ANSI T1.101. Also, in normal synchronous operation, the timing of the
SONET frame at all interface points in the direction of the CI to the network shall be traceable to a
PRS.
While in normal operation, the customer installation shall transmit a signal having a bit rate
accuracy equal to that of the received signal by either of the following methods:
−
locking the frequency of its transmitted signal clock to the long-term average of the incoming
signal. (This is often referred to as “loop timing”.)
−
providing equal signal bit rate accuracy from another PRS.2)
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When in a maintenance state (i.e., a synchronization failure condition), the timing of the signals
from the network may lack traceability to a PRS; in that case, the signals at all interface points in
the direction from the network to the CI shall be within ± 20 ppm of the nominal rate specified for
each interface. Also, when in a maintenance state (i.e., a synchronization failure condition), the
timing of the signals from the CI may lack traceability to a PRS; in that case, the signals at all
interface points in the direction from the CI to the network shall be within ±20 ppm of the nominal
rate specified for each interface.
______
2)
Synchronization to an independent source may result in serious degradation where the source is not a
Stratum 1 clock.
9
ATIS-0600416.1999 (S2015)
While the above represents minimum requirements on synchronization for SONET NIs, it does
not address all complexities associated with network synchronization and interfaces. For further
information, the reader is referred to ANSI T1.105.09. Some of the aspects of SONET
synchronization and timing that are dealt with in ANSI T1.105.09 are:
−
the effects of timing anomalies on SONET payload pointers and their respective payloads;
−
synchronization performance expected during the fault transition from fully synchronous
operation to worst-case free-run clocking condition (e.g., what clock holdover characteristics
are specified for SONET network elements).
− stratum compatibility criteria.
7 Maintenance
This clause discusses physical layer maintenance. Physical layer maintenance is accomplished
by monitoring the received signals, as shown in Figure 3.
Figure 3 illustrates the way monitored primitives are used for failure and performance monitoring.
Near-end events and far-end reports, in terms of anomalies, defects, and failures are discussed
below, near-end events and far-end reports shall be used for two purposes:
−
All near-end events and far-end reports shall be processed for performance monitoring
primitives and failures as described in ANSI T1.231.
−
Near-end events shall be used to make up far-end reports for the transmitted signal.
SONET facilities shall terminate at three hierarchical3) levels:
−
section
−
line
−
path
Maintenance capabilities shall be performed by SONET network elements, and are made
possible by maintenance tools built into the overhead fields of the SONET framing structure.
Performance monitoring and failure processing for the physical media, section, line and path shall
be as specified in ANSI T1.231. Near-end events and failures used to make up far-end reports
for the transmitted signal are specified in ANSI T1.105.
______
3)
"Hierarchical" means that the termination of a particular layer requires prior termination of the lower layer(s).
10
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ATIS-0600416.1999 (S2015)
Physical
layer
Receiver
Framing
Near-end defects
Far-end defects
Payload
signal
Near-end anomalies
Far-end anomalies
Far-end
reports
Near-end
events
SONET
facility
Transmitter
Failure and
performance monitoring
processing,
refer to T1.231
Management layer
Figure 3 - Physical layer maintenance functions
7.1
Near-end events and far-end reports
The near-end events and far-end reports summarized in Table 2 shall be used. They are defined
in clauses labeled by the hierarchical level.
Table 2 - Near-end events and far-end reports
Primitives for failure and performance monitoring
Section
Line
Anomaly Defect
BIP-N
SEF/LOF
(S)
Path (facility)
Anomaly
BIP-N (L)
BIP-2 (LV)
Defect
AIS-L
SEF-LV
LOF-LV
Anomaly
BIP-N (P)
REI-L
REI-LV
RDI-L
RDI-LV
REI-P
Defect
LOP-P
AIS-P
TIM-P
UNEQ-P
Far-end
7.2
7.2.1
RDI-P
OR
ERDI-P
Physical media
STS-1 rates and above
A LOS defect occurs upon detection of no transitions on the incoming signal (before
descrambling) for time T, where 2.3 ≤ T ≤ 100 μs.
The LOS defect is terminated after a time period equal to the greater of 125 μs or 2.5 T'
containing no transition-free intervals of length T', where 2.3 ≤ T' ≤ 100 μs.
11
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Near-end
Physical
media
Defect
LOS
ATIS-0600416.1999 (S2015)
7.2.2
VT1.5 rate - Electrical interface
A LOS-LV defect occurs when no transitions on the incoming signal for a time period equal to
175 ± 75 contiguous pulse positions are detected.
A LOS-LV defect is terminated upon detecting at least 20% transitions on the incoming signal
over a time period equal to 175 ± 75 contiguous pulse positions.
7.3
Section
The following primitives apply to the STS-N section level:
−
BIP interleaved parity-8 (section BIP-8) error: A BIP-8 error event is an anomaly that occurs
when the locally computed BIP-8 does not agree with the BIP-8 sent by the signal source.
A BIP code represents the even parity of a given signal for each bit position. Section BIP-8 is
computed over all bits of the previous STS-N(c) frame after scrambling. The computed BIP-8
is placed in the first B1 byte of the next frame before scrambling;
−
Loss-Of-Frame: An LOF defect occurs when a severely errored frame (SEF) persists for a
period of 3 ms. The LOF defect is terminated when no SEF defects are detected for a period
T, where 1 ms ≤ T ≤ 3 ms.
An SEF defect is the occurrence of four or five contiguous errored frame alignment words. A
frame alignment word occupies the A1 and A2 bytes of an STS frame. An SEF defect is
terminated when two contiguous error-free frame words are detected.
7.4
Line
7.4.1
−
STS-1 rate and above
Line BIP-N*8: A BIP-N*8 error event is an anomaly that occurs when the locally computed
BIP-N*8 does not agree with the BIP-N*8 sent by the signal source.
Line BIP-N*8 is computed over all bits of the previous STS-N(c) except for the first three rows
of the SOH, and is placed in the B2 bytes of the current STS-N(c) frame before scrambling;
−
Remote error indication - Line (REI-L): The occurrence of an REI-L > 0 is an anomaly. REI-L
is a count of the difference between the computed line BIP-N*8 and the received B2 bytes.
The count is placed in the M0 byte (STS-1 line signal) or M1 byte (STS-N line signals where N >
1) in the opposite direction of transmission;
−
Alarm indication signal - Line (AIS-L): An AIS-L defect is the occurrence of line AIS in five
contiguous frames. An AIS-L defect terminates when no line AIS is detected in five
contiguous frames.
Line AIS is a STS-N(c) signal containing a valid SOH with bits 6, 7 and 8 of the K2 byte set to
111, and a scrambled all-ones pattern for the remainder of the signal:
−
Remote defect indication - Line (RDI-L): An RDI-L defect is the occurrence of RDI-L signal in
x contiguous frames, where x = 5 or 10. An RDI-L defect terminates when no RDI-L signal is
detected in x contiguous frames.
An RDI-L signal is a "110" in bits 6, 7 and 8 of the K2 byte in STS-1 number 1. It is set by the
far-end source when it detects an AIS-L defect.
--`,,```,,,,````-`-`,,`,,`,
12
ATIS-0600416.1999 (S2015)
7.4.2
−
VT1.5 rate
Line BIP-2: A BIP-2 error event is an anomaly that occurs when the locally computed BIP-2
does not agree with the BIP-2 sent by the signal source.
Line BIP-2 is computed over all bits of the previous frame, and is placed in bits 5 and 6 of the
VT1.5 line quality byte (M1).
−
REI-LV: The occurrence of an REI-LV > 0 is an anomaly. REI-LV is a count of the difference
between the computed line BIP-2 and the received BIP-2 in the line quality byte (M1). The
count is placed in bits 7 and 8 of the VT1.5 line quality byte (M1). in the opposite direction of
transmission.
−
SEF-LV: Under study
−
LOF-LV: Under study
−
RDI-LV: The RDI-LV defect occurs when the presence of the RDI-LV signal in ten contiguous
frames is detected. The RDI-LV defect is terminated when no RDI-LV signal is detected in
ten contiguous.
The RDI-LV signal is the occurrence of a "1" in bit 4 of the line quality byte (M1).
7.5
Path
The following primitives apply to the path level:
−
Path BIP-8: A BIP-8 error event is an anomaly that occurs when the locally computed BIP-8
does not agree with the BIP-8 sent by the signal source.
Path BIP-8 is calculated over all bits of the path overhead and payload before scrambling.
The computed BIP-8 is placed in the B3 byte of the following frame before scrambling;
--`,,```,,,,````-`-`,,`,,`,`,,`---
−
REI-P: The occurrence of an REI-P > 0 is an anomaly. REI-P is a count of the difference
between the Path BIP-8 received in B3 after unscrambling, and the path BIP-8 calculated
over the POH and payload of the previous frame. The count is placed in bits 1-4 of the path
status byte G1 in the opposite direction of transmission;
−
Loss of pointer - Path (LOP-P): LOP-P is a defect that occurs when either a valid pointer is
not detected in eight contiguous frames, or when eight contiguous frames are detected with
the new data flag (NDF) set to "1001" without a valid concatenation indicator (see ANSI
T1.105). A LOP-P is terminated when either a valid pointer with a normal NDF set to "1001",
or a valid concatenation indicator is detected for three contiguous frames or the occurrence
of an AIS-P defect;
−
AIS - Path (AIS-P): An AIS-P defect is the occurrence of the path AIS in three contiguous
frames. An AIS-P detect is terminated when a valid STS pointer is detected with the NDF set to
1001 for a single frame or 0110 for three consecutive frames.
Path AIS is an all ones signal in H1, H1*, H2, H2* and H3, and the entire SPE;
−
Trace identifier mismatch - Path (TIM-P): When activated, the TIM-P defect shall be detected
within 30 seconds when none of the sampled trace identifier messages match the provisioned
expected value. The TIM-P defect shall be terminated within 30 seconds when four-fifths of the
sampled trace identifier messages match the provisioned expected value.
−
Unequipped - Path (UNEQ-P): An UNEQ-P defect occurs when the C2 bytes in five
consecutive frames containing "00000000" are detected. An UNEQ-P defect is terminated
when no C2 bytes in five consecutive frames containing "00000000" are detected.
13
ATIS-0600416.1999 (S2015)
−
RDI - Path (RDI – P: Two types of RDI-P are available, unenhanced (RDI-P) and enhanced
(ERDI-P). Only one type shall be supported by a PTE at a time, and the enhanced type is
preferred. The enhanced type is defined such that it is generally compatible with the RDI-P
−
7.6
−
RDI - Path (RDI-P): An RDI-P defect is the occurrence of the RDI-P signal in 10
contiguous frames. An RDI-P defect terminates when no RDI-P signal is detected in 10
contiguous frames. The setting of RDI-P in response to LOP-P and AIS-P is specified
in ANSI T1.231.
−
ERDI - Path (ERDI-P): An ERDI-P defect is the occurrence of any one of three ERDI-P
signals (codes) in 10 contiguous frames. An ERDI-P defect terminates when no ERDIP signal is detected in 10 contiguous frames. The setting of ERDI-P in response to
LOP-P and AIS-P, TIM-P or UNEQ-P, or PLM-P is specified in ANSI T1.231.
Path label mismatch - Path (PLM-P): This occurs when the C2 bytes in five consecutive
frames contain a payload label different than the labels allowed by the receiver. A PLM-P
defect is terminated when no C2 bytes in five consecutive frames contain a payload label
different than a label allowed by the receiver. PLM-P is not a path level defect, but does
cause the setting of one of the ERDI-P codes. In addition, this code is also used in ATM
services to indicate a loss of cell delineation defect (see ANSI T1.646).
Performance and failure alarm monitoring
Performance and failure alarm monitoring requirements for physical media, section, line, and
path levels shall be as specified in ANSI T1.231.
7.7
Performance monitoring functions
Performance monitoring functions in terms of collection, storage, validity, register size, threshold
and alerting, reporting, accuracy, and resolution shall be the same as for SONET path; that is,
errored second - path (i.e., ES-P and ES-PFE).
--`,,```,,,,````-`-`,,`,,`,`,,`---
14
ATIS-0600416.1999 (S2015)
Annex A
(normative)
SONET VT1.5 Line Interface Common Criteria
This annex describes the rates, formats, and transport overhead for interfaces referred to as
SONET with a rate less than STS-1. Specifically, the additional transport overhead is defined
that allows the transport of virtual tributary (VT) payloads at the VT1.5 level across an interface.
A.1 General
The primary application of the sub STS-1 interface in this standard is for customer premises
interfaces as illustrated in Figures A.1 and A.2. The sub-STS-1 interface could serve for
transporting VTs directly to a Customer Premises Equipment (CPE). Hence, the network
provider could monitor the end-to-end performance of the VT Path all the way to the customer. In
addition, the performance of the sub-STS-1 line can also be monitored.
Other applications of the VT1.5 electrical interface are the transport of VT1.5 SPE's over the
existing DS1 infrastructure. This includes intra-office, inter-office and access applications.
A.2 VT1.5 interface rate
The fundamental VT1.5 interface information rate is 2.048 Mbit/s. This bandwidth is allocated to
32 eight-bit bytes every 125-µsec frame. This bandwidth is further allocated to the VT1.5
synchronous payload envelope and pointer (27 bytes per frame) along with a Line overhead (5
bytes per frame). The assignment of the VT1.5 pointer, VT1.5 payload and VT1.5 interface Line
overhead to this bandwidth is shown in Figure A.3.
The exact line rate used by a VT1.5 line may be different than the 2.048-Mbit/s binary VT1.5
format rate if multilevel line coding schemes are used or if additional bandwidth is used for
transport technology specific purposes (such as framing or additional transport technology
specific overhead).
Specifics of the electrical VT1.5 line coding technique can be found in ANSI T1.102.01. In this
line code, the 32 bytes of the VT1.5 are carried within one DS1 frame using a ternary line code.
The first bit of the first byte of the VT1.5 frame (A1) shall immediately follow the DS1 frame bit.
The VT1.5 format maintains the VT1.5 pointer function. Therefore, the line rate of any physical
optical or electrical transport technology can be referenced to the local NE clock. The local NE
clock is the same line frequency source used by each STS-N and OC-N interface. This results in
the desirable characteristic that an optical or electrical VT1.5 line can be used to transport
network timing.
A.3 Synchronization
Synchronization plays an essential role in the performance of SONET signals. ANSI T1.105.09 is
the minimum SONET clock synchronization standard for SONET interfaces. The synchronization
requirements in ANSI T1.105.09 are applicable for SONET sub-STS interfaces.
--`,,```,,,,````-`-`,,`,,`,`,,`---
A.4 Transport formats
The transport format for the VT1.5 interface is defined at this time.
A.4.1 Frame structure for the VT1.5 interface
As shown in Figure A.3, the VT1.5 transport format superframe consists of four 125 µsec frames.
One complete VT1.5 superframe, as defined in ANSI T1.105, is contained within the VT1.5
transport format superframe. Both the VT1.5 transport format and the STS-1 signal allocate the
same bandwidth for the VT1.5 SPE and VT1.5 pointer bytes. The requirements, characteristics,
15
ATIS-0600416.1999 (S2015)
and behavior of the VT1.5 SPE and VT1.5 pointers are the same for both the VT1.5 transport
format and the STS-1 signal.
A.4.2 VT1.5 transport format Line overhead
The VT1.5 transport format Line overhead contains five bytes of overhead in each 125 µsec
frame. All VT1.5 Line repeaters are thus physical layer only repeaters and not independent
SONET NEs.
A.4.3 VT1.5 transport format pointer
The VT1.5 pointer for the VT1.5 SONET interfaces is the same as the existing VT1.5 pointer for
STS-N or OC-N interfaces. The VT1.5 format pointer uses the same bandwidth and is defined by
the same requirements as VT1.5 pointers for STS-1 interfaces.
A.4.4 VT1.5 transport format synchronous payload envelope
The VT1.5 synchronous payload envelope is the same 26 bytes and is defined by the same
requirements as existing VT1.5 SPEs for STS-1 SONET formats.
A.4.5 VT1.5 transport format framing pattern
The VT1.5 transport format includes the same framing structure and framing pattern as the 2.048
Mbit/s signal in ITU-T G.704. Bit 1 of the framing bytes (A1 and A2) is used for the multiframe
indicator. Bit 1 of A1 is set to a one while bit 1 of A2 is set to zero. The remaining bits of A1 and
A2 form the main framing pattern and are set to 0011011. Bit 2 of the Line Quality byte and bit 2
of the Synchronization Message byte are set to one as a check bit. The framing pattern is shown
in Figure A.4.
NOTE - As described in ANSI T1.102.01, the electrical interface uses a framing structure at the ternary
line code level, and thus does not require the use of this VT1.5 format framing pattern. The VT1.5
format framing pattern specified here exists in anticipation of future, alternative physical layer
specifications such as optical.
A.5 Line overhead functions
A.5.1 Interface layers
A.5.1.1 Physical layer
Electrical interfaces are specified in ANSI T1.102.01. Physical layer management for the VT1.5
line interface shall be accomplished via DS1 ESF fault and performance measurements.
A.5.1.2 Line layer
The Line overhead deals with the reliable transport of the VT1.5 frame and overhead across the
physical medium.
NOTE - Since sub STS-1 interfaces are not intended for use with Line repeaters, there is no need to
distinguish between the Section and Line overhead functions, as is done in ANSI T1.105.
16
--`,,```,,,,````-`-`,,`,,`,`,,`---
ATIS-0600416.1999 (S2015)
A.5.1.3 Path layer
The VT Path layer for the VT1.5 interface is specified in ANSI T1.105.
A.5.2 VT1.5 Line overhead
The VT1.5 Line overhead functions are generated and terminated by VT1.5 Line Terminating
Elements. If Physical layer repeaters are used, they will not generate or terminate VT1.5 Line
overhead.
A.5.2.1 Line Quality (M1)
One byte is allocated every superframe (16 kbit/s) for the Line quality functions. Line quality
functions include the VT1.5 Line BIP-2, two-bit Line REI, one bit RDI-LV, one framing check bit,
and two reserved bits. Figure A.5 shows the structure of the Line Quality byte.
Bits 5 and 6 of the Line Quality byte shall be allocated to the transport format line error monitoring
function. This function shall be a BIP-2 code using even parity. The Line BIP-2 shall be
calculated over all bits of the VT1.5 transport format superframe. The first bit (bit 5) shall be set
such that the parity of all odd-numbered bits (1, 3, 5, and 7) in all bytes in the previous VT1.5
transport format superframe are even. The second bit (bit 6) shall be set such that the parity of
all even-numbered bits (2, 4, 6, and 8) in all bytes in the previous VT1.5 transport format
superframe is even.
Bits 7 and 8 of the Line Quality byte shall be allocated to the transport format REI function. There
are three legal values for the VT1.5 Line REI, 0, 1 and 2 errors. The value of three shall be
interpreted as 0 errors.
Bit 4 of the Line Quality byte shall be allocated to the transport format RDI-LV function. A logical
1 value in this bit indicates a failure of the VT1.5 line receive function.
Bits 1 and 3 are currently reserved.
The support of this byte is required for all applications.
One byte per superframe (16 kbit/s) is allocated for a synchronization message function. Bits 5–
8 of this byte shall be allocated to carry the same four-bit synchronization message codes as
defined for other SONET transport interfaces. Bit 2 is a framing check bit. Bits 1, 3, and 4 of this
byte are reserved. Figure A.6 shows the bit allocations for the Synchronization Message byte,
and Table A.1 defines the messages.
All unused, unassigned and reserved bits and bytes shall be set to binary 0.
Additional overhead functions are under study.
A.6 VT1.5 Maintenance Signals
The general maintenance philosophy used for VT1.5 interfaces is illustrated in Figure A.7. In
Figure A.7, two VT1.5 PTEs are interconnected at the VT1.5 level.
Upon detection of a failure in the incoming signal (e.g., LOS or LOF), the receiving module sends
RDI-LV upstream to indicate this condition to the transmitting module (see A.5.2.1). VT Path AIS
(all-ones code) is sent to the far-end VT PTE(s).
ANSI T1.231 defines defects, anomalies and failure states.
A.6.1 VT Path layer maintenance signals
VT Path layer maintenance signals are defined in ANSI T1.105.
17
--`,,```,,,,````-`-`,,`,,`,`,,`---
A.5.2.2 Synchronization Message (S1)
ATIS-0600416.1999 (S2015)
A.6.1.1 VT line remote defect indication (RDI-LV)
The purpose of this code is to return an indication to the transmitting VT1.5 LTE that the receiving
VT1.5 LTE has detected an incoming line defect. RDI-LV can be used for performance
monitoring purposes and to aid fault sectionalization.
RDI-LV shall be generated within 100 ms by any VT1.5 LTE upon detection of a LOS or LOF
defect. RDI-LV shall continue for at least 20 VT1.5 transport format superframes. RDI-LV shall
be removed within 100 ms when the VT1.5 LTE detects termination of the defect. A VT1.5 LTE
shall accept a new RDI-LV value when it is received in 10 consecutive VT1.5 transport format
superframes.
RDI-LV shall be generated by setting bit 4 of the M1 byte in the VT transport format superframe
to one, and shall be deactivated by setting bit 4 of the M1 byte to zero.
A.7 APS
If provided, the Line protection switching for VT1.5 signals shall be 1+1 unidirectional, and may
operate in either a revertive or nonrevertive mode.
For 1+1 unidirectional switching, each end operates independently of the other end, and byte K1
is not needed to coordinate switch operation.
The need for bi-directional, 1:1, or 1:n switching operation is for further study.
Table A.1 - Synchronization status messages
SONET Synchronization
Quality Level Description
Synchronization unknown
Stratum 1 Traceable
Stratum 2 Traceable
Stratum 3 Traceable
SONET minimum clock (SMC)
Reserved for Network
Synchronization
Don’t Use for Synchronization
18
Quality Level
S1 Bits (b5–b8)
2
1
3
4
5
User Assignable
0000
0001
0111
1010
1100
1110
7
1111
--`,,```,,,,````-`-`,,`,,`,`,,`---
A.7.1 VT1.5 interface APS
ATIS-0600416.1999 (S2015)
VT1.5 signal drops
VT-based
Ring
ADM
CPE
NCTE
NI
DS1, VT1.5,
Fractional T1
Drops
Customer
Premises
Figure A.1 - Example of VT1.5 drop-side interfaces for an access application
VT1.5 signal drops
VT1.5/VTG/OC-1/OC-3
Feeder Line
from CO
Remote
MUX
--`,,```,,,,````-`-`,,`,,`,`,,`---
Customer
Premises
Figure A.2 - Example of sub STS-1 drop-side interfaces for a customer premises application
ROW #
TOH
(Frame #)
1
2
3
4
A1
framing
M1
A2
S1
R
V1
R
V2
R
V3
R
V4
VT1.5 SPE
capacity
500 μs
COLUMN # 1
2-5
6
7-32
R = Reserved for future use
Figure A.3 - VT1.5 interface superframe format
NOTE - Figure A.3 is the same as Figure 4 in ANSI T1.105.07-1996.
19
ATIS-0600416.1999 (S2015)
Frame #
Overhead byte
Byte value
1
A1
10011011
2
M1
x1xxxxxx
3
A2
00011011
4
S1
x1xxxxxx
Figure A.4 - Framing pattern for the VT1.5 interface
Reserved
1
0
Line
RDI-LV
BIP 2
Bit #1
BIP 2
Bit #2
REI
Bit #1
REI
Bit #2
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
bit 8
NOTE: Bit 3 is set to 0 to allow compatibility with E1 framers which regard bit 3 as an alarm bit.
Figure A.5 - VT1.5 interface line quality byte (M1) format
Reserved
1
0
Reserved
Sync
Message
Bit #1
Sync
Message
Bit #2
Sync
Message
Bit #3
Sync
Message
Bit #4
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
bit 8
NOTE: Bit 3 is set to 0 to allow compatibility with E1 framers which regard bit 3 as an alarm bit.
Figure A.6 - VT1.5 interface synchronization message byte (S1) format
VT(S)
VT(S)
VT Path AIS
LOS, LOF
Sub STS-1
Interface
VT1.5 LTE or VTG LTE
RDI-LV
Sub STS-1
Interface
VT(S)
VT1.5 LTE or VTG LTE
--`,,```,,,,````-`-`,,`,,`,`,,`---
Figure A.7 - Maintenance signaling for sub STS-1 interfaces
NOTE - Figures A.4 through A.7 are the same as Figures 5 through 8 in ANSI T1.105.07-1996.
20
ATIS-0600416.1999 (S2015)
Annex B
(informative)
SONET maintenance signals for the NI
The maintenance signals specified in this standard are used to locate and identify a failure
associated with the NI. In the example illustrated in Figure B.1, four possible failure locations are
identified. These locations are (N = Network, CI = Customer Installation):
−
Fault Condition 1 (FC1): Failure between the N-LTE and the CI-PTE in the CI-PTE to N-LTE
transmission direction.
−
Fault Condition 2 (FC2): Failure between the N-LTE and the CI-PTE in the N-LTE to CI-PTE
transmission direction.
−
Network Fault 1: Failure between the N-LTE and the N-PTE in the N-LTE to N-PTE
transmission direction.
−
Network Fault 2: Failure between the N-LTE and the N-PTE in the N-PTE to N-LTE
transmission direction.
In the discussions below, references are made to PTE and LTE. The PTE includes LTE and STE
functionality. Similarly, LTE includes STE functionality. The following actions occur in response
to the four possible failure locations as described below:
−
Fault Condition 1; CI-PTE-To-N-LTE Failure: Here, a failure between the N-LTE and the CIPTE in the CI-PTE-to-N-LTE transmission direction is considered. If the N-LTE detects an
LOS, an LOF, or a Line AIS, it generates STS Path AIS towards the N-PTE and Line RDI
towards the CI-PTE. If the N-LTE detects a LOP, it generates STS Path AIS towards the NPTE. Upon detecting STS Path AIS, the N-PTE generates STS Path RDI towards the CIPTE. The CI-PTE is able to determine that a failure has occurred along the Line (CI-PTE to
N-LTE) and the Path (CI-PTE to N-PTE) of its outgoing transmission direction after detecting
the Line RDI signal and STS Path RDI signals, respectively.
Line RDI is detected when a "110" code is present in bits 6, 7, and 8 of the K2 byte of the
Line layer overhead in five consecutive frames. STS Path RDI is detected when bit 5 of the
G1 byte of the Path layer overhead is set to "1" in ten consecutive frames.
−
Fault Condition 2; N-LTE-To-CI-PTE Failure: Here, a failure that may occur between the NLTE and the CI-PTE in the N-LTE to CI-PTE transmission direction is considered. If the CIPTE detects a LOS, an LOF, or a Line AIS, it generates Line RDI towards the N-LTE and
STS Path RDI towards the N-PTE. If the CI-PTE detects a LOP, it generates STS Path RDI
towards the N-PTE.
The N-LTE is able to determine that a failure has occurred along the Line of its outgoing
transmission direction (N-LTE to CI-PTE) after detecting the Line RDI. The N-PTE is able to
determine that a failure has occurred along the Path of its outgoing transmission direction (NPTE to CI-PTE) after detecting STS Path RDI.
−
Network Fault 1; N-LTE-To-N-PTE Failure: Here, a failure that may occur between the N-LTE
and the N-PTE in the N-LTE to N-PTE transmission direction is considered. If the N-PTE
detects a LOS, an LOF, or a Line AIS, it generates Line RDI towards the N-LTE and STS
Path RDI towards the CI-PTE. If the N-PTE detects a LOP, it generates STS Path RDI
towards the CI-PTE.
The N-LTE is able to determine that a failure has occurred along the Line of its outgoing
transmission direction (N-LTE to N-PTE) after detecting the Line RDI. The CI-PTE is able to
determine that a failure has occurred along the Path of its outgoing transmission direction
(CI-PTE to N-PTE) after detecting STS Path RDI.
21
--`,,```,,,,````-`-`,,`,,`,`,,`---
Signals generated by the CI-PTE towards the customer premises network are not addressed.
ATIS-0600416.1999 (S2015)
−
Network Fault 2; N-PTE-To-N-LTE Failure: Here, a failure between the N-LTE and the N-PTE
in the N-PTE to N-LTE transmission direction is considered. If the N-LTE detects a LOS, an
LOF, or a Line AIS, it generates STS Path AIS towards the CI-PTE and Line RDI towards the
N-PTE. If the N-LTE detects a LOP, it generates STS Path AIS towards the CI-PTE. Upon
detecting STS Path AIS, the CI-PTE generates STS Path RDI towards the N-PTE.
The N-PTE is able to determine that a failure has occurred along the Line (N-PTE to N-LTE)
and the Path (N-PTE to CI-PTE) of its outgoing transmission direction after detecting the Line
RDI signal and the STS Path RDI.
--`,,```,,,,````-`-`,,`,,`,`,,`---
Figure B.1 - Example of SONET equipment associated with the NI
22
ATIS-0600416.1999 (S2015)
Annex C
(informative)
Receiver jitter tolerance and transfer
Receivers that meet the jitter tolerance template described in this annex are reasonably assured
of proper operation when the interface output jitter specifications described in clause 5 are met.
In addition, for loop-timed applications, reasonable jitter transfer characteristics are assumed to
limit the jitter accumulation effect and to aid in the control of SONET pointer movements.
A receiver's jitter tolerance is defined as the peak-to-peak amplitude of sinusoidal jitter applied on
the input signal that causes a 1 dB power penalty. Such a stress test will ensure that no
additional penalty is incurred under operating conditions.
Optical receivers are assumed to tolerate, as a minimum, the input jitter applied according to the
jitter tolerance mask defined in Bellcore's GR-253-CORE.
The same receivers, when utilized for loop timing, are assumed to meet the jitter transfer
specifications also given in GR-253-CORE.
--`,,```,,,,````-`-`,,`,,`,`,,`---
23
ATIS-0600416.1999 (S2015)
Annex D
(informative)
Bibliography
The following documents are for information only and are not essential for completion of the
requirements of this standard.
ANSI T1.105.04-1995, Telecommunications - Synchronous Optical Network (SONET) - Data
Communication Channel Protocols and Architectures1)
ANSI T1.105.05-1994, Telecommunications - Synchronous Optical Network (SONET) - Tandem
Connection Maintenance1)
ANSI T1.105.09-1996, Telecommunications - Synchronous Optical Network (SONET) - Timing
and Synchronization1)
ITU-T Recommendation G.703, Physical /electrical characteristics of hierarchical digital
interfaces, 19911)
ITU-T Recommendation G.704, Synchronous frame structures used at 1544, 6312, 2048, 8488,
and 44736 kbit/s hierarchical levels1)
ITU-T Recommendation G.707, Synchronous digital hierarchy bit rates, 19961)
Bellcore, GR-253-CORE, Synchronous optical network (SONET) transport systems: Common
generic criteria, Issue 24)
T1 Technical Report #33, A Technical Report on Synchronization Network Management Using
Synchronization Status Messages5)
--`,,```,,,,````-`-`,,`,,`,`,,`---
______
4)
To obtain Bellcore documents, contact Bellcore Customer Service, 8 Corporate Place - PYA 3A-184,
Piscataway, NJ 08854-4156. In U.S. & Canada, call 800/521-CORE; all others, 908/699-5800.
5)
Available from the Alliance for Telecommunications Industry Solutions, Suite 500, 1200 G Street, NW,
Washington, DC 20005.
24