Alarm Generation & Detection
The
OST monitors and displays SONET or SDH alarms. SONET alarms include
OOF (Out Of Frame), AIS-L (Line Alarm Indication Signal), RDI-L (Line Remote
Defect Indication), REI-L (Line Remote Error Indication) and REI-P (STS
Path Alarm Indication Signal). SDH Alarms include OOF (Out of Frame
Alignment, HP-RDI (Higher-order Path Remote Defect Indication), HP-REI
(Higher-order Path Remote Error Indication), MS-REI (Multiplex Section
Remote Error Indication), MS-AIS (Multiplex Section Alarm Indication Signal).
Anomaly Measurements
The
OST monitors and displays SONET or SDH Anomalies. SONET anomalies
include SONET-ES (, SES and UAS. SDH anomalies include OOF (Out
Of Frame and also called Severely Errored Frames), SDH-BBE (Background
Block Error), ES (Errored Second) and SES (Severely Errored Seconds).
Auto-Establish PPP Session
The
OST automatically negotiates and establishes PPP Sessions. A session is
a series of interactions between two communication end points that occur
during the span of a single connection. Typically, one end point requests
a connection with another specified end point and if that end point replies
agreeing to the connection, the end points take turns exchanging commands
and data ("talking to each other"). The session begins when the
connection is established at both ends and terminates when the connection
is ended. PPP (Point-to-Point Protocol) is a protocol for communication
between two computers using a serial interface. PPP uses the Internet Protocol
(IP). It is sometimes considered a member of the TCP/IP suite of
protocols. Relative to the Open Systems Interconnection (OSI) reference
model, PPP provides layer 2 (data-link layer) service. PPP is a full-duplex
protocol. It uses a variation of High Speed Data Link Control (HDLC)
for packet encapsulation. The OST supports both standard and Cisco
HDLC.
Auto-Negotiate PPP Session
The
OST automatically negotiates and establishes PPP Sessions. A session is
a series of interactions between two communication end points that occur
during the span of a single connection. Typically, one end point requests
a connection with another specified end point and if that end point replies
agreeing to the connection, the end points take turns exchanging commands
and data ("talking to each other"). The session begins when the
connection is established at both ends and terminates when the connection
is ended. The OST supports the negotiation of Maximum-Receive-Unit,
Magic-Number and FCS at the start of a PPP session. PPP (Point-to-Point
Protocol) is a protocol for communication between two computers using a
serial interface. PPP uses the Internet Protocol (IP). It is sometimes
considered a member of the TCP/IP suite of protocols. Relative to the Open
Systems Interconnection (OSI) reference model, PPP provides layer 2 (data-link
layer) service. PPP is a full-duplex protocol. It uses a variation
of High Speed Data Link Control (HDLC) for packet encapsulation. The
OST supports both standard and Cisco HDLC.
Bit Error Rate (BER)
The fraction of received bits in error compared to the total number of
bits received. It is usually expressed as a negative power of 10. For example,
10 e–5 means that one in every 100,000
bits transmitted will be wrong.
Bit Error Rate vs. Optical Signal-to-Noise Ratio
(BER vs. OSNR)
Quantifies
the performance of the optical signal recovery in the presence of
optical noise. The OST monitors Bit Error Rate (BER) while the built-in
Erbium Doped Fiber Amplifier (EDFA) steadily increases the noise
floor to determine the maximum OSNR tolerable for signal recovery
with a BER less than some user-defined limit. Alternatively, the
user may specify a static OSNR level to test under expected system
conditions. Systems with Forward Error Correction (FEC) may also
be subjected to a BER vs OSNR test by an OST since there are two
sets of input and output connectors that are used to connect to external
transmitters and receivers. The OST will optically degrade the DUT’s
transmitted FEC signal. The un-coded FEC signal outputted from a
DUT’s RX to TX is then sent to the OST’s receiver. This
allows systems operating at 12.5 Gb/s, 40 Gb/s, 43 Gb/s or other
rates to undergo a BER vs. OSNR test on an OST.
Degraded Signals
The OST allows a user to test a
device with a variety of calibrated optical signal degradations. The
user can independently, or in combination, degrade the optical signal
by changing the optical power level, extinction ratio, phase and amplitude
jitter, interfering laser power, interfering laser frequency, and Optical
Signal-to-Noise Ratio (OSNR). Layer 2 and layer 3 protocols may be analyzed
while the DUT is subject to a degraded signal to confirm performance
in real-world conditions.
Error Generation
Often
it is useful to stress a Device Under Test with intentionally bad signals
that mimic what happens
in the real world. The OST allows a user to generate bad CRC,
bad IP Checksum or undersize packets.
Extinction Ratio
The ratio of the optical power between the “1” state and
the “0” state of an optical signal. The extinction ratio
of received signals is displayed in the OST’s graphical user interface
and is expressed in dB.
Frame Length
The
Ethernet frame includes preamble, destination address, source address,
type, data field and Frame Check Sequence (FCS). The total byte length
of the Ethernet frame may vary.
Full Line Rate Traffic Generation
The
OST will generate the maximum PoS traffic possible in a 9.9 Gb/s SONET/SDH
system. Users may define every field and choose a range of source
and destination addresses within an appropriate subnet mask.
IP Source & Destination
An
IP Address is also called an Internet Protocol Address. It is a unique,
32-bit number for a specific TCP/IP host on the Internet. IP addresses
are normally printed in dotted decimal form such as 192.100.... There
are two sets of addresses in an Ethernet frame: The MAC Source and Destination
addresses and the IP Source and Destination addresses. The Source
address is the most recent sender's address and the Destination is the
direct recipient's address. MAC Source and Destination addresses
are stripped from the Ethernet frame in a router and have appropriate new
MAC addresses added to send the IP packet towards its IP Destination address
based on the router's routing tables. The IP Source and Destination addresses
are not modified as the packet is sent through the network. The IP
Source and Destination addresses are the original sender's IP addresses
and do not change as an IP Packet is routed through an network.
IPCP Negotiation Parameters
Internet
Protocol Control Protocol sets the IP addresses of the two ports involved
in a PPP session. The OST allows users to set these IP addresses.
LCP Negotiation Parameters
In
the Point-to-Point Protocol (PPP), the Link Control Protocol (LCP) establishes,
configures,
and tests
data-link Internet connections. Before establishing communications over
a point-to-point link, each end of the PPP link must send out LCP packets.
The LCP packet either accepts or rejects the identity of its linked peer,
agrees upon packet size limits, and looks for common misconfiguration
errors. Basically, the LCP packet checks the telephone line connection
to see whether
the connection is good enough to sustain data transmission at the intended
rate. Once the LCP packet accepts the link, traffic can be transported
on the network; if the LCP packet determines the link is not functioning
properly, it terminates the link.
MAC Source & Destination
A
MAC address is the address for a device as it is identified at the Media
Access Control layer in the network architecture. The address is expressed
as a 48-bit hexadecimal number. There are two sets of addresses in
an Ethernet frame; The MAC Source and Destination addresses and the IP
Source and Destination addresses. The Source address is the most
recent sender's address and the Destination is the direct recipient's address.
MAC Source and Destination addresses are stripped from the Ethernet frame
in
a router and have appropriate new MAC addresses added to send the IP packet
towards its IP Destination address based on the router's routing tables.
The IP Source and Destination addresses are not modified as the packet
is sent through the network. The IP Source and Destination addresses
are the original sender's IP addresses and do not change as an IP Packet
is routed through a network.
MPLS Header
The
OST allows multiple MPLS addresses to be set up. Users may fully
define each MPLS header. MPLS (Multiprotocol Label Switching) is
a standards-approved technology for speeding up network traffic flow and
making it easier to manage. MPLS involves setting up a specific path for
a given sequence of packets, identified by a label put in each packet,
thus saving the time needed for a router to look up the address to the
next node to forward the packet to. MPLS is called multiprotocol because
it works with the Internet Protocol (IP), Asynchronous Transport Mode (ATM),
and frame relay network protocols. With reference to the standard model
for a network (the Open Systems Interconnection, or OSI model), MPLS allows
most packets to be forwarded at the layer 2 (switching) level rather than
at the layer 3 (routing) level. In addition to moving traffic faster overall,
MPLS makes it easy to manage a network for quality of service (QoS).
Multiple Statistics
There
are many elements in an Ethernet frame and the OST simultaneously monitors
and displays statistics on more than different 40 categories. Examples
of 10 Gigabit Ethernet LAN statistics the OST keeps include: Frame Sync, FCS Errored
Frames, Dropped Frames, IP Packets, IP Bad Checksum.
Optical Modulation Amplitude (OMA)
The difference in optical power for the nominal “1” and “0” levels
of the optical signal. The OMA of received signals is displayed in the
OST’s graphical user interface and is expressed in dB or mW.
Optical Overload
A measurement of the maximum optical power a receiver can handle before
the Bit Error Rate (BER) reaches
a predetermined unacceptable limit. The OST automatically increases
optical power while monitoring BER up to a user-defined limit.
Optical Power
The average rate of optical energy flow per unit time into or out of
an optical fiber, typically expressed in mW (Milliwatts) or in dBm
(Decibels above 1 mW).
Optical Sensitivity
quantifies
the performance of the optical signal by measuring the Bit Error Rate
(BER) of the received signal
as a function of the input optical power level. The OST automatically
calculates and plots sensitivity. Plots are made on the Circadiant
Straight-Line BER scale to immediately highlight poor sensitivity
performance. The OST measures the sensitivity and determines a pass
or fail depending on whether the sensitivity is better than a specified
value as well as the fit of the data points to a superimposed straight
line and the statistical confidence level that the calculated sensitivity
is correct. The OST will also extrapolate the sensitivity of the
DUT while incorporating the statistical confidence level.
Optical Signal-to-Noise Ration (OSNR)
The measure of the ratio of signal power to noise power in an optical
instrument for a specified optical bandwidth. For a typical optical communication
system for which the OSNR is relevant, the signal consists usually of
nearly monochromatic modulated light superimposed on a background comprised
of (mostly unmodulated) optical power distributed over a broad wavelength
range - a range including the signal wavelength. The OST allows the user
to set the OSNR level of the transmitted signal.
Overhead Editing
The
OST allows a user to overwrite any overhead byte of the first STS-1 except
the calculated bytes of such as A1 or B1.
Path Penalty
A standard measurement of the quality of an optical transmitter. It quantifies
the degradation in transmission
performance between the ideal system with no impairments and a real-world
system with impairments introduced by fiber transmission (e.g. chromatic
dispersion). An external spool of fiber is attached to the OST via
an input loop and an output loop optical connector and is automatically
switched in and out of the measurement path during the optical path
penalty test. The OST automatically measures optical path penalty
in dB.
Percentage of Traffic with Bad FCS
The
OST calculates the ratio of traffic with no Frame Check Sequence (FCS)
errors to the
traffic with errors.
PPP Error Insertion
The
OST will introduce errors at a selectable Bit Error Rate.
PPP Frame Check Sequence Count
Each
PPP packet has a checksum attached to ensure that the data being received
is the data
being sent. If the FCS of an incoming packet is incorrect, the packet
is dropped and the HDLC FCS count is increased. The OST tracks
and displays this information.
RX Error Detection
The
OST monitors and displays B1, B2, and B3 error counts and also calculates
Bit Error Rates.
Selectable Data Field
In
the IP packet there is a Data Field. The OST provides users with
options on how the data field would be filled in, i.e. alternating
1s and 0s.
SONET/SDH Statistics
In
a 10 Gigabit Ethernet WAN (Wide Area Network) application, the Ethernet frame is carried
in a SONET/SDH payload. Thus it is useful to monitor traditional SONET/SDH
Statistics such as Loss Of Frame, B1, B2, and B3 as well as Ethernet
and IP statistics.
Stressed Receiver Conformance
An IEEE 802.3ae specified receiver test. Receivers must operate with a BER
less than 10^-12 at certain optical power levels, depending on the type of
receiver, when tested with specified conditioned input signals that combines
vertical eye closure and jitter. The OST automatically makes Stressed Receiver
Conformance tests. The OST effectively makes a Sensitivity measurement sweep
through the jitter mask at each tested optical power level, with appropriate
filtering, OMA and vertical eye closure to determine the BER at that power
level.
S/x Penalty
is
an Optical Sensitivity measurement used to determine the impact of additional
channels in a fiber on the wavelength being tested and is often used as
a figure of merit for the quality of a receiver. The “S” stands
for Signal and the “x” stands for interfering. The OST uses
an interfering laser approximately 30 nm away from the main wavelength.
The measurement returns two sensitivity plots. The first is with the interfering
laser turned off and the second is with the interfering laser turned on.
The difference in the two plots is the S/x penalty.
TX Error Generation
Often
it is useful to stress a Device Under Test with intentionally bad signals
that mimic what happens in the real world. The OST allows a user
to generate B1, B2 or B3 errors at a specific error rate.
TX Power
The measurement of the intensity of light in dBm or mW from the DUT. The
OST measures the output power of the DUT and determines a pass or fail
depending on whether the power level falls within a specified maximum and
minimum range or is outside of the range.>
User Configurable Parameters
The
OST allows users to define times for the restart timer, max-terminate,
max-configure and max-failure parameters.
10.5 Gb/s, 11.1 Gb/s, 12.5 Gb/s, 40 Gb/s, 43 Gb/s
These
rates refer to 10 Gb/s FibreChannel, FEC encoded 10 Gigabit Ethernet, SuperFEC, SONET
OC-768 (SDH
STM-256), and FEC encoded 40 Gb/s signals respectively. These rates,
and other non-standard rates, may be tested with the OST by inserting
an externally generated optical signal into the reference transmitter
and/or reference receiver ports. The OST is capable of adding degradation
to the inputted signal and performs critical tests such as BER vs.
OSNR on a non-standard signal.
