EXFO ETS-1000G - Manual (Page 87)

10 Gigabit Ethernet Analyzer 77
13 BERT
BERT (Bit Error Rate Test) is a test that allows determining the main bit
index of link quality, the bit error rate, i.e. the number of bit errors divided
by the total number of transferred bits.
A binary sequence that is known at the far end and the near end is inserted
into an Ethernet frame which is transmitted to the physical media.
At the far end the sequence is compared with the original one and the bit
error rate is calculated. To enable the connection to a TDM network, an
interface converter is used. It converts the packet network traffic
(Ethernet) into the traffic being transmitted across TDM networks.
The test can be implemented on four OSI layers.
On the physical layer data is sent in portions at a certain interframe gap
(IFG). In this case the transmitting fiber optic pair is looped to the receiving
one or the Loopback function is used to conduct the test.
On the data link layer an Ethernet header is added to data, which allows
transmitting test packets across the network that contains the devices
operating on the second layer of the OSI model (for example, a switch).
The methods for connecting the device to the network being tested are
shown in the figures in this chapter.
On the network layer data is inserted into an IP packet, and then it is
inserted into an Ethernet frame. It allows transmitting test packets across
the network which contains the devices operating on the
data link layer
and the network layer (for example, a switch, a router).
The methods for
connecting the device to the network being tested are
shown in the figures.
An Ethernet frame that is generated on the transport layer contains an IP
header and a UDP header, which allows transmitting a test sequence using
transport protocols. The methods for connecting the device to the network
being tested are shown in the images in this chapter.