Traffic grooming is the process of grouping many small
telecommunications
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...
flows into larger units, which can be processed as single entities. For example, in a
network
Network, networking and networked may refer to:
Science and technology
* Network theory, the study of graphs as a representation of relations between discrete objects
* Network science, an academic field that studies complex networks
Mathematics
...
using both
time-division multiplexing (TDM) and
wavelength-division multiplexing
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i.e., colors) of laser light. This techn ...
(WDM), two flows which are destined for a common node can be placed on the same wavelength, allowing them to be dropped by a single
optical add-drop multiplexer
An optical add-drop multiplexer (OADM) is a device used in wavelength-division multiplexing (WDM) systems for multiplexing and routing different channels of light into or out of a single-mode fiber (SMF). This is a type of optical node, which ...
. Often the objective of grooming is minimizing the cost of the network. The cost of line terminating equipment (LTE) (also called add/drop multiplexers or ADMs) is the most dominant component in an optical WDM network's cost. Thus grooming typically involves minimizing the usage of ADMs.
This is similar to the use of
virtual channels and
virtual paths in
ATM networks.
Effective grooming requires consideration of the
topology
Topology (from the Greek language, Greek words , and ) is the branch of mathematics concerned with the properties of a Mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformat ...
of the network and the different routes in use. This is especially useful when dealing with
mesh networks.
Grooming Algorithms
The traffic grooming problem has proven to be computationally intractable in the general case. Hence heuristic solutions are typically used.
Electrical-Layer Grooming
Grooms electrical signals at a granularity of
ODUk(k =1, 2(e), 3, 4, or flex).
* Services are transmitted to tributary boards and groomed to line boards through the cross-connect board, encapsulated and mapped to
OTU signals on the line boards, and then transmitted to the WDM side.
* Through electrical-layer grooming, services of different granularity are groomed and encapsulated into one wavelength and output to the WDM side. This enables multiple services to share the bandwidth, greatly improving bandwidth utilization.
Optical-Layer Grooming
Grooms optical signals at a granularity of wavelength (λ) by flexibly selecting transmission paths.
* After receiving
OTU optical signals, the ROADM board creates optical cross-connection paths internally and outputs the signals to specified egresses. Each egress corresponds to a specific path
* Operation personnel can remotely control the transmission paths of optical signals by creating and adjusting cross-connection paths on the NMS
* Optical-layer grooming used together with the ASON technology can implement automatic fault detection and line adjustment to ensure normal transmission of services.
References
TeletrafficOptical-Layer and Electrical-Layer Grooming{{telecomm-stub