Page 329 - Optical Communications Essentials

Network Management

Network Management 319

ensure that they are configured correctly and operating properly, and that cor-
porate policies regarding network use and security procedures are being fol-
lowed. This is carried out through network management, which is a service that
uses a variety of hardware and software tools, applications, and devices to assist
human network managers in monitoring and maintaining networks. The ISO
has defined five primary conceptual areas of management for networks. These
functional areas are performance, configuration, accounting, fault, and security
management.
The gathering of status information from network devices is done via some
type of network management protocol, such as the Simple Network Management
Protocol (SNMP). This protocol provides the query language for gathering per-
formance information and sending it to a management console. In general, the
SNMP system will discover the topology of the network automatically and will
display it on the management console in the form of a graph. From this display
the human network manager can view the status of a particular network seg-
ment in greater detail.
To deal with standardized management functions in the optical layer, the
ITU-T issued the document G.709, Network Node Interface for the Optical Trans-
port Network (OTN), which describes a three-layer model. This also is referred
to as the Digital Wrapper standard. This standard enables the broad adoption
of technology for managing multiwavelength optical networks. The model
described in G.709 is based on a client/server concept. Client signals such as IP,
Ethernet, or OC-N/STM-M are mapped from an electrical digital format into an
optical format in an optical channel (OCh) layer. The OCh deals with single-
wavelength channels as end-to-end paths or as subnetwork connections between
routing nodes.
ITU-T Recommendation G.692 describes the use of a separate optical service
channel (OSC) in links that contain optical amplifiers. The OSC operates on a
wavelength that is outside of the standard WDM transmission grid being used.
This allows the OSC to control and manage traffic without deploying a separate
Ethernet control connection to each active device in the network.

Further Reading

1. L. Raman, “OSI systems and network management,” IEEE Commun. Mag., vol. 36, pp. 46–53,
March 1998.
2. G. Keiser, Local Area Networks, 2d ed., McGraw-Hill, Burr Ridge, Ill., 2002, Chap. 11.
3. ITU-T Recommendation X.701, Information Technology—Open Systems Interconnection—
Systems Management Overview, August 1997.
4. E. Park, “Error monitoring for optical metropolitan network services,” IEEE Commun. Mag.,
vol. 40, pp. 104–109, February 2002.
5. C. A. Armiento and Y. A. Yudin, “Wavelength managers monitor reconfigurable DWDM net-
works,” WDM Solutions, vol. 4, pp. 45–49, February 2002.
6. R. Ramaswami and K. N. Sivarajan, Optical Networks, 2d ed., Morgan Kaufmann, San Francisco,
2002, Chap. 9.
7. L. Berthelon, “Management of WDM networks,” Proc. 25th European Conf. on Optical
Communications (ECOC), pp. II.94–II.97, September 1999.

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