Over the past few years, new promising protocols have emerged at the forefront of Metro networking. One among them is the Resilient Packet Ring (RPR). Today, as the standard slowly settle, it is finally reaching the stage beyond speculation, and into network deployment. Pundits and vendors have pinned exceptional hopes on this technology, particularly for effecting a long-awaited transformation of Metro Area Networking.
The Metro remains the last geographical section of the network still largely dependent on late 1980s and early 1990s technology (low to mid-capacity SONET rings), and is clearly in need of data-focused improvements. RPR technology, on their own, adds features to Metro Area Networks that are currently lacking.
A protocol is a set of rules that governs the communications between computers on a network. These rules include guidelines that regulate the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer etc.
commonly used protocols are:
The most common protocols in use today include:
Â¢ Token Ring
Â¢ ATM etc
METROPOLITAN AREA NETWORKS
Metropolitan Area Network (MAN) is a computer network usually spanning a campus or a city, which typically connect a few local area networks using high speed backbone technologies. There are three important features, which discriminate MANs from LANs or WANs:
1. A MAN typically covers an area of between 5 and 50 km range (between LANs and WANs)
2. The MAN, its communications links and equipment are generally owned by either a consortium of users or by a network service provider.
3. A MAN is frequently used to provide a shared connection to other networks using a link to a WAN and to share regional resources.
An important trend in networking is the migration of packet-based technologies from Local Area Networks to Metropolitan Area Networks (MANs). The MAN protocols are mostly at the data link level. Some legacy technologies presently used for for Metropolitan Area Networks (MANs) include :
Â¢ Asynchronous Transfer Mode (ATM)
Â¢ Synchronous Optical NETwork (SONET)
Â¢ Fiber Distributed Data Interface (FDDI)
Â¢ Gigabit Ethernet MANs & 10 Gigabit Ethernet
Asynchronous Transfer Mode (ATM)
The ATM composes a protocol suite, which establishes a mechanism to carry all traffic on a stream of fixed packets called cells. A fixed-size packet can ensure that the switching and multiplexing function could be carried out quickly and easily. ATM is a connection-oriented technology. ATM offers multiservice focus - remedy for carrying data, voice and video.
2.2 Synchronous Optical NETwork (SONET)
SONET is a synchronous system and is controlled by a master clock. The sender and the receiver are connected to the common clock.
2.3 Fiber Distributed Data Interface (FDDI)
FDDI is a set of ANSI protocols for sending digital data over fiber optic cable. FDDI networks are token passing and dual-ring networks, and support data rates of up to 100 Mbps. FDDI uses dual-ring architecture with traffic on each ring flowing in opposite directions (called counter-rotating). FDDI specifies the physical and media-access portions of the OSI reference model.
2.4 Distributed Queue Dual Bus (DQDB)
DQDB is a Data-link layer communication protocol for Metropolitan Area Networks (MANs). DQDB is designed for data as well as voice and video transmission based on cell switching technology (similar to ATM). DQDB permits multiple systems to interconnect using two unidirectional logical buses.
2.5 Switched Multimegabit Data Service (SMDS)
SMDS is a broadband networking technology developed based on the DQDB MAN technology. SMDS can use fiber- or copper-based media; SMDS operates by accepting high-speed customer data in increments of up to 9,188 octets, and divides it into 53-octet cells for transmission through the service providerâ„¢s network, which are reassembled at the receiving end into the customer data.
2.6 10-Gigabit Ethernet
10-Gigabit Ethernet, built on the Ethernet technology, offers data speeds up to 10 billion bits per second. It is used to interconnect LANs, WANs, and MANs. It uses the Ethernet MAC protocol and its frame format and size. It only functions over optical fiber. So it does not need the carrier-sensing multiple-access with Collision Detection (CSMA/CD) protocol as it is used in other Ethernet standards.