Menu

atm stands for

WAN Encapsulation Protocol

WAN Encapsulation Protocols

Network layer passes the data to the data link layer for transmission over the physical layer. The Data Link layer creates frames by adding the necessary checks and controls around the Network layer data. The encapsulation on a router serial interface must be configured to guarantee the correct encapsulation method is used. Different WAN technologies use different encapsulation methods. So, the selection of WAN encapsulation protocol depends on the WAN technology and the communicating equipment.

Each WAN encapsulation protocols usually accompany a certain connection type. The important WAN encapsulation protocols are Point-to-Point Protocol (PPP), High-Level Data Link Control (HDLC), Frame Relay, Asynchronous Transfer Mode (ATM), X.25, and Serial Line Internet Protocol (SLIP). HDLC is the most common encapsulation protocol type and most framing protocols are based on it. The following are short descriptions of each type of WAN protocol. In the coming articles, we would discuss the protocols in detail.

WAN Encapsulation Protocols 1

High-Level Data Link Control (HDLC)

HDLC is the default encapsulation protocol type on point-to-point connections, dedicated links, and circuit-switched links when the link uses two Cisco devices. It is a synchronous Data Link layer bit-oriented protocol originally developed from the Synchronous Data Link Protocol (SDLC) and became standardized by ISO as ISO 13239. It provides both connection-oriented and connectionless service. HDLC also provides flow control and error control by using acknowledgements. Cisco uses a proprietary version of the HDLC protocol known as Cisco HDLC (cHDLC).

Point-to-Point Protocol (PPP)

Point-to-Point Protocol (PPP) is another WAN encapsulation protocol of the data link layer that is used to send and receive multiprotocol data between two directly connected computers or network devices. PPP is used between synchronous and asynchronous circuits. It supports several network layer protocols, such as IPv4 and IPv6. It uses HDLC encapsulation protocol, but also has built-in security mechanisms such as PAP and CHAP. PPP is a byte-oriented protocol widely used in broadband network communications. PPP is also known as RFC 1661.

Frame Relay

Frame Relay is a high-performance WAN encapsulation protocol working at the physical layer and data link layers of the OSI reference model. It was originally designed for use across Integrated Services Digital Network (ISDN) interfaces. It is an industry-standard, packet-switched protocol that handles multiple virtual circuits simultaneously. Frame Relay overcomes the time-consuming processes (such as error correction and flow control) employed in previous X.25 protocol. Today, it is used over a variety of network interfaces.

X.25/Link Access Procedure, Balanced (LAPB)

X.25 is a WAN encapsulation protocol suite defined by ITU-T in 1976 for packet-switched communications over WAN. In 1980 it was the most popular WAN encapsulation protocol. It allows several logical channels to use the same physical line and allow data exchange between terminals with different communication speeds.  It defines how connections between a DTE and DCE are maintained for remote terminal access and computer communications in public data networks. X.25 specifies LAPB, a data link layer protocol. It is a predecessor to Frame Relay. It is the oldest packet-switching technique available and was commonly used before the Open System Interconnection (OSI) reference model became standard.

Serial Line Internet Protocol (SLIP)

SLIP uses a standard protocol for point-to-point serial connections using TCP/IP. It is an industry-standard protocol developed in 1984 that supports TCP/IP networking over serial transmission lines. The protocol is used for TCP communication between two machines that are previously configured for communication with each other.  The older dial-up connection to the server is typically the example of the serial line. It provides TCP/IP hosts with dial-up access to the Internet by using SLIP servers located at Internet service providers (ISPs).

Asynchronous Transfer Mode (ATM)

Asynchronous Transfer Mode (ATM) is an international standard for cell relay in which multiple service types are conveyed in fixed-length cells. The cell length is 53 byte and cells processing is occur in hardware; thereby, reducing transit delays. ATM takes advantage of high-speed transmission media such as E3, SONET, and T3.

Ethernet Standards

Different Ethernet Standards

Most widely used technology in networking is Ethernet. As we say in the early lesson that Ethernet work both in the data link layer and the physical layer. Ethernet standards define both the Layer 2 protocols and the Layer 1 technologies. For the Layer 2 protocols, as with all 802 IEEE standards, Ethernet relies on the two separate sublayers of the data link layer to operate, the Logical Link Control (LLC) and the MAC sublayers.

Other LAN types include Token Ring, Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, Fiber Distributed Data Interface (FDDI), Asynchronous Transfer Mode (ATM) and Local Talk. There are different Ethernet standards that support different band of data:-

 

Ethernet standards

Ethernet is the most popular physical layer LAN technology in use now a day. A standard Ethernet network can broadcast data at a rate up to 10 Mbps. Ethernet is popular as it strikes a good balance between speed, cost and ease of installation.

The Institute for Electrical and Electronic Engineers developed an Ethernet standard known as IEEE Standard 802.3. This standard also defines rules for configuring an Ethernet network as well as how the elements in an Ethernet network interact with each other. By adhering to the IEEE standard, network equipment and network protocols can communicate efficiently.

Fast Ethernet

The Fast Ethernet standard has been established for Ethernet networks that need higher transmission speeds. The standard defines for fast Ethernet is IEEE 802.3u. This standard extends the Ethernet speed limit from 10 Mbps to 100 Mbps with little changes to the existing structure. It also provides a better result for video, multimedia, graphics, Internet surfing, and stronger error detection and correction. Fast Ethernet has three types:-

  • 100BASE-TX using Cat-5 and Cat-6 UTP Cable.
  • 100BASE-FX using Fiber Optic Cable.
  • 100BASE-T4 using Cat-3 UTP Cable.

Gigabit Ethernet

Gigabit Ethernet is more for faster than Fast Ethernet networks with applications such as multimedia and VoIP. The Gigabit Ethernet speed is 10 times faster than Fast Ethernet. The Gigabit Ethernet is defined in the IEEE 802.3 standard as a backbone. Ethernet and Fast Ethernet can feed into a Gigabit Ethernet to interconnect high-performance switches, routers, and servers.

10 Gigabit Ethernet

This is the fastest as well as recent of the Ethernet standards. IEEE 802.3ae defines a version of Ethernet with a nominal rate of 10 Gbits/s. The  10 Gigabit Ethernet is 10 times faster than Gigabit Ethernet. The difference with other Ethernet is that it is based entirely on the use of optical fibre connections.

Asynchronous Transfer Mode (ATM)

ATM is the abbreviation of Asynchronous Transfer Mode. It is a cell-based fast-packet communication technique that supports data-transfer rates from sub-T1 speeds to 10 Gbps. It can be integrated into an existing network as needed without any further update the existing network. The technology was basically for the high-speed transmission of all forms of media from basic graphics to full-motion video.

Due to the small size of cells, ATM equipment can transmit large amounts of data over a single connection. It also allows ISPs to assign limited bandwidth to each customer. While this may seem like a downside for the customer, it actually improves the efficiency of the ISP’s Internet connection, causing the overall speed of the connection to be faster for everybody.

Power over Ethernet (PoE)

Power over Ethernet (PoE) is a solution in which an electrical current is run to networking hardware over the Ethernet Category 5 or Category 6 cable. This minimizes the amount of cable needed as well as eliminates the difficulties and cost of installing extra outlets for input AC or DC power to the equipment.