Frame Relay A packet-switched technology that made its debut in the early 1990s, Frame Relay is a high-performance Data Link and Physical layer specification. It’s pretty much a successor to X.25, except that much of the technology in X.25 used to compensate for physical errors (noisy lines) has been eliminated. An upside to Frame Relay is that it can be more cost effective than point-to-point links, plus it typically runs at speeds of 64Kbps up to 45Mbps (T3). Another Frame Relay benefit is that it provides features for dynamic bandwidth allocation and congestion control.
ISDN Integrated Services Digital Network (ISDN) is a set of digital services that transmit voice and data over existing phone lines. ISDN offers a cost-effective solution for remote users who need a higher-speed connection than analog dial-up links can give them, and it’s also a good choice to use as a backup link for other types of links like Frame Relay or T1 connections.
LAPB Link Access Procedure, Balanced (LAPB) was created to be a connection-oriented protocol at the Data Link layer for use with X.25, but it can also be used as a simple data link transport. A not-so-good characteristic of LAPB is that it tends to create a tremendous amount of overhead due to its strict time-out and windowing techniques.
LAPD Link Access Procedure, D-Channel (LAPD) is used with ISDN at the Data Link layer (layer 2) as a protocol for the D (signaling) channel. LAPD was derived from the Link Access Procedure, Balanced (LAPB) protocol and is designed primarily to satisfy the signaling requirements of ISDN basic access.
HDLC High-Level Data-Link Control (HDLC) was derived from Synchronous Data Link Control (SDLC), which was created by IBM as a Data Link connection protocol. HDLC works at the Data Link layer and creates very little overhead compared to LAPB. It wasn’t intended to encapsulate multiple Network layer protocols across the same link—the HDLC header doesn’t contain any identification about the type of protocol being carried inside the HDLC encapsulation. Because of this, each vendor that uses HDLC has its own way of identifying the Network layer protocol, meaning each vendor’s HDLC is proprietary with regard to its specific equipment.
PPP Point-to-Point Protocol (PPP) is a pretty famous, industry-standard protocol. Because all multiprotocol versions of HDLC are proprietary, PPP can be used to create point-to-point links between different vendors’ equipment. It uses a Network Control Protocol field in the Data Link header to identify the Network layer protocol and allows authentication and multilink connections to be run over asynchronous and synchronous links.
PPPoE Point-to-Point Protocol over Ethernet encapsulates PPP frames in Ethernet frames and is usually used in conjunction with ADSL services. It gives you a lot of the familiar PPP features like authentication, encryption, and compression, but there’s a downside—it has a lower maximum transmission unit (MTU) than standard Ethernet does, and if your firewall isn’t solidly configured, this little attribute can really give you some grief! Still somewhat popular in the United States, PPPoE on Ethernet’s main feature is that it adds a direct connection to Ethernet interfaces while providing DSL support as well. It’s often used by many hosts on a shared Ethernet interface for opening PPP sessions to various destinations via at least one bridging modem.
Cable In a modern HFC network, typically 500 to 2,000 active data subscribers are connected to a certain cable network segment, all sharing the upstream and downstream bandwidth. ( Hybrid fibre-coaxial , or HFC, is a telecommunications industry term for a network that incorporates both optical fiber and coaxial cable to create a broadband network.) The actual bandwidth for Internet service over a cable TV (CATV) line can be up to about 27Mbps on the download path to the subscriber, with about 2.5Mbps of bandwidth on the upload path. Typically users get an access speed from 256Kbps to 6Mbps. This data rate varies greatly throughout the U.S.
DSL Digital subscriber line is a technology used by traditional telephone companies to deliver advanced services (high-speed data and sometimes video) over twisted-pair copper telephone wires. It typically has lower data carrying capacity than HFC networks, and data speeds can be range limited by line lengths and quality. Digital subscriber line is not a complete endto- end solution but rather a Physical layer transmission technology like dial-up, cable, or wireless. DSL connections are deployed in the last mile of a local telephone network—the local loop. The connection is set up between a pair of modems on either end of a copper wire that is between the customer premises equipment (CPE) and the Digital Subscriber Line Access Multiplexer (DSLAM). A DSLAM is the device located at the provider’s central office (CO) and concentrates connections from multiple DSL subscribers.
MPLS MultiProtocol Label Switching (MPLS) is a data-carrying mechanism that emulates some properties of a circuit-switched network over a packet-switched network. MPLS is a switching mechanism that imposes labels (numbers) to packets and then uses those labels to forward packets. The labels are assigned on the edge of the MPLS of the network, and forwarding inside the MPLS network is done solely based on labels. Labels usually correspond to a path to layer 3 destination addresses (equal to IP destination-based routing). MPLS was designed to support forwarding of protocols other than TCP/IP. Because of this, label switching within the network is performed the same regardless of the layer 3 protocol. In larger networks, the result of MPLS labeling is that only the edge routers perform a routing lookup. All the core routers forward packets based on the labels, which makes forwarding the packets through the service provider network faster. (Most companies are replacing their Frame Relay networks with MPLS today).
ATM Asynchronous Transfer Mode (ATM) was created for time-sensitive traffic, providing simultaneous transmission of voice, video, and data. ATM uses cells that are a fixed 53 bytes long instead of packets. It also can use isochronous clocking (external clocking) to help the data move faster. Typically, if you are running Frame Relay today, you will be running Frame Relay over ATM.
ISDN Integrated Services Digital Network (ISDN) is a set of digital services that transmit voice and data over existing phone lines. ISDN offers a cost-effective solution for remote users who need a higher-speed connection than analog dial-up links can give them, and it’s also a good choice to use as a backup link for other types of links like Frame Relay or T1 connections.
LAPB Link Access Procedure, Balanced (LAPB) was created to be a connection-oriented protocol at the Data Link layer for use with X.25, but it can also be used as a simple data link transport. A not-so-good characteristic of LAPB is that it tends to create a tremendous amount of overhead due to its strict time-out and windowing techniques.
LAPD Link Access Procedure, D-Channel (LAPD) is used with ISDN at the Data Link layer (layer 2) as a protocol for the D (signaling) channel. LAPD was derived from the Link Access Procedure, Balanced (LAPB) protocol and is designed primarily to satisfy the signaling requirements of ISDN basic access.
HDLC High-Level Data-Link Control (HDLC) was derived from Synchronous Data Link Control (SDLC), which was created by IBM as a Data Link connection protocol. HDLC works at the Data Link layer and creates very little overhead compared to LAPB. It wasn’t intended to encapsulate multiple Network layer protocols across the same link—the HDLC header doesn’t contain any identification about the type of protocol being carried inside the HDLC encapsulation. Because of this, each vendor that uses HDLC has its own way of identifying the Network layer protocol, meaning each vendor’s HDLC is proprietary with regard to its specific equipment.
PPP Point-to-Point Protocol (PPP) is a pretty famous, industry-standard protocol. Because all multiprotocol versions of HDLC are proprietary, PPP can be used to create point-to-point links between different vendors’ equipment. It uses a Network Control Protocol field in the Data Link header to identify the Network layer protocol and allows authentication and multilink connections to be run over asynchronous and synchronous links.
PPPoE Point-to-Point Protocol over Ethernet encapsulates PPP frames in Ethernet frames and is usually used in conjunction with ADSL services. It gives you a lot of the familiar PPP features like authentication, encryption, and compression, but there’s a downside—it has a lower maximum transmission unit (MTU) than standard Ethernet does, and if your firewall isn’t solidly configured, this little attribute can really give you some grief! Still somewhat popular in the United States, PPPoE on Ethernet’s main feature is that it adds a direct connection to Ethernet interfaces while providing DSL support as well. It’s often used by many hosts on a shared Ethernet interface for opening PPP sessions to various destinations via at least one bridging modem.
Cable In a modern HFC network, typically 500 to 2,000 active data subscribers are connected to a certain cable network segment, all sharing the upstream and downstream bandwidth. ( Hybrid fibre-coaxial , or HFC, is a telecommunications industry term for a network that incorporates both optical fiber and coaxial cable to create a broadband network.) The actual bandwidth for Internet service over a cable TV (CATV) line can be up to about 27Mbps on the download path to the subscriber, with about 2.5Mbps of bandwidth on the upload path. Typically users get an access speed from 256Kbps to 6Mbps. This data rate varies greatly throughout the U.S.
DSL Digital subscriber line is a technology used by traditional telephone companies to deliver advanced services (high-speed data and sometimes video) over twisted-pair copper telephone wires. It typically has lower data carrying capacity than HFC networks, and data speeds can be range limited by line lengths and quality. Digital subscriber line is not a complete endto- end solution but rather a Physical layer transmission technology like dial-up, cable, or wireless. DSL connections are deployed in the last mile of a local telephone network—the local loop. The connection is set up between a pair of modems on either end of a copper wire that is between the customer premises equipment (CPE) and the Digital Subscriber Line Access Multiplexer (DSLAM). A DSLAM is the device located at the provider’s central office (CO) and concentrates connections from multiple DSL subscribers.
MPLS MultiProtocol Label Switching (MPLS) is a data-carrying mechanism that emulates some properties of a circuit-switched network over a packet-switched network. MPLS is a switching mechanism that imposes labels (numbers) to packets and then uses those labels to forward packets. The labels are assigned on the edge of the MPLS of the network, and forwarding inside the MPLS network is done solely based on labels. Labels usually correspond to a path to layer 3 destination addresses (equal to IP destination-based routing). MPLS was designed to support forwarding of protocols other than TCP/IP. Because of this, label switching within the network is performed the same regardless of the layer 3 protocol. In larger networks, the result of MPLS labeling is that only the edge routers perform a routing lookup. All the core routers forward packets based on the labels, which makes forwarding the packets through the service provider network faster. (Most companies are replacing their Frame Relay networks with MPLS today).
ATM Asynchronous Transfer Mode (ATM) was created for time-sensitive traffic, providing simultaneous transmission of voice, video, and data. ATM uses cells that are a fixed 53 bytes long instead of packets. It also can use isochronous clocking (external clocking) to help the data move faster. Typically, if you are running Frame Relay today, you will be running Frame Relay over ATM.
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