Compare Internet connection types Flashcards
IXPs
The Internet is a global network of networks. The core of the Internet consists of high bandwidth fiber optic links connecting Internet exchange points (IXPs). These trunk links and IXPs are mostly created by telecommunications companies and academic institutions.
ISPs
Internet service providers (ISPs) establish high-speed links between their networks, using transit and peering arrangements to carry traffic to and from parts of the Internet they do not physically own.
Customers connect to the Internet via an ISP’s network. The connection to the ISP’s network uses its nearest point of presence (PoP), such as a local telephone exchange
Internet connection type
An Internet connection type is the media, hardware, and protocols used to link the local network at a domestic residence or small office to the ISP’s PoP.
This WAN interface is typically point-to-point. This means that there are only two devices connected to the media (unlike Ethernet). Where Ethernet connections are made using NICs and switches, the connection to a WAN interface is typically made by a type of digital modem.
The roll of router and IP
The modem establishes the physical connection to the WAN interface, but when interconnecting networks, there must also be a means of identifying each network and forwarding data between them. This function is performed by a router that implements the Internet Protocol (IP).
Digital Subscriber Line (DSL)
Digital subscriber line (DSL) uses the higher frequencies available in these copper telephone lines as a communications channel. The use of advanced modulation and echo cancelling techniques enable high bandwidth, full duplex transmissions.
There are various “flavors” of DSL, notably asymmetrical and symmetrical types:
Asymmetrical DSL (ADSL) provides a fast downlink but a slow uplink. There are various iterations of ADSL, with the latest (ADSL2+) offering downlink rates up to about 24 Mbps and uplink rates of 1.25 Mbps or 2.5 Mbps.
Symmetric versions of DSL offer the same uplink and downlink speeds. These are of more use to businesses and for branch office links, where more data is transferred upstream than with normal Internet use.
The customer network is connected to the telephone cabling via a DSL modem. A filter (splitter) must be installed to each phone socket to separate voice and data signals.
RJ11 DSL (left) and RJ45 LAN (right) ports on a DSL modem.
Cable Modems
A cable Internet connection is usually available as part of a cable access TV (CATV) service. A CATV network is often described as hybrid fiber coax (HFC), as it combines a fiber optic core network with copper coaxial cable links to customer premises equipment.
Cable based on the Data Over Cable Service Interface Specification (DOCSIS) supports downlink speeds of up to 38 Mbps (North America) or 50 Mbps (Europe) and uplinks of up to 27 Mbps. DOCSIS version 3 allows the use of multiplexed channels to achieve higher bandwidth.
The cable modem is interfaced to the local router via an RJ45 port and with the access provider’s network by a short segment of coax terminated using threaded F-type connectors.
The RJ45 port connects to the local network router, while the coax port connects to the service provider network.
Fiber to the Curb and VDSL
Very-high-bit-rate Digital Subscriber Line(VDSL) is a type of DSL (Digital Subscriber Line) technology that provides faster data transmission speeds compared to older DSL technologies like ADSL.
A fiber to the curb (FTTC) solution retains some sort of copper wiring to the customer premises while extending the fiber link from the point of presence to a communications cabinet servicing multiple subscribers.
VDSL achieves higher bit rates than other DSL types at the expense of range. It allows for both symmetric and asymmetric modes. Over 300 m (1,000 feet), an asymmetric link supports 52 Mbps downstream and 6 Mbps upstream, while a symmetric link supports 26 Mbps in both directions. VDSL2 specifies a very short range (100 m/300 feet) rate of 100 Mbps (bi-directional).
Fiber to the Premises and Optical Network Terminals
A fiber to the premises (FTTP) Internet connection means that the service provider’s fiber optic cable is run all the way to the customer’s building. This full fiber connection type is implemented as a passive optical network (PON). In a PON, a single fiber cable is run from an optical line terminal (OLT) to a splitter. The splitter directs each subscriber’s traffic over a shorter length of fiber to an optical network terminal (ONT) installed at the customer’s premises. The ONT converts the optical signal to an electrical one. The ONT is connected to the customer’s router using an RJ45 copper wire patch cord.
Optical network terminal—the PON port terminates the external fiber cable and the LAN ports connect to local routers or computers over RJ45 patch cords.
Geostationary Orbital Satellite Internet Access
A satellite -based microwave radio system provides far bigger areas of coverage than can be achieved using other technologies. The transfer rates available vary between providers and access packages, but 2 or 6 Mbps up and 30 Mbps down would be typical.
One drawback of satellites placed in a high geostationary orbit is increased latency.
To create a satellite internet connection, the ISP installs a very small aperture terminal (VSAT) satellite dish antenna at the customer’s premises and aligns it with the orbital satellite.
Because the satellite does not move relative to the dish, there should be no need for any realignment. The antenna is connected via coaxial cabling to a Digital Video Broadcast Satellite (DVB-S) modem.
Round Trip Time (RTT)
RTT is the two-way latency, or the time taken for a probe to be sent and a response to be received.
Low Earth Orbital Satellite Internet Access
Uses an array of satellites positioned in low Earth orbit (LEO). LEO satellites support bandwidth (around 70–100 Mbps at the time of writing) and latency (100–200 ms RTT). The drawback is that the satellites move relative to the surface of the Earth. The customer’s premises antenna must be provisioned with a motor so that it can periodically realign with the array. The dish construction uses a technology called “phased array” to connect to different satellites as they pass overhead and minimize the amount of mechanical realignment required. The antenna must have a clear view of the whole sky.
Fixed Wireless Internet Access
A wireless internet service provider (WISP) uses ground-based long-range fixed access wireless technology. The WISP installs and maintains a directional antenna to work as a bridge between the customer’s network and the service provider. A WISP might use Wi-Fi type networking or proprietary equipment and licensed or unlicensed frequency bands.
A fixed access wireless link is often low latency, or at least, lower latency than satellite. A disadvantage of fixed access wireless is that the actual unobstructed line of sight between the two antennas can be difficult to maintain. If the provider uses unlicensed frequencies, there are risks of interference from other wireless networks and devices.
All types of microwave radio link can be adversely affected by snow, rain, and high winds.
3G
A 3G cellular radio makes a connection to the closest base station. The area served by each base station is referred to as a “cell.” Cells can have an effective range of up to 5 miles (8 km), though signals can be obstructed by building materials. A 3G cellular radio typically works in the 850 and 1,900 MHz frequency bands
System for Mobile Communication (GSM)
Global System for Mobile Communication (GSM)-based phones. GSM allows subscribers to use a removable subscriber identity module (SIM) card to use an unlocked handset with their chosen network provider.
Code Division Multiple Access (CDMA)
Code Division Multiple Access (CDMA)-based handsets. With CDMA, the handset is directly managed by the provider and there is no removable SIM card.
