Teleworker Services

Organizations can take advantage of having their employeer working away from the office. It's quite possible now with the advance of broadband and wireless technology. Data, video and real-time applications can be transferred and distributed across the networks.

security, cost-effective and reliable are top priorities in an organization. with the growing number of teleworkers, enterprises must choose the right technology for connecting people in home offices (SOHOs), small offices or any other remote locations. three technologies that might be used are:

  • WAN layer 2 technologies, including Frame Relay, ATM and lease dlines. the security of these services depends on the service provider.

  • IPsec VPN, offer flexible and scalable connectivity.

  • Site-to-site connections, this is the most common used technology for connecting teleworkers. combined with the technology of VPN over the public internet, this can create a secure, cost-effective and reliable connenction.

to connect teleworkers with the organization's network, components on both sides are needed. the components might be:
  • Components at workers. a laptop/pc, a VPN router or a VPN client software installed, and a broadband connection (DSL, cable).

  • Components at corporate. VPN-capable router, VPN concentrators, security appliances, and central management devices for resilient aggregation and termination of the VPN connections.

  • soon VoIP and teleconferencing could become a component for the teleworkers connectivity. but these requirements would need upgrade to the technology such as QoS.

    Services Available for Teleworkers
    offered by cable television service providers. this cable system use coaxial cable that carries Radio Frequency (RF) to carry signals across the network. the internet signals is carried through the same coaxial cable with the television signals. a special modem is used to seperate those signals.

    Radio Waves constitue a portion of the electromagnetic wave spectrum between 1 kilohertz (kHz) and 1 terahertz. Each TV station has each own frequency over this spectrum. the same applies to a cable network. the scope of the frequencies used in cable network are:
  • Downstream. traffic from the provider to subscribers. downstream frequencies are in the range 50 to 860 megahertz (MHz).

  • Upstream. traffic from subscribers to the provider. upstream frequencies are in the range of 5 to 42 MHz.

  • Data-over-Cable Service Interface Specification (DOCSIS) is an international standard developed by CableLabs, a reasearch, non-profit and development consortium for cable-related technologies. it certifies cable equipments from vendors such as cable modem and cable model termination system. devices from cable vendors must pass the test conducted by CableLabs. DOCSIS defines the communications and operation support interface requirements for a data-over-cable system. DOCSIS specifies the OSI layer 1 and 2 requirements
  • Physical layer. DOCSIS specifies the wdith of the channel (bandwidth) and the modulation techniques used to carry the RF signals. it could be 200kHz, 400kHz, 800kHz, 1.6MHz, 3.2MHz and 6.4MHz.

  • MAC Layer. DOCSIS defines the access method, such as time-division multiple access (TDMA), frequency-division multiple access (FDMA) or synchronous code division multiple access (S-CDMA).

  • as stated above that downstream and upstream use different frequencies. the devices required to send upstream and downstream in a cable system are also different. Cable Modem Termination System located at the subscriber to send RF over the cable system, while Cable Modem located at the subscribers. the CMTS communicates with CMs, the architecture of the network can consists of optical fiber mixed with the coaxial cable. fiber cables are used to connect the subscriber headend with some nodes (used to converts optical signals to RF signals) forming a web of fiber trunk cables. then coaxial cables are used to connect the subscribers to the node. every subscribers share the upstream and downstream bandwidth in a network segment of cable system. the actual bandwidth in a CATV line can be up to 27mb/s for downstream and 2.5 mb/s for upstream.

    DSL (Data Subscriber Link)
    over years, copper lines are used for transferring voice communication only. actualy the bandwidth needed to carry a voice conversation over copper lines is 300Hz to 3KHz. DSL technology uses the upper bandwidth from 3kHz up to 1MHz to transfer high-speed data services over ordinary copper lines. two basic types of DSL are asymmetric DSL (ASDL) and symmetric DSL (SDSL). each type has many further varieties. ADSL provides higher bandwidth for downstream traffic than upstream traffic. while SDSL provides the same capacity. Unlike cable system, the subscriber must be in less than 5.5 kilometers from the loop. the advantage of DSL over cable system is that DSL is not a shared medium, every subscribers use a seperate direct connection.

    devices needed for a DSL connection are:
  • Transceiver. located at the subscriber end. usually this is a DSL modem.

  • DSLAM. DSL access Multiplexer. this is located at the central office of the provider. this will combines (multiplexing) individual DSL connections from users into one high-capacity link to an ISP.

  • one advantage of ADSL is the ability to use POTS voice service and high-speed data service simultaneously. in order to achieve this, voice and data traffic must be seperated. two ways to seperate ADSL signals from voice transmission are using a microfilter or a splitter
  • microfilter. microfilter is a passive low-pass filter with two ends. one end connects to the telephone and the other end connects to the telephone wall jack.

  • POTS splitter. POTS splitter is a passive device that seperates the ADSL signals from voice traffic. Splitter can be located at the provider or at the subscriber end. a splitter has three ends. one connects to the telephone, one connects to the ADSL modem and the other to the wall jack.

  • Wireless / Stelite
    DSL and cable require teleworkers to connect their PCs with a cable either ethernet or coaxial cable. wireless/wi-fi doesn't need it. other thing that makes wi-fi easy to be installed is that it uses unlicensed radio spectrum, most TV and radio station use transmission that require a license to use. and since the beginning of 2007, wireless adapter is becoming cheaper and that many computer manufacturers start building wireless adapter into their laptop computers.

    recently, the main challenge of wireless is the limited area covered by a wireless router or wireless acess point. however, with advances of technology, the area covered can be extended. multiple access points can be used together to form one large covered area. new development in broadband wireless technology increase the wireless availability including Municipal wi-fi, WiMax and satellite internet. WiMax offers greater area and higher speed than Wi-Fi.
    a WiMax network consists of two main components:
  • a tower similar to a cellular telephone tower in concept. a single WiMax tower covers a 3000 square miles area.

  • a WiMax receiver, this similar to wifi adapter in laptop or PC.

  • satellite internet services are used where land-based internet service is not available. satellite internet can be used for vessels at sea, airplanes in flight and vehicles on land. three way to connect to internet using satelites are:
  • one-way multicast satellite internet system, used for IP multicast based data such as data, video or audio distribution. full interactivity is not possible.

  • one-way terrestrial return satellite internet system, use traditional dialup access to send data through a modem and download data from the satellite.

  • two-way satellite internet, sends data from remote sites to a hub via satellites, from the hub, data will be sent to the internet. each satellite requires precise positioning to avoid intereference with other satellites.