Download konsep dan komunikasi data dalam wan

Universitas Mercu Buana
Jaringan Komputer
Week 10
KONSEP DAN KOMUNIKASI DATA
DALAM WAN
Kemampuan akhir yang di harapkan adalah
•
Mampu memahami dan menjelaskan cara pengiriman komunikasi data dalam WAN
•
Mampu memahami konsep frame relay
Materi :
10.1 Introduction WAN and Backbones
10.2 What Is a WAN?
10.3 Circuit Switching Networks
10.4 The Public Switched Telephone Network
10.5 Digital Subscriber Line
10.6 Synchronous Optical Networking
10.7 SONET architecture
10.1 Introduction WAN and Backbones
Wide Area Network, or WAN, is a collection of networks connected through a public service
or covering a large geographical area. To enable a WAN requires a routing or switching
technology and a set of protocols that create paths from one point to another. There are four
kinds of WANs: circuit switching, packet switching, cell relay, and leased lines. The Public
Switched Telephone Network (PSTN) is used as an example of a circuit switching network.
The PSTN is built hierarchically. Different methods for connecting to the PSTN for data
services are described. In particular, two of the most popular connection types, ISDN and
DSL, are described in detail. The backbone technologies for connecting networks are
through T and E-carrier networks. Different standards and grades exist, and the higher
speed grades require optical fiber cables. SONET/SDH is the most popular protocol for data
transfer on these backbones. Data that flows over SONET can be in the form of
Asynchronous Transfer Mode (ATM) or Packet over SONET (PoS).
Packet switching networks define endpoints but not the routes. IP networks are built from
packet switching, with the Internet being the prime example. Protocols such as X.25, Frame ,
these WAN links are secure, often fast, and tend to be expensive. Lease lines use Data Link
protocols as their control mechanisms.
2012
1
Jaringan Komputer
Johanes Fernandes Andry, S.T, M.Kom
Pusat Bahan Ajar dan eLearning
http://www.mercubuana.ac.id
Universitas Mercu Buana
Jaringan Komputer
Week 10
10.3 Circuit Switching Networks
Circuit switching networks were the first type of WANs to be widely used. They arose from
networks that carried voice communication, were analog, and generally involved low data
throughput. The telephone system is the best example, but even earlier, you could consider
telegraph lines to be a circuit switching network. Circuit switching networks today transfer
both analog and digital data through a defined connection path. A network can also assign
circuits to individual paths to an endpoint; that kind of network is referred to as a dedicated
circuit network, as shown on the right in Figure 10.1. Alternatively, a network can create
circuits as required from a set of available potential connections, which is referred to as a
virtual circuit network (as shown on the left in Figure 10.1). The dedicated circuit is a set of
defined stateful connections, whereas the virtual circuit creates circuits on the fly and tears
them down when the data is passed through those connections.
Figure 10.1 shows the difference between these two network types. LANs can connect to the
service provider using modems, multiplexers, channel service units (CSUs), or data service
units (DSUs). CSUs and DSUs are network interfaces to the WAN.
Figure 10.1 Virtual circuits versus dedicated circuits in a circuit switching network
2012
2
Jaringan Komputer
Johanes Fernandes Andry, S.T, M.Kom
Pusat Bahan Ajar dan eLearning
http://www.mercubuana.ac.id
Universitas Mercu Buana
Jaringan Komputer
Week 10
Figure 10.2 The original AT&T network system architecture
10.5 Digital Subscriber Line
Digital Subscriber Line, or DSL (originally Digital Subscriber Loop), is one of the most
popular methods in use today for connecting to the Internet through the phone system,
rivaled only by cable modems offered by digital cable TV networks, and perhaps WiMax
(802.16) in the future. DSL was introduced in 1998 and has largely replaced ISDN.
The most common version of DSL in use is Asymmetric DSL (ADSL), but occasionally
Symmetric DSL is encountered. ADSL operates at anywhere from 256 Kbits/s up to 6.31
Mbits/s, the speed of which is a function of the level of service you purchase from a provider
and the line condition. Speeds are more typically found in a range between 512 Kbits/s and
1.54 Mbits/s for downloads and 128 Kbits/s for uploads.
2012
3
Jaringan Komputer
Johanes Fernandes Andry, S.T, M.Kom
Pusat Bahan Ajar dan eLearning
http://www.mercubuana.ac.id