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Wide Area Network
Wiwin Sulistyo, ST, M.Kom
Packet-Switching vs Circuit-Switching
Networks
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Packet switching is used by the Internet and routed
networks
The path that is used to send data packets from one
point to another through routers is not
predetermined if there are multiple paths.
For example: you can see that from point A to point
B, there exist many paths and ways for packets to
travel between the source and destination PCs. If
we assume that each router is a LAN, which is not
shown, then it is possible for each LAN to
experience different bandwidth usage.
Packet-Switching vs Circuit-Switching
Networks
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Figure 7-1:Routed network
Packet Switching
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When a user at PC A wants to copy a shared file
from PC B, the data path is not a set path between
specific routers.
Packets will be sent from router to router based on
the quickest or shortest path.
If a router is extremely busy, it will not be used, and
a different path will be chosen if one exists.
Remember that other users are also sending data
packets over the same media and routers as you
are using.
Packet Switching
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Using Figure 7-1, let’s now look at an example of
how packet switching works:
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PC B will send its data to the router that is the least busy;
for the first data packet, let us assume that it is Router 6.
Now that Router 6 has the data packet, it will look at its
routing table and determine that Router 3 might be the best
way for it to reach PC A.
Router 6 sends the data packet to Router 3, which in turn
decides that the best path is to forward the packet on to
Router 1.
Router 1 will then send the packet to PC A.
Now, the second packet might be sent to Router 7,
because Router 6 has suddenly become very busy.
Packet Switching
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Router 7 will receive the data packet and forward it to Router 4, which
sends the packet to Router 3.
Router 3 checks its routing table and sends the packet to Router 2,
which in turn sends the packet on to PC A.
PC A will then start assembling the entire data file from the packets
received.
For the third data packet, let’s say that it is also sent to Router 7, which
will send it to Router 5 again.
Now let’s say that Router 2 has suddenly gone offline. Router 5 waits to
contact Router 2, but eventually times out and sends the data packet
back to Router 7, which then tries to send the data packet to Router 4.
Router 4 has since determined that Router 2 is offline, and sends the
data packet to Router 1.
Router 1 sends the data packet to PC A.
The fourth data packet is sent to Router 6, on to Router 3, then to
Router 1, and finally delivered to PC A.
Packet Switching
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Let’s look more closely at packets 3 and 4: While packet 3 was
detained at Router 5 because of the failure of Router 2, packet 4
was able to be delivered to PC A before the arrival of packet 3.
This shows that a packet-switched network is not dependent on
packets being delivered in the order in which they were sent.
Actually, if there are enough data paths, it is very common for
packets to be received out of order.
With routable protocols, data packets are numbered so they can
be placed back in the proper order to create the original block of
data that existed at the sending PC. It would do no good to
receive a jumbled database or unreadable document.
Circuit Switching
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Circuit switching, on the other hand, is the
foundation for the telephone system.
When you make a telephone call from your home to
someone next door or even 1000 miles away, a
circuit is opened between your telephone and the
telephone to which you are calling.
The circuit is not usable by others, so it is 100percent dedicated for your use. As you speak, your
voice is sent over the media to the other telephone
and is not broken up or rerouted.
One problem with circuit switching is when a circuit
fails.
Asynchronous Transfer Mode (ATM)
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Asynchronous Transfer Mode (ATM) is a
technology used mainly as a backbone in the
Internet world.
ATM technology is suitable for both LAN and
WAN connectivity.
With ATM technology in place for a LAN, it
will be easy to extend the technology to cover
a large area if needed, and make a WAN
without loss of performance.
Asynchronous Transfer Mode (ATM)
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ATM can be used to enhance broadband ISDN to
allow for the transmission of voice, data, and
multimedia packets over the same media
simultaneously.
ATM will provide for high bandwidth as needed if
enough users are implementing the bandwidth.
ATM bandwidth ranges from slow speeds, around
12.96 to 25 Mbps using copper media such as
category 3 UTP cable, and high speeds around
622.08 Mbps using fiber-optic cable.
With advances in technology, ATM speeds can
reach 2.488 Gbps.
Asynchronous Transfer Mode (ATM)
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ATM can be used with physical interfaces
such as FDDI and SONET/SDH, this means
that in an FDDI or SONET/SDH network,
ATM can be used on the network topology for
data transmissions.
Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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Synchronous Optical NETwork (SONET) is
an American standard that allows the unifying
of unlike transmissions into one single data
stream.
SDH is an international standard designed for
the same purpose as SONET.
Basically, SONET allows multiple companies
to transmit their packets on their network onto
a SONET backbone to be transmitted to a
remote location.
Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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Since many companies might be using different network
topologies and protocols, the data streams from each company
will most likely differ.
SONET allows these companies to transmit their information
over SONET without having to conform to a network standard.
For example, one company might have a 10-Mbps category-5
Ethernet network using IPX/SPX, while another is using fiber
optic with TCP/IP. These can then be combined into a single data
stream for transmission over one cable. More companies can be
added for transmission over the SONET medium without making
any changes to any of the company networks.
Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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SONET can be used as a backbone between
unlike systems.
This architecture allows for different media
types and transmission types to be combined
into one stream and sent over a fiber-optic
cable at a minimum speed of 54.84 Mbps for
SONET-1.
SONET is divided into electrical levels that
have varying speeds, termed synchronous
transport signals (STS).
Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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The highest level is SONET-192 with a speed
of 9953.280 Mbps.
SDH has no equivalent for SONET-1 at the
speed of 51.84 Mbps, but has a low speed of
155.520 Mbps mapping to SONET-3.
The different SDH levels are termed
synchronous transfer mode (STM). Table 7-1
lists the different levels.
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Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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The format for SONET is created by multiplexing all data signals into a
single data stream called a synchronous transport signal (STS).
The multiplexer is managed by the path terminating equipment (PTE)
from various different media and transmission types.
shown in Figure 7-2. Now that the STS signal is created, it must be
transmitted on the SONET media.
The STS transmission is managed by the line terminating equipment
(LTE), also shown in Figure 7-2. The LTE will send and receive the STS
signal on both ends of the SONET media. Remember that the STS
signal is in the form of electrical pulses. The SONET link might not be a
single connection from one point to another, and entire segment might
be comprised of sections of SONET media. Therefore, to create the
sections and have the entire segment appear as one physical link, you
use section terminating equipment (STE) to begin and end a section as
shown in Figure 7-3.
Synchronous Optical NETwork
/Synchronous Digital Hierarchy
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Figure 7-3:SONET/SDH link
Optical Carrier Level-X
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The Optical Carrier (OC) standard is used to specify
bandwidth for transmissions that are sent over fiberoptic cables.
These standards are equivalent to the SONET/SDH
standards and will correlate to the bandwidths
available for SONET/SDH.
One OC channel (OC-1) is 51.84 Mbps, as is STS-1.
When multiple channels are used, the bandwidth
increases. For example, nine OC channels (OC-9)
are comprised of nine OC-1 channels at 51.84 Mbps
each. This results in a total bandwidth of 9 x 51.84
Mbps, for a total bandwidth of 466.56 Mbps.
Frame Relay
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Frame Relay is an architecture that operates
at the OSI Physical layer and is independent
of all protocols being used over the medium.
Frame Relay is for transmitting data only
because the transmission speeds are not
always constant.
Since Frame Relay is not a constant speed,
real-time voice or video is impossible.
Frame Relay
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Frame Relay is a highly efficient method of
transmitting data using bandwidth at an optimum
level, allowing for bandwidths as high as 2 Mbps.
The nodes, which are used to route the frames in
the packet-switching network, each use a routing
algorithm that can help determine the efficiency of
the Frame Relay network.
Frame Relay does send frames as variable-length
packets that are not all set at the same size before
transmission.
Frame Relay
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If the bandwidth becomes too congested, Frame
Relay will drop any frames that it cannot handle.
Once the available bandwidth is at a minimum, the
source or destination can be notified to slow the
transmissions to avoid over-utilization of the
bandwidth, which will avoid packets being dropped
due to congestion.
Although the source or destination is requested to
slow the transmissions, the transmissions do not
necessarily have to slow.
Fiber Distributed Data Interface
(FDDI)
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The Fiber Distributed Data Interface (FDDI)
topology is sometimes referred to as a fast
redundant token ring network.
FDDI is similar to a token ring network, but
there are two rings and the media is fiberoptic cable operating at 100 Mbps.
If copper cable is used, such as category 5 at
100 Mbps, the topology is termed Copper
Distributed Data Interface (CDDI).
Fiber Distributed Data Interface
(FDDI)
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Two rings are used, the primary ring and the
secondary ring.
The primary ring is used at all times, and the
secondary ring is only used if the primary ring
fails.
The token is passed on each ring in opposite
directions; the reason for this will be apparent
shortly.
Fiber Distributed Data Interface
(FDDI)
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FDDI is specifically for WAN use and not for
LAN use.
FDDI is used to connect multiple sites.
Each building or office will have a dualattachment concentrator (DAC) that allows
both rings to be connected to the DAC, or two
single attachment concentrators (SAC).
The SAC will connect to a single ring,
allowing the SAC to be powered down
without affecting the ring.
Fiber Distributed Data Interface
(FDDI)
Fiber Distributed Data Interface
(FDDI)
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Functional FDDI
example
Tx/Ex-Carrier
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The T-carrier and E-carrier are both digital
mediums for which to transmit voice, data, or
images.
The T-carrier is used in the United States,
Japan, and Australia, whereas the E-carrier is
used in Europe, Mexico, and South America.
Tx/Ex-Carrier
Serial Line Internet Protocol dan
Point-to-Point Protocol
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SLIP dan PPP adalah dua protocol
komunikasi yang digunakan untuk
menghubungkan sebuah computer ke
jaringan yang jauh melalui koneksi serial
dengan menggunakan MODEM.
Sehingga memungkinkan sebuah computer
dapat menjalankan aplikasi-aplikasi jaringan
dari tempat dimana dia berada.
Dan protocol-protokol tersebut biasanya
digunakan untuk koneksi ke internet.
SLIP (Serial Line Internet Protocol)
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Merupakan protocol komunikasi yang
digunakan untuk membangun koneksi
dengan TCP/IP melalui sebuah serial
interface ke remote network.
Dirancang untuk berkoneksi dengan server
UNIX melalui saluran telepon, dengan DialUp.
Dan merupakan salah satu protocol pertama
yang memungkinkan koneksi ke remote
network melalui saluran telepon.
SLIP (Serial Line Internet Protocol)
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SLIP tidak menyediakan:
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Software compression
Password encryption
Multiple network protocol
Tidak menyediakan deteksi error pada saat
session setup
Alamat DHCP
Metode authentication
PPP (Point-to-Point Protocol)
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Merupakan protocol yang terletak pada lapisan
Data Link yang digunakan untuk enkapsulasi
paket dari network layer untuk dilewatkan melalui
jalur Synchronous dan Asynchronous.
PPP dirancang untuk:
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Encapsulasi paket-frame untuk pengiriman ke multiple
network layer melalui point-to-point link.
Network protocol multiplexing
Session negotiation
Data compressing negotiation.
Mendukung multiple protocok, antara laian: TCP/IP,
IPX/SPX, DECnet.
PPP (Point-to-Point Protocol)
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Untuk PPP yang mengirimkan data melalui serial
point-to-point link, menggunakan 3 komponen yang
saling melengkapi, antara lain:
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Protocol High Level data Link Control (HDLC), yang
melakukan enkapsulasi data pada saat ditransmisikan.
Protokol Link Control Protocol (LCP), yang melakukan
pembangunan, pengujian dan konfigurasi koneksi data link.
Bermacam-macam Network Control Protocol (NCP), yang
digunakan untuk konfigurasi pada protocol komuniasi yang
berbeda.
PPP (Point-to-Point Protocol)
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Prose kerja pada PPP
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PPP menggunakan 3 komponen diatas untuk melakukan komunikasi.
PPP awalnya akan mengirimkan frame LCP untuk pengujian dan konfigurasi
data link. Hal dilakukan untuk membangun link dan negoisasi, dimana ada
beberapa pilihan/opsi tambahan yang dibutuhkan untuk memudahkan
koneksi.
Selanjutnya melakukan negosiasi protokol authentication, dan biasanya
protokol yang digunakan adalah Challenge Handshaking Authentication
Protocol (CHAP) dan Password Authentication Protocol (PAP).
Selanjutnya client mengirimkan frame NCP untuk konfigurasi dan set up
protokol network layer yang digunakan pada sesi tersebut.
Setelah sesi diatas selesai, setiap protokol jaringan dapat melewatkan data
melalui koneksi tersebut. HDLC digunakan untuk melakukan encapsulasi
aliran data yang lewat melalui koneksi PPP.
Koneksi link masih aktif selama frame LCP atau NCP menutup koneksi, atau
terjadi error / external event seperti user mengakhiri link.
PPP (Point-to-Point Protocol)
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PPP Framing
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PPP frame menentukan format data yang
diencapsulasi sebelum dikirimkan ke jaringan.
PPP memberikan standard framing yang
memungkinkan koneksi ke bermacam-macam
standard server PPP karena semua vendor
menggunakan format yang sama.
PPP menggunakan HDLC sebagai dasar
encapsulation framing untuk koneksi serial.
PPP (Point-to-Point Protocol)
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Perangkat PPP
 PPP mampu beroperasi dengan beragam data terminal
equipment/data circuit terminating equipment (DTE/DCE).
 Contoh perangkat, standard EIA/TIA 232 (modem)
Authentication Protocols
 Protokol-protokol authentikasi : PAP, CHAP, MS-CHAP.
 Dengan protokol authentikasi kita bisa memberikan level security.
 Proses protokol authentikasi pada PAP:
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Protokol PAP bekerja sangat mirip dengan proses login client ke
server pada suatu jaringan jaringan.
Client melakukan authentikasi untuk dirinya dengan mengirimkan
username dan password ke server.
Server kemudian membandingkan inputan dari client tersebut
dengan informasi yang tersimpan pada dirinya.
Pada protokol autentikasi CHAP dan MS-CHAP memiliki cara
kerja tersendiri untuk melakukan proses autentikasi.
PPTP (Point-to-Point Tunneling
Protocol)
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Sebuah protokol jaringan yang menyediakan kemanan
transfer data dari remote client ke sebuah privat server
dengan menciptakan multiprotocol virtual private network
(VPN).
PPTP digunakan pada jaringan TCP/IP sebagai alternative
untuk metode dial-up.
System ini memungkinkan komunikasi yang aman pada
multiprotocol melalui suatu jaringan pablik, seperti internet.
PPTP sebenarnya ekstensi dari PPP, dimana PPP melakukan
encapsulasi paket PPP kedalam IP datagram untuk
ditransmisikan. Sehingga memungkinkan system yang
menggunakan PPP memiliki fitur-fitur keamanan yang
dimiliki oleh teknologi VPN.
PPTP (Point-to-Point Tunneling
Protocol)
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Cara kerja PPTP:
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VPN menyediakan tunnel melewati jaringan public
dengan jalur komunikasi yang aman.
PPTP dapat menentukan routing paket untuk
melewati jalur public secara aman menuju suatu
jaringan privat.
Tiga proses pada PPTP untuk membangun
koneksi dengan jalur yang aman. Dimana setiap
proses yang lengkap pada masing tahapan
secara berurutan, seperti dibawah ini:
PPTP (Point-to-Point Tunneling
Protocol)
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PPP connection and communication, PPTP
menggunakan PPP berkoneksi dengan remote network.
Setelah terkoneksi, PPP juga melakukan enkripsi paket
data yang dilewatkan antara remote host dan local
machine.
PPTP control connection, ketika sesi PPP sudah
terbentuk, PPTP menciptakan sebuah control koneksi
antara client dengan PPTP remote server. Proses
tersebut disebut dengan tunneling.
PPTP data tunneling, PPTP menciptakan IP datagram
PPP untuk dikirimkan. PPP mengenkripsi paket, yang
dikirimkan melalui tunnel ke PPTP server. PPTP server
kemudian mendekripsi paket PPP, mengurai IP
datagram, dan merutekan ke host yang dimaksud.
ISDN (Integrated Service Digital
Network)
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Sistem komunikasi telepon digital yang
memungkinkan melakukan transmisi data secara
simultan ujung ke ujung.
Dirancang untuk komunikasi dengan cepat,
digunakan untuk komunikasi small office dan home
user.
Ide dasar diawali tahun 1950, dikenalkan 1972.
Konsep dasar diawali dengan perkembangan
perangkat koneversi analog/digital pada pelanggan
yang memungkinkan layanan suara dan data
dikirimkan melalui jalur tungal.
ISDN (Integrated Service Digital
Network)
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ISDN Chanels:
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Sirkuit transmisi ISDN terdiri dari sekumpulan logika data
channel, sehingga memungkinkan data dan suara dibawa
lewat channel tersebut.
Dua tipe channel yang digunakan pada ISDN koneksi
tunggal:
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B channels (bearer channels):
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Memiliki Bandwidth 64Kbps per channel.
Spesifikasi B channel dijelaskan pada H channel, antara lain:
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H0384Kbps (6 B channels).
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H101472Kbps (23 B channels).
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H111536Kbps (24 B channels).
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H121920Kbps (30 B channels, the European standard).
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D channels (data channels):
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Menangani 16 Kbps (BRI) atau 64 Kbps (BRI)
Memungkinkan B channel melewatkan data dengan cermat.
Biasanya layanan ISDN berisi dua B channel dan sebuah D
channel.
Kelebihan-kelebihan dari ISDN:
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Kecepatan transmisi data yang lebih tinggi dibanding dial up.
Menyediakan multiple digital Channel pada saat yang bersamaan
untuk melewatkan data melalui jalur telepon regular.
Mendukung multiple device set up dalam satu link.
Koneksi lebih jelas karena data dikirimkan dalam format digital.
Karena ISDN menggunakan beberapa channel yang terpisah,
maka D channel digunakan untuk pensinyalan yang akan
menghilangkan administrative overhead. Sehingga semua
informasi yang dikirimkan dalam aliran bit.
PSTN (Public Switch Telephone
Network)
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Dirancang untuk system switching analog untuk
routing voice call
Menggunakan modem untuk berkoneksi ke
remote network melalui jalur PSTN
Bandwidth 56Kbps.