The document discusses the architecture of the Internet. It describes how the Internet consists of three main components: the network edge which contains end systems like clients and servers, the access network which provides physical transmission through wired or wireless links, and the network core which routes traffic between access networks. It then provides details on the different types of physical transmission media used in access networks including twisted pair cables, coaxial cables, fiber optic cables, power lines, and wireless technologies.

1. Computer Communication
Networks
3 - Internet Architecture
Instructor: Ashkan Farhangi
Email: ashkan.farhangi@ucf.edu

2. Outline
▪ Overview of the Internet
▪ Network Edge
▪ Access Network
▪ Network’s Core
2

3. Internet
mobile network
home network
enterprise
network
national or global ISP
local or
regional
ISP
datacenter
network
content
provider
network
Communication links
▪ Fiber, copper, radio, satellite
Hosts (end systems)
▪ Located at the edge of
Internet
Networks
▪ Collection of devices, routers,
links
3
Overview of the Internet
Routers, Switches
▪ Routers: Control the flow of data through
network
▪ Switches: Connect various devices
Routers Switches

4. Web-enabled toaster +
weather forecaster
Internet phones
Slingbox: remote
control cable TV
Security Camera
IP picture frame
Internet
refrigerator
Tweet-a-watt:
monitor energy use
sensorized,
bed
mattress
Amazon Echo
Pacemaker & Monitor
AR devices
Fitbit
Gaming devices
cars
scooters
bikes
Hosts (end systems)
▪ Hosts are located at the edge of Internet and have various application

5. 5
Routers
▪ Routers control the flow of data through the network
▪ Directs the traffic across the networks
▪ Connect multiple networks
▪ When routers receive a data, it can route the immediate or the final
destination
▪ If two routers that do not share a transmission line wish to
communicate, they must do this indirectly, via other routers
▪ The router allows the computer networks to communicate over large
distances

6. 6
Switches
▪ Switches can connect various devices to form a standalone network
▪ Send and receive data from the connected devices
▪ Suitable for enterprise and school environment where multiple
devices needs to be connected

7. Can switches function as
routers?

8. 9
Switches
Switches
▪ Switches can connect various devices to form a standalone network
▪ Send and receive data from the connected devices
▪ Suitable for enterprise and school environment where multiple
devices need to be connected
▪ Example: Two computers are connected through 1Gbps transmission
line to a local switch. The switch is connected to a router with a
100Mbps link
▪ What would be the speed of send/receive between two local
computers?

9. ▪ A global scale computer network consisting of interconnected
networks that use protocols to communicate
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The Internet
mobile network
home network
enterprise
network
national or global ISP
local or
regional
ISP
datacenter
network
content
provider
network
▪ Protocols define the format,
order of messages, and actions
(send, receive) among network
entities
• e.g., HTTP (Web), Skype, TCP,
IP, WiFi, 4G/5G, Ethernet
Ethernet
HTTP
Skype
IP
WiFi
4G
TCP
Streaming
video

10. A bigger network than the
Internet?

11. 13

12. Network Protocols
Hi
Hi
Got the
time?
2:00
time
HTTP connection
response
<Webpage>
HTTP connection
request
GET http://twitter.com/ucfcecs
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▪ Network protocols are defined as the standard procedure of computer
communication
▪ In particular, Protocols describe
▪ format of connection
▪ order of sent and received messages
▪ actions that must be taken on the transmission
▪ For example, compare a human protocol and a computer network protocol:

13. ▪ The internet infrastructure contains 3 main components
▪ Network Edge
▪ Access Network
▪ Network Core
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Internet Infrastructure
Network Edge Access Network Network Core

14. Network Edge
Network edge contains hosts such as clients and servers
▪ Clients are widespread around the globe
▪ Servers are typically located in
data centers for security and efficiency
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mobile network
home network
enterprise
network
national or global ISP
local or
regional ISP
datacenter
network
content
provider
network

15. Access network
▪ Access network provide physical transmission through wired or wireless
transmission links
▪ Type of Access Networks:
▪ Residential access nets (WiFi)
▪ Institutional access networks (WLAN)
▪ Mobile access networks (5G)
▪ …
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mobile network
home network
enterprise
network
national or global ISP
local or
regional ISP
datacenter
network
content
provider
network

16. Access networks and physical media
▪ Access networks are categorized as a guided media:
▪ signals propagate in solid media: copper, coax, fiber
▪ Or as an unguided media:
▪ signals propagate freely, e.g., radio
▪ Various frequencies of the electromagnetic spectrum is used to share a
wire or wireless transmission line
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17. ▪ Twisted pair consists of two insulated wires gently twisted together
▪ Four such pairs are typically grouped in a plastic sheath to protect the
wires and keep them together
▪ Two insulated copper wires(effective 300 feet)
• Category 5: 100 Mbps (Bandwidth 100 MHz) (1995)
• Category 5e: 1 Gbps Ethernet (Bandwidth 100 MHz) (1999)
• Category 6: 10 Gbps Ethernet (Bandwidth 250 MHz) (2002)
• …
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Twisted Pair Cable

18. Coaxial cable
▪ Coaxial cable contains copper core to provide a guided transmission
▪ We can transmit data in different channels through various frequency bands
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cable
modem
splitter
…
cable headend
Channels
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1 2 3 4 5 6 7 8 9

19. The function of braided outer
conductor?

20. Can’t we use our
power lines to
connect to the
Internet?
💻

21. Power Lines
▪ It seems practical to send and receive data with our power lines
▪ For example, a TV and a receiver are plugged into the wall, which must be
done anyway because they need power. Then its possible to send and
receive video signal over the electrical wiring
▪ Pros:
▪ Already implemented infrastructure of power lines to buildings
▪ Cons:
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22. Power Lines
▪ It is practical to send and receive data with our power lines.
▪ For example, a TV and a receiver are plugged into the wall, which must be
done anyway because they need power. Then its possible to send and
receive video signal over the electrical wiring
▪ Pros:
▪ Already implemented infrastructure of power lines to buildings
▪ Cons:
▪ Not designed for data transmission, power signals are sent at 50–60 Hz and
power lines are designed to distribute power signals
▪ Electrical wirings are susceptible to external noise (electric & magnetic fields)
▪ Switching on the home appliances can create electrical noise over a wide
range of frequencies = error in higher frequencies (e.g., MHz for internet)
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23. 27
Fiber Optic Cable
▪ Fiber optic cable uses a core glass fiber to carry light pulses (e.g., laser or
LED) where each pulse is seen as a “bit”
▪ Provides high-speed point-to-point transmission (10’s-100’s Gbps)
▪ Benefits from low error rate due to its immunity to electromagnetic noises
▪ Components:
▪ Outer jacket provides a general protection of cable
▪ Strength Member is used to protect the fiber core from physical forces
▪ Coating is used to absorb shocks and prevents bending
▪ Cladding is used as a thin layer of glass fiber to reflect light back to the core
▪ Core consist of a fiber glass tube to transmit laser or LED signal

24. Theoretically, what
would be the maximum
transmission speed of a
fiber optic?

25. cable
modem
splitter
…
cable headend
data, TV transmitted at different
frequencies over shared cable
distribution network
cable modem
termination system
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Wired: cable-based access
▪ Hybrid Fiber Coax combines both that combines optical fiber
and coaxial cable
▪ up to 40 Mbps – 1.2 Gbps downstream transmission rate, 30-
100 Mbps upstream transmission rate

26. Wireless Physical Media
Wireless radio
▪ Signal carried in various
“bands” in electromagnetic
spectrum
▪ No physical “wire”
▪ Environment effects:
• reflection
• obstruction by objects
• Interference/noise
Radio link types:
▪ Wireless LAN (WiFi)
• 10-100’s Mbps; 10’s of meters
▪ Wide-area (e.g., 4G cellular)
• 10’s Mbps over ~10 Km
▪ Bluetooth: cable replacement
• short distances, limited rates
▪ Microwave
• point-to-point; 45 Mbps channels
▪ Satellite
• up to 45 Mbps per channel
• 270 msec end-end delay
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27. Wireless Access Networks
Shared wireless access networks connect end system to router
via base station (access point)
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Wireless local area networks
(WLANs)
▪ typically within or around
building (~100 ft)
▪ 802.11b/g/n (WiFi): 11, 54, 450
Mbps transmission rate
to Internet
to Internet
Wide-area cellular access
networks
▪ provided by mobile, cellular
network operator (10’s km)
▪ 10’s Mbps
▪ 4G/5G cellular networks

28. Digital Subscriber Line (DSL)
▪ Use existing telephone line provided by telephone companies
• data over DSL phone line goes to Internet
• voice over DSL phone line goes to telephone net
▪ 24-52 Mbps dedicated downstream transmission rate
▪ 3.5-16 Mbps dedicated upstream transmission rate
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central office telephone
network
voice, data transmitted
at different frequencies over
dedicated line to central office
DSL
modem
splitter

29. Home Networks
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to/from headend or
central office
cable or DSL modem
router
wired Ethernet (1 Gbps)
WiFi wireless access
point (54, 450 Mbps)
Wireless and wired
devices
often combined
in single box

30. Access networks: enterprise
networks
▪ Companies, universities, etc.
▪ Mix of wired, wireless link technologies, connecting a mix of switches
and routers
▪ Ethernet: wired access at 100Mbps, 1Gbps, 10Gbps
▪ WiFi: wireless access points at 11, 54, 450 Mbps
Ethernet
switch
institutional mail,
web servers
institutional router
Enterprise link to
ISP (Internet)
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31. Access Networks: Data Centers
▪ high-bandwidth links (10s to 100s
Gbps) connect hundreds to thousands
of servers together, and to Internet
mobile network
home network
enterprise
network
national or global ISP
local or
regional ISP
datacenter
network
content
provider
network
Courtesy: Massachusetts Green High Performance Computing
Center (mghpcc.org)
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32. Host: sends packets of data
host sending function:
▪ takes application message
▪ breaks into smaller chunks,
known as packets, of length L bits
▪ transmits packet into access
network at transmission rate R
• link transmission rate (link
capacity or bandwidth) R: link transmission rate
host
1
2
two packets,
L bits each
packet
transmission
delay
time needed to
transmit L-bit
packet into link
L (bits)
R (bits/sec)
= =
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33. Example
▪ An internet service provider (ISB) advertises 1Gb/s internet speed to the
customers
▪ What would be the packet transmission delay of receiving 1000 packets each with
a 10KB size? (use the actual Byte)
▪ What would be the maximum number of packets that can be sent 10 seconds?
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packet
transmission
delay
time needed to
transmit L-bit
packet into link
L (bits)
R (bits/sec)
= =

34. Reference
▪ Computer networks 5th Edition by Tanenbaum, A.S. and Wetherall, D.
▪ Computer Networking: A Top-Down Approach 7th Edition by Kurose, J. and
Ross, K.
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