Lesson 1 Flashcards
Is a worldwide system of computer networks
Internet
A network of networks
Internet
Hosts = ___________
End Systems
Communication Links
Fiber, copper, radio, satellite
Transmission rate of Communication Links
Bandwidth
a measurement indicating the maximum capacity of a wired or wireless communications link to transmit data over a network connection in a given amount of time.
Network bandwidth
is used to forward packets (chunks of data)
Packet Switches
Hardware in Packet Switching
Routers and Switches
connects multiple devices to create a network
Switch
connects multiple switches, and their respective networks, to form an even larger network.
Router
- IP picture frame
- Web enabled toaster
- Internet refrigerator
- Sensorized bed mattress
- Internet Phones
- Tweet-a-watt monitor energy use
Examples of “Fun” Internet-connected devices
Internet
” network of networks “
Interconnected ISPs
Internet
control sending, receiving of messages
Protocols
Example of Protocols
- TCP
- IP
- HTTP
- Skype
- 802.11
Example of Internet Standards
- RFC
- IETF
Services that the Internet provides
- Infrastructure that provides services to applications
- Provides programming interface to apps
Web
VoIP
Email
Games
E-commerce
Social nets
Infrastructure that provides services to applications
Hooks that allow sending and receiving app programs to “connect” to internet and Provides service options, analogous to postal service
Provides programming interface to apps
are defined format, of message sent and received among network entities, and actions taken on message transmission, receipt
Protocols
exchanging messages and taking actions in human
Human Protocol
the entities exchanging messages and taking actions are hardware or software components of a computer network
Network Protocols
All communication activity in Internet governed by _____________.
protocols
Example of Human Protocol
Greetings like “Hi” and “ Hello”
Network Structure
- Network Edge
- Access networks, Physical Media
- Network Core
Network Edge
Hosts: Clients and servers often in data centers
Access networks, Physical Media:
Wired, and wireless communication links
How to connect end systems to edge routers?
- Residential access nets
- Institutional access networks (School and company)
- Mobile access networks
Bandwidth unit measurement
BPS/ Bits per second
refers to internet connection where you have exclusive access to the connection infrastructure
Dedicated Network
Means your internet connection uses the same infrastructure as your neighbors
Shared Network
Digital Subscriber Line (DSL)
is a type of network connection that uses existing telephone line to central office DSLAM
Data over DSL phone line goes to ________
Internet
Where does the Voice over DSL phone line go?
telephone net
Frequency division multiplexing
The different channels are transmitted in different frequency bands
Asymmetric: up to 30 Mbps downstream transmission rate, 2 Mbps upstream transmission rate
HFC: Hybrid Fiber Coax
The network of cable, fiber attaches homes to ISP router
HFC
Does DSL has dedicated access to central office?
Yes
Wireless Devices -> Wireless Access Point -> Router, Firewall, NAT -> Wired Ethernet Connected to router -> Cable or DSL Modem -> Central Office
Home Network Connections
ENTERPRISE ACCESS NETWORKS (ETHERNET)
- Typically used in companies, universities, etc.
- 10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps transmission rates
- Today, end systems typically connected into Ethernet Switch
EXAMPLES OF WIRELESS ACCESS NETWORKS
- Wireless LANs
- Wide-area wireless access
- Within a building (100 ft.)
- 801.1 1b/g/n (WiFi): 11,54,450 Mbps transmission rate
Wireless LANs
- Provided by telco (cellular)
- Between 1 and 10 Mbps
- 3G, 4G: LTE
Wide-area wireless access
Shared wireless access network connects end systems to router
WIRELESS ACCESS NETWORKS
- Takes application message
- Breaks into smaller chunks, known as packets, of Length L bits
- Transmits packet into access network at transmission rate R
Host sending function
Physical Media: Propagates between transmitter/receiver pairs
Bit
Physical Media: What lies between transmitter & receiver
Physical Link
Physical Media: Signals propagate in solid media: copper, fiber, coax
Guided Media
Physical Media: Signals propagate freely
e.g., radio
Unguided Media
Physical Media: Two insulated copper wires
Twisted Pair (TP)
2 Twisted Pair cable categories
- Category 5
- Category 6
TP Category: 100 Mbps, 1 Gbps Ethernet
Category 5
TP Category: 10 Gbps
Category 6
Physical Media: Types of Cable
- Coax cable
- Fiber optic cable
- Two concentric copper conductors
- Bidirectional
- broadband:
Coax cable
- Glass fiber carrying light pulses, each pulse a bit
- High-speed operation
- Low error rate
Fiber optic cable
- Signal carried in electromagnetic spectrum
- No physical “wire”
- Bidirectional
Radio
Propagation environment effects of Radio Transmission
- Reflection
- Obstruction by objects
- Interference
Mesh Interconnected routers
Network Core
RADIO LINK TYPES:
- Terrestrial Microwave
- LAN
- Wide-area
- Satellite
Packet-switching
hosts break application-layer messages into packets
PACKET-SWITCHING: STORE-AND-FORWARD
entire packet must arrive at router before it can be transmitted on next link
PACKET-SWITCHING: QUEUEING DELAY AND LOSS
Packets will queue, wait to be transmitted on link. Packets can be dropped (lost) if memory (buffer) fills up
TWO KEY NETWORK-CORE FUNCTIONS
- Routing
- Forwarding
Determines source-destination route taken by packets
ROUTING
Moves packets from router’s input to appropriate router output
FORWARDING
End-end resources allocated to reserved for “call” between source & dest
CIRCUIT SWITCHING
Allows more users to use network
Packet-Switching
it works with digital signals as well as analog signals
Time division multiplexing (TDM)
It works with only analog signals.
(FDM) Frequency division multiplexing
How many users can accommodate in Circuit Switching?
10 Users
How many users can accommodate in Packet Switching?
With 35 users, probability > 10 active at same time
Private network that connects its data centers to internet, often by passing tier-1, regional ISPs
Content Provider Network
(Packets queue in router buffers)
- Packet arrival rate to link (temporarily) exceed output link capacity
- Packets queue, wait for turn
HOW DO LOSS AND DELAY OCCUR
FOUR SOURCES OF PACKET DELAY
- Nodal processing
- Queueing delay
- Transmission delay
- Propagation delay
Source of Packet Delay:
1.Check bit errors
2. Determine output link
3. Typically <msec
Nodal Processing
Source of Packet Delay:
1. Time waiting at output link for transmission
2. Depends on congestion level of router
QUEUEING DELAY
Source of Packet Delay:
1. L: packet length (bits)
2. R: link bandwidth (bps)
Transmission Delay
Source of Packet Delay:
1. d: length of physical link
2. S: propagation speed ( ~ 2x 10 ^8 m/sec
Propagation Delay
It provides delay measurement from source to router along the end-end Internet path towards destination.
TRACEROUTE PROGRAM
Queue or also known as buffer, is a preceding link in a buffer that has finite capacity.
Packet Loss
Packet arriving to full queue dropped or also known as __________
Loss
Lost packet may be retransmitted by previous node, by source end system, or not at all
Packet Loss
Throughput
Bits are transferred between sender or receiver
Throughput: rate at a given point in time
Instantaneous
Throughput: is a rate over long period of time
Average
Bottleneck Link
link on end-end path that constrains end-end throughput
Networks are complex with many __________
Pieces
- Hosts
- Routers
- Links of various media
- Applications
- Protocols
- Hardware, software
” Pieces “ of Networks
each ________ implements a service
layer
Layering
it helps to deal with complex systems
INTERNET PROTOCOL STACK
- Application
- Transport
- Network
- Link
- Physical
Protocol Stack: Application
Supporting network applications
Protocol Stack: Transport
process -process data transfer
Protocol Stack: Network
Routing of datagrams from source to destination
Protocol Stack: Link
Data transfer between neighboring network elements
Protocol Stack: Physical
Bits “on the wire”
FTP, SMTP, HTTP
Example of supporting network applications
TCP, UDP
Examples of Process-process data transfer
ISO/ OSI REFERENCE MODEL
- Application
- Presentation
- Session
- Transport
- Network
- Link
- physical
Allow applications to interpret meaning of data
- e.g., encryption
- Compression
- Machine-specific conventions
Presentation
Synchronization, checkpointing, recovery of data exchange
Session
SOURCE ( Flow )
Message -> Segment -> datagram ->
frame
the protection of the underlying networking infrastructure from unauthorized access, misuse, or theft
NETWORK SECURITY
Enumerate what Bad Guys can do
- PUT MALWARE INTO HOSTS VIA INTERNET
- ATTACK SERVER, NETWORK INFRASTRUCTURE
- CAN SNIFF PACKETS
- CAN USE FAKE ADDRESSES
Malware can get in host form:
- Virus
- Worm
Self-replicating infection by receiving or executing object
Virus
Example of Virus
Email Attachment
Self-replicating infection by passively receiving object that gets itself executed
Worm
Can record keystrokes, websites visited, and upload information to collection site
Spyware malware
Infected host can be enrolled in ______, used for spam.
botnet
Attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
Denial of Service (DoS)
- Select target
- Break into host around the network (see botnet)
- Send packets to target from compromised hosts
Process of DoS
a method of detecting and assessing packet data sent over a network.
Packet Sniffing
- Broadcast media
- Promiscuous network interface reads/records all packets passing by
Packet “ Sniffing “
Send packet with false source address
IP Spoofing
Types of Defense in Network Security
- Access control. This method limits access to 2. network applications and systems to a specific group of users and devices. …
- Antivirus and antimalware. …
- Application security. …
- Behavioral analytics. …
- Cloud security. …
- Data loss prevention (DLP). …
- Email security. …
- Firewall.
