CS 356 - Introduction to Computer Networks
How to define a zone
3-4 zones per region, individual network centers
Pipelining
Allows parallel TCP connection to server
Average Queuing Delay
Amount of delay for the individual packets divided by the amount of packets
Global ISP
Attempts to provide internet to every access network
TCP uses
humilitive ack
Probability of user p transmitting
p^k(1-p)^(120-k)(120 choose k)
Packet-Switched Networks
Destination address in packet header Message is broken into chunks (packets) Transmitted as Full R of a Link
Header vs Payload
First section of each data packet vs the rest
Different HTTP Request Methods
GET POST HEAD PUT DELETE
Non persistent HTTP
Initiate TCP connection Request file Time to transmit file File received
Traffic Intensity
La/R a: units of packets@ queue/sec L: size of each packet
Benefits of Cloud Computing
On demand self-service Brod network access Resource pooling Rapid elasticity Measured service
Formula for Throughput
R/N bps
RTT
Round Trip Time or Real Transfer Time
DNS Security Extensions (DNSSEC)
Secured version of DNS
Data Center
Server storage with stacks
Anycast
Single sender to one of many possible receivers
Unicast
Single sender to single receiver
Multicast
Single sender to some specified group of receivers
Malware
Virus Worm Trojan horse Spyware
IP Spoofing
When an intruder uses another site's IP address to masquerade as that other site
Temporal coding
Subtracts the difference and only edits associated values
Features of regions - small consumers
Subzone (1-a, 1-b, etc.) External IP Address Access Virtual Machines Storage Disks
Choose the BEST answer: The ______ acknowledges bytes up to the ______ missing byte in the stream of bytes.
TCP receiver, first
HTTP Version
1.0 + 1.1 [!]
Local name servers cache TLD, IP addressed How long does it take for a hostname IP address to update?
2 days
200 301 400 404 505
200 OK 301 Moved Permanently 400 Bad Request 404 Not Found 505 HTTP Version Not Supported
Regional ISP
A smaller ISP that connects specific regions to larger ISPs
Select TWO that apply: A worm like Morris Worm must need which of the following to multiply and propagate: A. A protocol that allows access a remote host B. A network program to attach itself to C. A end user's interaction such as clicking D. A daemon which constantly run in a host
A. A protocol that allows access a remote host D. A daemon which constantly run in a host
Choose the best answer: End Systems are connected to the _______ to connect to the internet in a local area network. A. Edge router B. Ethernet C. Core router D. Cloud
A. Edge router
HTTP3
Adds security Per object error Congestion control More pipelining
Services/Functions
An infrastructure that provides services to Internet applications
Access Networks
Areas where individuals can access the internet
Traceroute helps us witness ______ A. The bottle neck link identification process B. Actual Internet delay and loss at the moment C. The round trip of three probes to all routers on the path to destination without fail D. The internet protocol stack from source to destination
B. Actual Internet delay and loss at the moment
Choose ALL that apply: The web is considered a better choice to share content than traditional radio and TV broadcast channels for: A. its infrastructure B. its content formats C. its availability D. its client server architecture
B. its content formats C. its availability
Store and forward transmission
Bits cannot be sent by themselves Bits must be sent as a whole package
Digital signature is a mathematical scheme for demonstrating the authenticity of digital messages or documents. It is a part of the practice of A. Access restriction B. Authentication C. Integrity checks D. Confidentiality
C. Integrity checks
With regard to the internet architecture, where does the complexity of this implementation lie? A. Network core b/c this is a core internet function between a client-server architecture B. Network core b/b the traffic mostly concentrates within the network core C. Network edge b/c this is implemented at servers whose presences are always at the edge of the network D. Network edge b/c the traffic mostly concentrates at the network edge
C. Network edge b/c this is implemented at servers whose presences are always at the edge of the network
Centralized vs. Distributed DNS
CENTRALIZED: If someone has access to the server with the information, any data can be added, modified and deleted. DISTRIBUTED: All data is distributed between the nodes of the network.
Radio Channels
Carry signals with Electromagnetic Spectrum - Short distance - LAN (1skm) - WAN (10skm)
Phase Modulation
Changes the phase of the waves
Amplitude Modulation
Changes the size of the waves
Frequency Modulation
Changes the wavelength of the waves
Internet Exchange Point (IXP)
Connects ISPs
Propagation Delay
Constant rate unaffected by volume Time for one bit to go across the link
Choose ALL that apply: HTTP A. is a protocol that provides privacy and data integrity B. the semantics C. is a client-server protocol where either of the hosts involve can act as client or server depending on their needs D. is a protocol to fetch resources such as HTML documents and their reference objects
D. is a protocol to fetch resources such as HTML documents and their reference objects
Choose the BEST answer: To establish the lower bound for the distribution time of a file to all participating hosts, we need to know: A. the maximum download rates B. the format of the files involved C. the paths among the hosts involved D. the architecture of the network apps involved
D. the architecture of the network apps involved
Recursive vs. Iterative
DNS asked party handles everything recursively and returns to itself Iterative goes one by one through DNS servers asking parties one by one
TLS (Transport Layer Security)
Data integrity Encrypt TCP connection End point authentication
Circuit-Switched Networks
Dedicated circuit Guaranteed constant rate Individual paths per circuit
Bandwidth Delay
Delay caused by the rate of bits being limited by the number of bits allowed to pass through the link
Host
End systems running network apps at Internet's "edge" Host applications and software
Ways to Attack DNS
Enter cache and change information to redirect traffic Pretend to be listed sites Attack root to access hierarchy Overwhelm DDoS Man in the middle to redirect/DNS poisoning
Store-and-forward transmission causes queuing delay.
False
True or False: In client-server architecture, for a server to distribute F bits to n clients, the load of the server is to be at least the load of each client (i.e. F) which download F and at most the total load for all clients (i.e. nF).
False
Unlike fiber-optic cable, unshielded twisted pair is a form of unguided physical media.
False
The Date: header in the HTTP response message indicates when the object in the response was last modified.
False, when the HTTP request was sent
Cloud Networking Product - Secure
Frequency of traffic and intentions, awareness of application protocols, establishment of network telemetry
ISP
Internet Service Provider
DNS Order
Local Root Local TLD Local Authoritative User
TCP Timeout
Longer than RTT Too short = premature timeout, unnecessary retransmissions Too long = slow reaction to segment loss
Bandwidth Delay Product
Maximum number of bits that can be in the link at one time
Delays in a Packet Switch Network
Packet loss Routing Up and download Transmission delay Bandwidth
Queuing Delay
Packet loss, routers cycle out and drop packets when they need to force memory
Arthur C. Clarke
Predicted the internet
Cloud Networking Product - Optimize
Product to make things faster, costs more money
Bandwidth vs Throuput
Promise vs Actuality
Width of a bit
Propagation Speed / R Distance unnecessary
Satellite
Regenerate signal w/repeaters - Geostationary Satellites (less delay, faster) - Closer Satellites (more delay, slower)
Spatial coding
Sends only two values, color and repetitions
Twisted-Pair Copper Wire
Shielded, unshielded Varying speeds
Broadcast
Single sender to all receivers
Packet Sniffer
Software or hardware used to collect data travelling over a network
Access Network: Home Network
WiFI, Wireless Access Point Router, Firewall, NAT Cable or DSL Modem
HTTP2
increased flexibility at server level in sending objects sends most difficult objects first On>1
TCP - Transmission Control Protocol
provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
Choose the BEST answer: TCP views data as an unstructured, ordered stream of bytes. It tracks the order using the sequence number in a ______ as the byte-stream number of the _______ byte.
segment, first
You are a data packet. The router has determined that you will be transmitted out of its outgoing link 1. The _____ delay of all packets in front of you is your _______ delay.
transmission, queuing
Choose TWO best answers: Which entities among those listed (clearly and generally) benefit from cookies the most? The owners of the site the user is browsing on The user who is browsing The owners of the item listings The owners of the ad network
The owners of the item listings The owners of the ad network
Bottleneck link
Throughput decreases due to a smaller bandwidth connection
Fast and secure individual connection across Cloud Infrastructure
Traffic served from edge caches
Delays
Transmission Nodal processing Queueing Propagation
Wireless Transmission Measurement
Transmission Rate R (bps) and throughput
Improvements of DASH
User interactivity Host capability Internet traffic conditions
Communication links
Utilizing bandwidth Fiber, copper, radio, satellite
Cloud Networking Product - Connect
Virtual environment for customers to connect to other customers and the service
Internet founders
Vinton G. Cerf & Robert Kahn - worked to create internet concept and architecture Kleinrock - founder ARPAnet and expanded Baran - packet switching in military nets Gary Thuerk - spam email Kevin Mackenzie & Scott Fahlman - emogy Tim Berners-Lee - made WWW Ward Cunningham - repeat
Guided vs. Unguided Physical Media
Visible and invisible
Fiber Optics
Light projecting core Fastest
Root Servers
13 main DNS servers
How many bits are in 1 byte
8
Multiplexing
A form of transmission that allows multiple signals to travel simultaneously over one medium
Transmission between packet switch and analog networks require
A gateway for translation
Cloud Networking Product - Scale
A way to manage the traffic and stress of systems
Authentication is used to: A. Validate the user's right to access the system and information B. Transition from being digital-optional to being digital-centric C. Protect against brute force attacks where hackers use all combination of string to guess passwords or encryption keys D. Strike the right balance between security and smoothness throughout the entire user journey
A. Validate the user's right to access the system and information and C. Protect against brute force attacks where hackers use all combination of string to guess passwords or encryption keys
Network Stack
Application (Message) Transport (Segment) Network (Datagram) Link (Frame) Physical (Pulse/Wave)
Dr. Kleinrock
Created packet switching theory Founder of computer networking technology
Lines of Defense
Authentication Confidentiality Integrity Checks Access Restrictions Firewalls
What is the approximate average throughput in a path from source to destination? A. Transmission rate of the outgoing link closest to the source B. Transmission rate of the bottle neck link of the edge router closest to the source C. Transmission rate of the bottle neck link D. Throughput rate of the bottle neck link
C. Transmission rate of the bottle neck link
Networks
Collection of devices, routers, links Managed by an organization
Choose the best answer: ____ are often used in areas without access to DSL or cable-based Internet access. Communication satellite links Coaxial Cables Guided communication links Packet switching links
Communication satellite links
Cloud Networking Product Features
Connect Scale Secure Optimize
Content Provider Networks (CDN)
Enhanced security, added features, cost efficiency, access to data
Packet Switches
Forward packets (chunks of data) Routers and switches
Coaxial Cable
Intertwined twisted pairs Very fast
Transmission Delay
L/R Time it takes to push a packet into the link
Peering Link
Mutual connection between similarly sized ISPs
HTTP2 Disadvantage
No security over vanilla TCP connection Recovery from packet loss stalls all object transmissions Browsers have incentive to use pipelining
ISP Interconnections
Points of Presences (Large ISP opens door for smaller ISPs) Multi-homing (Multiple connections) Peering (Cost efficient, direct or via IXPs)
TCP offers:
Reliable data transfer Throughput Flow control Congestion control Timing
UDP offers:
Reliable data transfer Throughput No flow control, send data as fast as possible
Processing delay
The time required to examine the packet's header and determine where to direct the packet
How to define a region
The traffic within a geographical location where transmission is within 1 microsecond
Data Centers are not easily accessible because...
They are highly secure and remote
TTL
Time-To-Leave
Do we use DASH for streaming and video
We use TCP
Multihoming
When a Regional ISP connects to two larger ISPs Promotes security and decreases risk
N chooses k: ( N ) ( k )
n! / (k! (n-k)!)
Choose ALL that apply: What shouldn't be expected from application-layer protocols to regulate? _____ of a data packet the content the semantics the owner (i.e. host) the structure
the content and the owner
