Chapter 1 Flashcards
What is telecommunication?
The electronic transmission of signals for communication between a sender and a receiver.
How does communication occur over a client-server model?
The client process (software) on the client’s machine makes a request to a server process (software) on a server machine which replies.
What is the Ethernet standard?
802.3
What is the bluetooth standard?
802.15
What is the wireless standard?
IEEE created a wireless LAN standard dubbed 802.11
What is a computer network?
A collection of autonomous computers interconnected by a single technology
Outline the issue of resource sharing.
Make all programs, equipment, and especially data available to anyone
on the network without regard to the physical location of the resource or the user
How does communication occur over a peer-to-peer model?
Every person can, in principle, communicate with one or more other people; there is no fixed division into clients and servers
What are five uses of networks?
- Access Information
- Ecommerce
- Entertainment
- Person to Person Communication
- Internet of Things
List 4 types of computer networks.
- Mobile and Broadband access networks
- Data Center Networks
- Transit Networks
- Enterprise Networks
What is Metcalfe’s Law?
Bob Metcalfe, the inventor of Ethernet, hypothesized that the value of a network is proportional to the square of the
number of users; thus, Internet popularity comes from its size.
What does GPS stand for?
Global Positioning System
What is NFC?
Near Field Communication allows mobile device to act as an RFID (Radio Frequency Identification) smart-card and interact with a nearby reader for payment
Describe what a CDN is as content provider network
Content Delivery Network is a large collection of servers, geographically distributed so content is close to the users requesting it
Describe the purpose of transit networks.
Traditionally called backbone networks, these networks carry traffic between the content provider and the ISP (Internet Service Provider) with service charges for both parties.
What are some characteristics of a enterprise network?
- Allows resource sharing for devices and information (sometimes uses VPN)
- Allows IP telephony or VoIP (Voice over IP)
- Allows desktop sharing
- Allows electronic business communication
What are two ways to classify networks?
- Transmission Technology
- Scale
What are the two types of transmission technology?
Broadcast links and point-to-point links
Briefly describe point-to-point links.
Point-to-point links connect individual pairs of machines. Packets may have to first visit one or more intermediate machines when going from source machine.
What is unicasting?
A point-to-point transmission with exactly one sender and exactly one receiver .
What is a broadcast network?
Communication channel shared by all the machines on the network; packets sent by any machine are received by all the others unless it contains an address field for an intended recipient. Here the machine processes it and ignores if its not the target.
What is broadcasting in a broadcast network?
When a packet with special code is transmitted, and it is received and processed by every machine on the network.
What is multicasting on a broadcast network?
Transmission to a subset of the machines
What wireless network is standardized as 802.16?
A MAN with wireless Internet access.
What are some variations of WAN?
WAN can be implemented with:
1. Leased lines
2. Internet Connectivity (VPN)
3. ISP network
What is a internetwork or internet?
A collection of interconnected networks
What is a common way to connect to the Internet from home?
A common method for connecting to the Internet from your home is to send signals over the cable television infrastructure.
What was ARPANET (Advanced Research Projects Agency Network)?
The first public packet-switched computer network. The software was split into two parts; subnet and host.
What was NSFNET( National Science foundation) ?
A backbone network designed to be a successor to the ARPANET that would be open to all university research groups, allowing them to communicate without having to contract with the Department of Defense
Describe the evolution of the Internet architecture.
Conventionally, the Internet architecture has been viewed as a hierarchy but over the past decade, the conventional hierarchy has evolved and ‘‘flattened’’ dramatically.
How are circuit and packet switching used?
Packet switching comes from the Internet community
Circuit switching comes from telephone companies
Outline the generations of mobile networks?
a) First Generation transmitted voice calls as continuously varying (analog) signals using AMPS (Advanced Mobile Phone System)
b) Second Generation transmitted voice calls in digital form to increase capacity, improve security, and offer text messaging using GSM (Global System for Mobile communications)
c) Third Generation (3G) offer digital voice and broadband digital data services
d) Fourth Generation 4G later known as LTE (Long Term Evolution) emerged with faster speeds
e) Fifth Generation promises faster speeds up to 10 Gbps
What are the two 802.11 network modes?
Ad hoc and access point/ infrastructure mode
The key idea for overcoming variable wireless conditions is ___.
path diversity
List the versions of 802.11 and network speed.
- Original 802.11 ran at either 1 Mbps or 2 Mbps
- 802.11b used spread spectrum for rates up to 11 Mbps
- 802.11a/g rates were boosted to 54 mbps using OFDM (Orthogonal Frequency Division Multiplexing) modulation
- 802.11ac can run at 3.5 Gbps
- 802.11ad can run at 7 Gbps (only indoors within a single room)
What handles transmission collision in 802.11 networks?
CSMA (Carrier Sense Multiple Access) scheme
Limitations of 802.11 networks when compared to mobile phone networks.
Of limited value compared to mobility in mobile phone networks
List all the 802.11 security schemes overtime.
- WEP (Wired Equivalent Privacy)
- WEP replaced by WiFi Protected Access (initially called WPA)
- WiFi Protected Access (WPA) replaced by WPA2 and 802.1X
Outline the design issue of reliability in networks?
- Make a network operate correctly even though it is comprised of a collection of components that are themselves unreliable
- Find a working path through a network using routing
Outline the design issue of resource allocation in networks?
- Scalable designs continue to work well when network gets large
- Statistical multiplexing: sharing based on the statistics of demand
Outline the design issue of evolvability in networks?
- Use protocol layering structuring mechanism to support change by dividing the overall problem and hiding implementation details
- Allowing for incremental deployment of protocol improvements over time
Outline the design issue of security in networks?
- Confidentiality mechanisms defend against eavesdropping on communications
- Authentication mechanisms prevent someone from impersonating someone else
- Integrity mechanisms prevent surreptitious changes to messages
Describe a network architecture.
A set of layers and protocols
Adding headers is called ___
Encapsulation
Removing headers on destination is called___
D encapsulation
List the six service primitives that provide a simple connection-oriented
service.
LISTEN Block waiting for an incoming connection
CONNECT Establish a connection with a waiting peer
ACCEPT Accept an incoming connection from a peer
RECEIVE Block waiting for an incoming message
SEND Send a message to the peer
DISCONNECT Terminate a connection
What are the seven layers of the OSI (Open Systems Interconnection) model?
Physical, data link, network, transport, session, presentation and application
Outline the role of the Physical layer in the OSI model.
This layer is responsible for transmitting raw bits over a physical medium, such as electrical, mechanical, and functional specifications to connect two systems. Example of protocol used: Ethernet
Outline the role of the Data Link layer in the OSI model.
Layer provides reliable transfer of information across the physical link through framing, error control and flow control. The data link layer packages data from the physical layer into groups called blocks, frames or packets and adds an header. E.g. Ethernet protocol using CSMA method
Outline the role of the Network layer in the OSI model.
The network layer establishes, maintains, and terminates connections. Example of protocol: IP
Outline the role of the Transport layer in the OSI model.
The transport layer controls and ensures the end-to-end integrity of the data message propagated through the network between two devices, providing the reliable, transparent transfer of data between two endpoints. Example of protocol: TCP paired with IP
Outline the role of the Session layer in the OSI model.
It defines how to start, control and end conversations (called sessions) between applications. Example of protocol: ZIP (Zone Information Protocol )
Outline the role of the Presentation layer in the OSI model.
It specifies how end-user applications should format the data thereby translating between different data formats and protocols. Example of protocol: HTTP/ HTML (agent)
Outline the role of the Application layer in the OSI model.
The applications layer provides distributed information services and controls the sequence of activities within an application and also the sequence of events between the computer application and the user of another application. Example of protocol: Hypertext Transfer Protocol (HTTP), RTP, SMTP, DNS
What are the four layers of the TCP/IP Reference Model?
Link, Internet, Transport, Application
What are the two network standard categories?
- De Facto - happened, without any formal plan
- De Jure - adopted through the rules of some formal standardization body
Who is PTT?
Post, Telegraph & Telephone administration is a branch of govenrment having telecommunication authority
Who is ITU?
International Telecommunication Union standardize international telecommunications
Who is ISO?
International Standards Organization publishes and produces international standards
Who is NIST?.
National Institute of Standards and Technology is part of the U.S. Department of Commerce
Who is IEEE?
Institute of Electrical and Electronics Engineers is the largest professional organization in the world.
Who is IAB?
Internet Activities Board creates RFC.
Who is W3C?
World Wide Web Consortium develops protocols and guidelines to facilitate long-term growth of the Web
