Chapter 1 Flashcards
What is a device that is hooked up to the internet called?
A host, an end system
What is the thing that data travels through to get to another system in the internet chain called (i.e. wires, optical fibers, radio spectrums, etc.)?
A communication link
What are packages of information (info + data) that are transmitted over the internet called (think about them like trucks moving cargo)
packets
What are the things called that act like roundabouts or post offices, receiving packets and then forwarding them on to another destination
packet switches
What are two types of packet switches?
Routers and link-layer switches
What are the ISPs called that have high-speeds and serve national and international connections?
Upper-tier ISPs
What are the ISPs called that are local, have slower speeds, and are connected to upper-tier ISPs?
lower-tier ISPs
What are the two most important internet protocols called?
TCP and IP
What does TCP stand for?
Transmission Control Protocol
What does IP stand for?
Internet Protocol
What group invents the standards for the internet?
The IETF (The Internet Engineering Task Force)
What are the IETF’s standards documents called?
RFCs (Requests for Comments)
What body sets standards for network components like network links, ethernet, and WiFi?
The IEEE (Institute of Electrical and Electronics Engineers)
What is a set of rules that the sending program must follow so that the Internet can deliver the data to the destination program called?
A socket interface
What is another word for a host?
An end system
What two categories can hosts be divided into?
clients and servers
Where on the network are hosts located?
The network edge
What are the buildings called where large groups of servers reside?
data centers
What is AWS?
Amazon Web Services (a cloud)
What are the hosts in data centers called?
blades
What are 3 things that blades typically have/are composed of?
CPU, memory, disk storage
What are blades stacked in?
Racks
What is a network that physically connects and end system to the first router called?
An access network
What is another term for a “first router”?
an edge router
What are the two most common types of broadband residential access today?
DSL and cable
What does DSL stand for?
digital subscriber line
What non-computing device also is used on DSL?
the telephone line
What takes digital data and translates it into high-frequency tones that are then transmitted over telephone wires?
a DSL modem
What translates the high-frequency signals sent from a DSL modem back into digital data?
DSLAM (digital subscriber line access multiplexer)
How can one phone line carry data over what looks like 3 separate links?
Dividing transferred data into 3 frequency categories:
- High Speed
- Medium Speed
- Low Speed
What does CO stand for?
Central Office
What is it called when upstream transfer rates (host to ISP) and downstream transfer rates (ISP to host) of data are different?
asymmetric
What 4 things limit the speed of a DSL service?
- Service Level you pay for
- Physical distance from home to CO (max 10 miles)
- Gauge of the line
- Electrical inteference
What does cable internet access share a line with?
cable TV
Cable typically uses a hybrid system. What two mediums does it typically use?
fiber optic cable and coaxial cable
What are the modems used for cable access called?
cable modems
What kind of port does a cable modem typically connect through?
an ethernet port
What are two big downsides to cable access?
traffic jams and collisions
What is an up-and-coming tech that has higher speeds than cable and DSL?
Fiber to the home (FTTH)
What does AON stand for?
Active Optical Network
What does PON stand for?
Passive Optical Network
What does ONT stand for?
Optical Network Terminator
What is an upside to 5G fixed wireless?
No cables required. Everything uses through beam-forming tech
What is another name for IEEE 802.11 technology?
WiFi
How are computer bits sent through physical mediums over the internet? In what two forms?
Electromagnetic waves or optical pulses
What are the two basic types of physical media?
- Guided media (cables)
2. Unguided media (waves in atmosphere)
What is the least expensive type of guided transmission medium?
Copper wire (twisted pair)
How fast can twisted pair copper wire get?
Up to 10 Gbps for distances of up to 100m
True or False: coaxial cable be used as a guided shared medium?
True
What is the preferred type of physical medium for long-haul guided transmission, particularly for overseas links?
fiber optics
What are fiber optics immune to?
electromagnetic interference
True or False: Fiber optic cables are easy to tap
False
Which can transfer bits at faster rates: copper wires or fiber optics?
fiber optics
What is the loss of strength in a radio signal as it travels over a distance and around/through obstructing objects called?
Path loss and shadow fading
What is the loss of radio signal strength due to signal reflection off of interfering objects called?
multipath fading
What are two types of satellites used in communications?
- Geostationary satellites
2. low-earth orbiting satellites (LEOs)
Which satellite type is closer to earth? Geostationary satellites or LEOs?
LEO
What is the name given to the mesh of packet switches and links that interconnects the internet’s end systems?
the network core
What are long messages broken into smaller chunks of data called?
packets
What types of system is it that requires the entire packet be received before it can begin to transmit the first bit of the packet onto the outbound link?
store-and-forward transmission
What happens when an incoming packet encounters a full queue at a store-and-forward based packet switch?
packet loss
What is the list of destination addresses a router uses to decide which outbound link to forward packets called?
a forwarding table
What are the two fundamental approaches to moving data through a network called?
- circuit switching
2. packet switching
Which system, circuit switching or packet switching, reserves resources needed to provide all the communication between end system?
circuit switching
When a frequency is divided for multiplexing, what is the resulting piece of frequency called?
bandwidth
What are two types of multiplexing?
- Frequency-division multiplexing (FDM)
2. time-division multiplexing (TDM)
What is one downside to circuit switching?
When lines aren’t being used, they are idle (silent periods), so essentially resources are being wasted/underutilized.
What is a downside of packet switching?
delays in queueing can make it hard to make phone calls or video calls
Which is cheaper: packet switching or circuit switching?
packet switching
Is the trend headed towards more packet switching or more circuit switching?
More packet switching.
What phrase describes the way in which ISPs connect to other ISPs so that any end user can connect with any other end user or content provider.
“a network of networks”
What does PoP stand for?
point(s) of presence
What does IXP stand for?
internet exchange point
What is a group of routers at the same location in a provider’s network that allow customer ISPs to connect into the provider ISP called?
PoP
What is multihoming?
connecting to more than one regional or tier-1 ISP (ensures service in the case of a provider failure)
How can ISPs cut costs?
By peering. They connect directly to each other and then don’t have to pay for internet traffic that would have been routed through a provider ISP
What is a meeting point where multiple ISPs can peer together called? It typically is a stand-alone building with its own switches.
An IXP
What is a term that describes that amount of data that can be transferred?
throughput
What types of delays make up total nodal delay?
- Nodal processing delay
- Queuing delay
- Transmission Delay
- Propagation Delay
Delay type caused by examining the packet’s header and determining where to direct the packet and check for bit-level errors.
Processing Delay
Delay type caused by waiting in line to be transmitted (other packets arrived ahead of you that need to be processed first)
Queuing Delay
Delay caused by the amount of time needed to push all of a packet’s bits into a link
Transmission Delay
Type of delay caused by the time required to move the physical distance from point a to b through a medium
Propagation Delay
Design your system so that the traffic intensity is no greater than ____
1
Where does total nodal delay take place?
At one router (and traveling to the next)
What is the delay called that encompasses the total delays accrued from the source to the final destination in a network?
End-to-End Delay
What is the rate (in bits per second) at which Host B is receiving a file?
instantaneous throughput
What are the five layers of the internet protocol stack?
- Application
- Transport
- Network
- Link
- Physical
What is a transport-layer packet called?
a segment
When it comes to TCP and UDP, which one gives congestion control and has transmission throttles?
TCP
What are network layer packets known as?
datagrams
What is the Network Layer also commonly called?
The IP layer
What are link layer packets also called?
frames
Do routers and link-layer switches implement all 5 layers of the protocol stack?
No (typically 2-3 layers)
Give the four terms used when a message goes through encapsulation from a host to destination
- application layer message
- transport layer segment
- network layer datagram
- link-layer frame
What is the group of data that is encapsulated by the next layer referred to as?
a payload field
What is the general term given to bad stuff that can enter and infect our devices?
Malware
What is a networks of hundreds or thousands of similarly compromised devices that distribute spam or DoS attacks called?
A botnet
What is a type of malware that can spread itself from one system to another called?
self-replicating
What are 3 types of DoS attacks?
- Vulnerability attacks
- Bandwidth flooding
- Connection flooding
If a DoS attack from a single system is detected it can be blocked. To get around this, many attacks are of what type?
DDoS (Distributed Denial of Service)
What is a passive receiver that records a copy of every packet that flies by called?
a packet sniffer
True of False: Only wireless connections are susceptible to sniffing?
False. Ethernet, cable, and broadcast packets are also vulnerable, as are routers and links.
What is one of the best defenses when it comes to sniffing?
Cryptography
What is injecting packets into the internet with a false source address called?
IP spoofing
What is a mechanism that allows us to determine with certainty that a message originates from where we think it does called?
end-point authentication
What is a reason the internet is so insecure?
Because its original design was for it to be used by mutually trusting users with no need for security.
