CS 6250 Quiz 12 (All Quizzes) 2026/2027 Latest Update |
Verified Questions and Correct Answers | Complete Study
Guide – Georgia Institute of Technology
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2026/2027 | GRADED A+ | 100 out of 100
Question:
When streaming stored multimedia applications, the user must download first the entire content before it can start
playing. (T/F)
Answer
False
Question:
With streaming stored multimedia applications, the user can pause, fast forward, skip ahead the audio/video. (T/F)
Answer
False
Question:
Which of the following applications is the least sensitive to network delays?
Streaming video
VoIP
Interactive games
File Transfer
Answer
File Transfer
Question:
Which of the following applications is the least tolerant to packet losses?
Streaming video
VoIP
Interactive games
File Transfer
Answer
File Transfer
Question:
What are the consequences of using TCP instead of UDP for VoIP applications? Select all that apply.
Less packet loss
More packet loss
Less end-to-end delay.
More end-to-end delay
Answer
Less packet loss
More end-to-end delay
Question:
Which of the following are QoS metrics for VoIP applications? Select all that apply.
End-to-end delay
Jitter
Packet loss
Available bandwidth
Answer
End-to-end delay
Jitter
Packet loss
Question:
In VoIP applications, increased packet jitter results in increased end-to-end delay. (T/F)
Answer
True
Question:
Which of the following has an impact on packet jitter?
Encoding delay
Decoding delay
The type of multimedia application
Network conditions such as buffer sizes, queueing delays, network congestion levels
Answer
Network conditions such as buffer sizes, queueing delays, network congestion levels
Question:
In VoIP applications, we have a harsher definition for packet loss, as we consider a packet to be lost if it never arrives
or if it arrives after its scheduled playout. (T/F)
Answer
True
Question:
With Forward Error Concealment we also transmit redundant data that can be used for reconstructing the stream at
the receiver's side. This approach to error recovery can lead to more bandwidth consumption. (T/F)
Answer
True
Question:
With interleaving we mix chunks of audio together so we avoid scenarios where consecutive chunks are lost. This
approach can lead to increased latency.
Answer
True
Question:
Which transport-level protocol is preferred for video content delivery?
Answer
TCP
Question:
What are the characteristics of good quality of experience from the user's perspective? Select that apply.
Low or zero re-buffering
High video quality
Low video quality variations
Low start up latency
Low or zero re-buffering
Answer
High video quality
Low video quality variations
Low start up latency
Question:
With throughout-based rate adaption, our goal is to have a buffer-filling rate that is greater than the buffer-depletion
rate.
Answer
True
Question:
With rate-based adaption, when the bandwidth changes rapidly, the player takes some time to converge to the right
estimate of the bandwidth, which can lead to overestimation of the future bandwidth. (T/F)
Answer
True
Question:
Having a single server for providing Internet content has the following disadvantages:
Single point of failure.
Bandwidth waste in high demand for the same content.
Scalability issues.
Potentially big geographic distance between Internet hosts/users and the server.
Answer
Bandwidth waste in high demand for the same content.
Scalability issues.
Potentially big geographic distance between Internet hosts/users and the server.
Question:
One of the advantages of using CDNs is that the routing protocols they use take important aspects into consideration,
such as congestion, latency, etc., in order to best deliver the content to the Internet users. (T/F)
Answer
False
Question:
There are several factors that can make a CDN network unreliable, such as misconfigured routers, power outages,
malicious attacks or natural disasters. (T/F)
Answer
True
As the Internet evolves, the topology of the ISPs has become flatter, and the number of IXPs increases as the time
progresses due to the services they offer and the lower costs for the ISPS. (T/F)
Answer
True
The major drawback of the "Enter Deep" approach is that, if one server is lost, that geographic area will experience a
higher delay and lower throughput. (T/F)
Answer
False
When using CDN servers for content delivery, there is more overhead than when using the traditional approach. (T/F)
Answer
True
For a CDN to deliver content to an Internet user, a cluster is mapped to a client first and then a server within that
cluster is selected. (T/F)
Answer
True
Picking the geographically closest cluster location for a user is always the best choice in terms of performance for
content delivery. (T/F)
Answer
False
By using consistent hashing for server selection, in the case of a server failure, the objects that the server was
responsible for can be taken care of by a random server within the same ID space. (T/F)
Answer
False
When using DNS caching, what would happen if a host A makes a request for a domain that was just previously
queried by another host?
Answer
The local DNS server will send the request to the appropriate DNS server to fetch the IP address.
The local DNS server will immediately answer the host with the IP address.
The request will be forward to the root servers first.
None of the above.
The local DNS server will immediately answer the host with the IP address.
What is the type of the following resource record: (amazon.com, dns.amazon.com, ?, TTL)?
A
NS
CNAME
MX
NS
IP Anycast assigns the same IP address to multiple servers in order to deliver content from CDNs by using the closest
server to a client based on BGP path length. (T/F)
True
HTTP redirection can only be used in order to share the load of content requests among servers. (T/F)
False
Having a single server for providing Internet content has the following disadvantages: SELECT ALL THAT APPLY
Single point of failure
Bandwidth waste in high demand for the same content
Scalability issues
Potentially big geographic distance between Internet hosts/users and the server
Single point of failure
Bandwidth waste in high demand for the same content
Scalability issues
Potentially big geographic distance between Internet hosts/users and the server
There are several factors that can make a CDN network unreliable, such as misconfigured routers, power outages,
malicious attacks or natural disasters.
True
False
True
The network topology of ISPs has become flatter over time, and the number of Internet Exchange Points (IXPs) has
increased.
True
False
True
The major drawback of the "Enter Deep" approach is that if one server is lost, that geographic area will experience a
higher delay and lower throughput.
True
False
False
When using CDN servers for content delivery, there is more overhead than when using the traditional approach.
True
False
True
For a CDN to deliver content to an Internet user, a cluster is mapped to a client first and then a server within that
cluster is selected.
True
False
True
Picking the geographically closest cluster location for a user is always the best choice in terms of performance for
content delivery.
True
False
False
When utilizing consistent hashing for server selection, in the event of a server failure, the responsibility for managing
the objects originally handled by the failed server is transferred to a randomly chosen server within the same ID space.
True
False
False
When using DNS caching, what would happen if a host A makes a request for a domain that was just previously
queried by another host?
The local DNS server will send the request to the appropriate DNS server to fetch the IP address.
The local DNS server will immediately answer the host with the IP address.
The request will be forward to the root servers first.
None of the above.
The local DNS server will immediately answer the host with the IP address.
What is the purpose of an NS record in DNS?
To translate domain names in IP addresses
To specify the mail server responsible for accepting email messages on behalf of the domain
To redirect one domain to another domain
To denote the authoritative name server for a domain
To denote the authoritative name server for a domain
IP Anycast assigns the same IP address to multiple servers in order to deliver content from CDNs by using the closest
server to a client based on BGP path length.
True
False
True
HTTP redirection can only be used in order to share the load of content requests among servers.
True
False
False
3 drawbacks to the traditional approach of providing content on the internet
1. Users are located everywhere
2. Can be popular resulting in a spike in demand and requests for same thing
3. Can be single point of failure
Content distribution network
Networks of multiple, geographically distributed servers and/or data centers, with copies of content (videos, but also
many other types of Web content), that direct users to a server or server cluster that can best serve the user's request.
Internet application challenges
1. Peering point congestion
2. Inefficient routing protocols
3. Unreliable networks.
4. Inefficient communication protocols.
5. Scalability
6. Application limitations and slow rate of change adoption.
2 major shifts that have changed the evolution of internet ecosystems
1. Large scale content delivery demand
2. Topological flattening
CDN server placement approaches
Deploying lots of small clusters to get as close as possible to the users, or deploying fewer but larger clusters to critical
areas
CDN server selection steps
Cluster selection and server selection
Limitations to choosing the closest geographically located cluster
1. Users may use remote LDNS
2. May not be the best choice in terms of actual end-to-end network performance. This can happen because of multiple
reasons.
What metric should be used for cluster selection?
Network-layer metrics such as delay, available bandwidth or both. Also, application-layer metrics.
Active measurements
LDNS could probe multiple clusters, such as by sending a ping request to multiple clusters for monitoring the RTT and
then use the "closest" server.
Passive measurements
The name server system in the CDN could keep a track of the performance metrics based on the current traffic
conditions.
What is the distributed 2 layer system?
1. coarse-grained global layer operates at larger time scale. This layer has a global view of client quality measurements.
It builds a data-driven prediction model of video quality.
2. A fine-grained per-client decision layer that operates at the millisecond timescale. It makes actual decisions upon a
client request. This is based on the latest (but possibly stale) pre-computed global model and up-to-date per-client
state.
Consistent hashing
Balances load by assigning roughly the same number of content IDs, and requires relatively little movement of these
content IDs when nodes join and leave the system. Servers and the content objects are mapped to the same ID space.
3 network protocols for server selection
DNS
HTTP redirection
IP Anycast
Why do we need DNS?
The identifiers we have for an Internet host is the IP address and the hostname. The advantage of using hostnames is
that they can be easily remembered by humans. The main disadvantage of hostnames is that they are consisting of
variable characters and thus it's difficult for routers to process them. Using this system can help us translate
hostnames to IP addresses.
How does DNS work?
1. It provides a distributed database implemented over a hierarchy of servers.
2. It is an application layer protocol that allows hosts to query this database and provide the translation of hostnames
to IP addresses.
Main steps that a host takes to use DNS
1. The user host runs the client side of the DNS application
2. The browser extracts the hostname www.someschool.edu (Links to an external site.) and passes it to client side of
the DNS application.
3. DNS Client sends a query containing the hostname of DNS
4. DNS Client eventually receives a reply which included IP address for the hostname
5. As soon as the host receives the IP addresses, it can initiate a TCP connection to the HTTP server located at that port
at that IP
What are some other services offered by DNS?
Mail server/host aliasing and load distribution
Why would a centralized model for DNS be bad?
1. It introduces a single point of failure.
2. It would be very difficult for a single server to handle all the volume of the querying traffic.
3. This model is based on a centralized database which cannot be close to all querying clients. This model would cause
significant delays and slow performance for the clients which are geographically distant
4. Maintaining this centralized database would be a big problem as we would have to update a huge database with
updates for every single host in the Internet.
DNS hierarchy consists of the following servers
Root DNS servers
Top level domain (TLD) Servers
Authoritative servers
Local DNS servers
DNS caching
Caches the responses. This helps reduce performance delay and make it more efficient.
After a server receives the DNS reply of mapping from any host to IP address, it stores this information in the Cache
memory before sending it to the client.
DNS Records
Mappings between hostnames and IP addresses. They are contained in the DNS reply messages
4 DNS Record fields
Name, value, Type, and TTL
Most common type of DNS Record
TYPE=A
TYPE=NS
TYPE=CNAME
TYPE=MX: the name is the alias hostname of a mail server, and the Value is the canonical name of the email server.
(abc.com, mail.dnsserver.abc.com, MX)
Type A DNS Record
The name is a domain name and value is the IP address of the hostname.
Type NS DNS Record
The name is the domain name, and the value is the appropriate authoritative DNS server that can obtain the IP
addresses for hosts in that domain.
Type CName DNS Record
The name is the alias hostname, and the value is the canonical name
Type MX DNS Record
The name is the alias hostname of a mail server, and the Value is the canonical name of the email server.
IP Anycast
Route a client to the "closest" server, as determined by BGP (Border Gateway Protocol), a routing protocol used for
inter-AS routing. This is achieved by assigning the same IP address to multiple servers belonging to different clusters.
Now, each of these servers will use the standard BGP to advertise this IP address. Thus multiple BGP routes for the
same IP address corresponding to different cluster locations will propagate in the public Internet.
HTTP Redirection Protocol
Essentially, when a client sends a GET request to a server, say A, it can redirect the client to another server, say B, by
sending an HTTP response with a code 3xx and the name of the new server.
Enter deep
CDNs place many smaller server clusters "deep" into the access networks around the world. The goal is to make the
distance between a user and the closest server cluster as small as possible, which reduces the delay and increases the
available throughput for each user. However, the downside to this highly distributed approach is that it is much more
difficult to manage and maintain so many clusters.
Bring home
CDNs place fewer larger server clusters at key points (typically in IXPs, not in access networks). There's not as many
server clusters to manage or maintain, so those tasks are easier, but the downside is that the users will experience
higher delay and lower throughput.
What role does DNS play in CDNs?
Notice the interplay of the DNS request/responses, and what the user's perspective of the whole exchange is. By
intercepting the requests with DNS, CDNs have the opportunity to choose where to direct users, based on location
and/or current conditions.
How are the metrics for cluster selection obtained?
Active and passive measurements
Why does DNS use a hierarchical scheme?
To solve the scalability problem
Iterative query process DNS
The querying host is referred to a different DNS server in the chain, until it can fully resolve the request.
Recursive query process DNS
The querying host, and each DNS server in the chain queries the next server and delegates the query to it.
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