CS6250 Computer Networks Exam 1
Questions and Answers (Verified
Answers) ||ACTUAL EXAM 2026/2027
TEST!! Graded A+
What are advantages and disadvantages of a layered
architecture? - ✔✔✔ ANSWER-Each protocol layer
offers different services.
Layered Architecture - ✔✔✔ ANSWER-Each protocol
layer offers different services.
Layered Architecture Advantages - ✔✔✔ ANSWER--
Scalability,
- Flexibility
- Ease of adding / removing components making it
easier for cost-effective implementations.
Layered Architecture Disadvantages - ✔✔✔ ANSWER--
Some layers functionality depends on the information
from the other layer and violates the goal of layer
separation;
- One layer may duplicate lower layer functionalities
- Overhead both in computation
,- Overhead in message headers caused by abstraction
barriers between layers.
OSI and Five-Layered Internet model Similarities -
✔✔✔ ANSWER-Many of the layers are the same
OSI and Five-Layered Internet model Differences -
✔✔✔ ANSWER-- Three of the layers are combined in
the 5-layered model.
- Specifically the five-layer model combines the
- Application
- Presentation
- Session layers
from the OSI model into a single Application layer.
What are sockets? - ✔✔✔ ANSWER-- A network socket
is a software structure within a network node of a
computer network that serves as an endpoint for
sending and receiving data across the network.
- The structure and properties of a socket are defined
by an application programming interface (API) for the
networking architecture.
- Sockets are created only during the lifetime of a
process of an application running in the node.
- ."A process sends messages into, and receives
,messages from, the network through a software
interface called a socket.
- Let's consider an analogy to help us understand
processes and sockets. A process is analogous to a
house and its socket is analogous to its door....a
socket is the interface between the application layer
and the transport layer within a host." - Kurose and
Ross, 2.1
Packet Classification - ✔✔✔ ANSWER-As the Internet
becomes increasingly complex, networks require
quality-of-service and security guarantees for their
traffic.
Packet forwarding based on the longest prefix
matching of destination IP addresses is insufficient.
We need to handle packets based on multiple criteria
such as TCP flags, source addresses, and so on.
3 Established Variants of Packet Classification - ✔✔✔
ANSWER-1. Firewalls: Routers implement firewalls at
the entry and exit points of the network to filter out
unwanted traffic or to enforce other security policies.
2. Resource reservation protocols: For example,
, DiffServ has been used to reserve bandwidth between
a source and a destination.
3. Routing based on traffic type: Routing based on the
specific type of traffic helps avoid delays for time-
sensitive applications.
Simple Solutions to Packet Classification Problem -
✔✔✔ ANSWER-Linear Search:
Firewall implementations perform a linear search of
the rules database and keep track of the best-match
rule.
This solution can be reasonable for a few rules, but
the time to search through a large database that may
have thousands of rules can be prohibitive.
Caching:
Another approach is to cache the results so that
future searches can run faster. This has two problems:
The cache-hit rate can be high (80-90%), but still, we
will need to perform searches for missed hits.
Even with a high 90% hit rate cache, a slow linear
Questions and Answers (Verified
Answers) ||ACTUAL EXAM 2026/2027
TEST!! Graded A+
What are advantages and disadvantages of a layered
architecture? - ✔✔✔ ANSWER-Each protocol layer
offers different services.
Layered Architecture - ✔✔✔ ANSWER-Each protocol
layer offers different services.
Layered Architecture Advantages - ✔✔✔ ANSWER--
Scalability,
- Flexibility
- Ease of adding / removing components making it
easier for cost-effective implementations.
Layered Architecture Disadvantages - ✔✔✔ ANSWER--
Some layers functionality depends on the information
from the other layer and violates the goal of layer
separation;
- One layer may duplicate lower layer functionalities
- Overhead both in computation
,- Overhead in message headers caused by abstraction
barriers between layers.
OSI and Five-Layered Internet model Similarities -
✔✔✔ ANSWER-Many of the layers are the same
OSI and Five-Layered Internet model Differences -
✔✔✔ ANSWER-- Three of the layers are combined in
the 5-layered model.
- Specifically the five-layer model combines the
- Application
- Presentation
- Session layers
from the OSI model into a single Application layer.
What are sockets? - ✔✔✔ ANSWER-- A network socket
is a software structure within a network node of a
computer network that serves as an endpoint for
sending and receiving data across the network.
- The structure and properties of a socket are defined
by an application programming interface (API) for the
networking architecture.
- Sockets are created only during the lifetime of a
process of an application running in the node.
- ."A process sends messages into, and receives
,messages from, the network through a software
interface called a socket.
- Let's consider an analogy to help us understand
processes and sockets. A process is analogous to a
house and its socket is analogous to its door....a
socket is the interface between the application layer
and the transport layer within a host." - Kurose and
Ross, 2.1
Packet Classification - ✔✔✔ ANSWER-As the Internet
becomes increasingly complex, networks require
quality-of-service and security guarantees for their
traffic.
Packet forwarding based on the longest prefix
matching of destination IP addresses is insufficient.
We need to handle packets based on multiple criteria
such as TCP flags, source addresses, and so on.
3 Established Variants of Packet Classification - ✔✔✔
ANSWER-1. Firewalls: Routers implement firewalls at
the entry and exit points of the network to filter out
unwanted traffic or to enforce other security policies.
2. Resource reservation protocols: For example,
, DiffServ has been used to reserve bandwidth between
a source and a destination.
3. Routing based on traffic type: Routing based on the
specific type of traffic helps avoid delays for time-
sensitive applications.
Simple Solutions to Packet Classification Problem -
✔✔✔ ANSWER-Linear Search:
Firewall implementations perform a linear search of
the rules database and keep track of the best-match
rule.
This solution can be reasonable for a few rules, but
the time to search through a large database that may
have thousands of rules can be prohibitive.
Caching:
Another approach is to cache the results so that
future searches can run faster. This has two problems:
The cache-hit rate can be high (80-90%), but still, we
will need to perform searches for missed hits.
Even with a high 90% hit rate cache, a slow linear
