HTTP
What is the difference between a persistent connection in HTTP/1.1 and a pipelined connection?
Persistent keeps the TCP connection open for multiple requests; pipelining allows sending multiple requests without waiting for responses, but still suffers from HOL blocking.
What is the purpose of the DHCP protocol?
To dynamically assign IP addresses to clients.
How many layers are in the OSI model?
7
A single device failure won’t disrupt communication in this topology, because each device is connected to at least two others. However, it requires careful planning for cable layout.
What is a Mesh topology?
What does DNS stand for?
Domain Name System
In HTTP/2, what mechanism is used to mitigate Head-of-Line (HOL) blocking present in HTTP/1.1?
Multiplexing and frame interleaving over a single TCP connection.
Why does DHCP use broadcast messages during the discovery phase?
Because the client has no IP address yet and does not know the server’s address.
Which OSI layer is responsible for segmenting application data and ensuring correct order at the receiver?
Transport layer.
In a physical topology where every device is directly connected to all others, which topology is used?
Mesh
Which type of DNS query asks the DNS server to resolve a name on behalf of the client?
Recursive query
In HTTP/1.1, how many TCP connections are required to download a page with 5 objects?
6 (1 for the HTML + 5 for the objects).
Explain the difference between DHCP Discover and DHCP Request messages.
Discover → client searches for available servers; Request → client asks for a specific offer from one server.
Explain the difference between the Transport layer and the Network layer in OSI.
Network layer: routing, addressing, end-to-end packet delivery.
Transport layer: reliability, flow control, segmentation, process-to-process delivery.
This device makes forwarding decisions based on destination IP addresses and maintains tables that are dynamically updated by protocols such as RIP or OSPF.
What is a router?
In DNS, what is the role of a root server?
Direct queries to the appropriate TLD server
In HTTP caching, what is the difference between Cache-Control: no-cache and Cache-Control: no-store?
no-cache: resource must be revalidated with the origin server before use;
no-store: resource cannot be stored at all (not cached).
A network has two DHCP servers configured with the same pool of addresses. What is the risk, and what is the correct way to implement redundancy?
Risk: two clients may receive the same IP. Correct solution: split the address pool or use failover with non-overlapping ranges.
Why is the Transport layer considered “end-to-end” while the Network layer is considered “hop-to-hop”, and how do these two types of reliability complement each other?
Network layer (L3):
Ensures datagram delivery from source host to destination host.
Routing decisions and forwarding are made hop-to-hop by routers.
Reliability is limited — IP is best-effort, may drop, duplicate, or reorder packets.
Transport layer (L4):
Ensures delivery from source process to destination process (end-to-end).
Provides sequencing, acknowledgments, retransmissions, and flow control.
Corrects errors and losses that the Network layer does not handle.
A type of network where central server is not used.
What is a peer to peer network
What is the main advantage of iterative DNS queries?
Reduces server load by letting the client follow referrals
Why did HTTP/3 migrate from TCP to UDP, and what protocol was introduced to handle reliability and congestion?
To avoid TCP head-of-line blocking and enable faster recovery; HTTP/3 uses QUIC (on top of UDP).
At 87.5% of the lease time, what happens if the server does not respond?
The client broadcasts to any available DHCP server. If no ACK is received, the lease expires and the client must stop using the IP.
Map the following protocols to their OSI layers: HTTP, IP, ARP, Ethernet, DNS, TCP.
HTTP → Application
DNS → Application
TCP → Transport
IP → Network
ARP → Data Link
Ethernet → Data Link
Devices communicate directly without a central server. Links are one-way at a time, and signal delay depends on the medium. Identify topology and duplex mode.
Topology: Peer-to-peer
Duplex mode: Simplex or half-duplex
Which DNS server holds the original zone file for a domain?
Authoritative server