Networking Functions

What does CDN stand for?

Content Delivery Network.

What is the main purpose of a CDN?

To cache and deliver content from geographically distributed servers closer to end users.

Why does a CDN improve performance?

Users retrieve data from a nearby CDN server instead of a distant central server.

What problem does a CDN primarily reduce?

Latency caused by geographic distance.

What does VPN stand for?

Virtual Private Network.

What is the primary purpose of a VPN?

To securely connect a user or network to a remote private network.

How does a VPN protect data?

It encrypts data while it travels across an untrusted network such as the public internet.

What is a VPN concentrator?

A central device that handles VPN connections and performs high-speed encryption and decryption.

Where can VPN concentrator functionality be integrated?

Inside a next-generation firewall.

Why might a large organization use a purpose-built VPN concentrator?

It can provide high throughput and support hundreds or thousands of simultaneous users.

Can a VPN concentrator run as software?

Yes. Smaller networks may run one as software on an existing operating system.

What does QoS stand for?

Quality of Service.

What is the purpose of QoS?

To assign different priorities to network applications and traffic.

What other terms can describe QoS?

Traffic shaping or packet shaping.

Which traffic normally receives higher QoS priority?

Delay-sensitive traffic such as VoIP, live audio, and video conferencing.

Which traffic normally receives lower QoS priority?

File transfers, downloads, and backups that can tolerate delays.

Where can QoS be configured?

On devices such as firewalls, routers, and switches.

A video call becomes choppy during a large file upload. What should be configured?

QoS should prioritize the video-call traffic over the file transfer.

What does TTL stand for?

Time to Live.

What is the purpose of TTL?

To stop a task, packet, or cached entry from remaining active indefinitely.

What does TTL measure in an IP packet?

The number of router hops the packet is allowed to make.

What happens to an IP packet’s TTL at every router?

The router decreases it by one.

What happens when an IP packet’s TTL reaches zero?

The router discards the packet.

How does TTL help prevent routing loops?

A looping packet eventually reaches a TTL of zero and is removed from the network.

What is a routing loop?

A condition in which routers repeatedly forward a packet back and forth without reaching its destination.

What can cause a routing loop?

An incorrect routing configuration, such as a mistaken IP address in a static route.

How might a routing loop appear in traceroute?

The same router addresses repeat in an alternating pattern.

What is the typical default TTL for Windows mentioned in the transcript?

128 hops.

What is the typical default TTL for macOS and Linux mentioned in the transcript?

64 hops.

A Windows packet crosses 20 routers. What TTL remains if it began at 128?

108.

What does TTL represent in DNS?

The number of seconds a DNS record should remain cached.

What happens when a DNS TTL expires?

The cached record is removed, and another DNS query is needed.

How long is a DNS TTL of 300?

300 seconds, or five minutes.

Why might users briefly continue reaching an old server after its IP address changes?

Their cached DNS record has not yet reached its TTL expiration.

What commands can be used to perform DNS lookups?

nslookup and dig.

What is the key difference between IP TTL and DNS TTL?

IP TTL counts router hops, while DNS TTL measures cache duration in seconds.