Week 11 - VoIP, IRC & BotNets (35-L38)

Question 1

What are the main parts of a VoIP network; Explain different parts

Answer 1

IP network: LAN

IP PBX: SW / Appliance that controls call but does not handle it;

Softphones / Headsets: End user device

VoIP Gateway: Bridge between standard phone network and VoIP

Question 2

Explain the key VoIP technologies and their differences?

Answer 2

SIP/RTP:

Zfone: not based on PKI, implements security in another way;

Skype: Implements various security algorythms for voice encryption, key exchange, verification, call setup creation.;

Asterisk: mainly used in companies.

Question 3

What transport protocols are available and what is the difference?

Answer 3

RTP: standard protocol;

SRTP: uses AES to encrypt voice data

Question 4

What are tie lines?

Answer 4

Connections between two PBX in remote locations

Question 5

What are channel modes?

Answer 5

Preferences that can be set per channel. E.g. Max number of users, secret passwords, private mode, invite only, etc

Question 6

What is DCC?

Answer 6

Direct Client to Client messages. Clients uses IRC server to establish connection, but then do communication directly.

Question 7

What is the difference between Circuit and Packet networks?

Answer 7

Packet networks are used for normal data packets, where packets are split and send over the network on different routes. Circuit is used in VoIP, where circuit between A and B is established first.

Question 8

What signaling protocols are available and what is the difference?

Answer 8

H.323: more complex, more features; Binary;

SIP: easier to implement. More like http protocol; Textual

Question 9

What are the QoS issues of VoIP?

Answer 9

• Packet loss
• Bandwith
• Delay
• Jitter
• Echeo
• Security
• Reliability

Question 10

What is an IRC botnet and how does it work? And what are they used for?

Answer 10

Bots (compromised computers) connect to IRC server to dedicated IRC channel and perform different tasks: Automatic replies; Monitoring / protocoling; Stay as a channel operator; Provide games; Creating stats; Wait for commands from C&C server

Question 11

What is IRC?

Answer 11

Internet Relay Chat, Application layer protocol that allows the exchange of messages in form of text. Can happen with a IRC server or without (direct messages)