Week Nine: 1. List 2 reasons why QoS is needed for VoIP. • Method of measuring level of service to end user. • Method of assessing assurancethat a particular application can meet its service requirements. 2. List 5 technical components of QoS • Availability • Throughput • Connection Setup Time • % of successful transmissions • Speed of fault detection and correction 3. List 4 ways in which QoS could be measured in an IP network. • Bandwidth • Packet Loss • Delay • Jitter 4. Define a ‘level’ of QoS. For a given session, the network must provide assurance that the measurement of the QoS parameters will fall within certain bounds. 5. What assumptions are made if UDP is used to transport data? Use of UDP assumes that network is not congested, and packet loss is relatively low. 6. List 2 effects of excessive data loss in a VoIP implementation. • Some CODECS can compensate for a small amount of data loss. • Excess data loss causes ‘drop-outs’, and lowers users perceptions of QoS. 7. List 5 ‘non-network’ QoS expectations. • Rapid service provisioning • Excellent Customer Service • Accurate Billing • Competitive Rates • Superior Marketing 8. Briefly describe 3 network approaches to solving QoS. • Ensure all required resources are dedicated prior to the session. • Fairly share resources depending on priority. • Overprovision the network . 9. What 2 levels of service does RSVP offer? • Guaranteed • Controlled Load 10. Explain the RSVP terms “Guaranteed” and “Controlled Load” Guaranteed - Close to Circuit Switching level of service. Controlled Load - Equivalent to best-effort under no-load. 11. Explain briefly how RSVP works RSVP is a signaling protocol that, in the context of Intserv, is used for admission control and resource reservation. There are two main control messages in RSVP:
• Path message – this message is sent by the sender to the receiver and is used to (1) carry the sender’s traffic specifications, and (2) set up the path. Upon receiving this message each node stores the previous node along the path. • Resv message – this message is sent by the receiver to sender and is used to perform admission control and resource reservation. Upon receiving such a message a node checks whether it has enough resources to satisfy the receiver requirements. If yes, it reserves resources; if not, it marks the message to indicate that the reservation is denied. In both cases the node forwards the message to the previous node (set up by the Path message) towards the source. 12. TOS bits that are set to 1 basically help speed up the packet flow. 13.
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