Broadband Multimedia Network Report

1. With the appropriate use of diagrams and clear descriptive text: • Explain why an MPEG-DASH server will contain copies of a movie encoded at different quality levels and segmented into chunks • Explain how the MPD is used by a MPEG-DASH client to adapt its behaviour when retrieving content for playback, and clearly describe the differences between chunks made up of separate files and chunks represented as byte ranges • Explain the difference between a chunk's representation rate and the rate at which a chunk is retrieved • Explain the role of a playout buffer inside an MPEG-DASH client and when they are prefilled 2. Imagine you have a server containing a movie segmented into chunks and encoded at constant bitrates of 200, 500 and 1000 Kbps. With the appropriate use of diagrams and clear descriptive text: • How many bytes make up the chunks representing both 2 seconds and 8 seconds of content at the 200, 500 and 1000 Kbps representation rates? (Six different types of chunks in total.) • How many seconds would each of these chunks take to send if they were encapsulated in UDP/IP frames and transmitted at precisely 1600Kbps (at the IP layer), with no other overheads and no packet losses? 3. Imagine you have a standard web server containing a movie segmented into chunks and encoded at constant bitrates of 200, 500 and 1000 Kbps. Assume an additional 320 bytes of HTTP response overhead is required to encapsulate and send each chunk in response to GET requests from a DASH client. A single DASH client is connected to this server over a path exhibiting 35ms RTT and offering 1600Kbps in each direction at the IP layer. With the appropriate use of diagrams and clear descriptive text: • What is the path's BDP? • Assume the TCP layer's MSS is 1460 bytes, how long would it take for the DASH server's TCP layer cwnd to reach and exceed BDP during Slow Start from an initial window (IW) of 10 MSS? • If the TCP stack at the DASH server begins in Slow Start with IW=10 MSS for the transmission of every chunk, how long does it take to transmit HTTP-encapsulated 4-second chunks encoded at the three representation rates? (Assume no packet losses or packet reordering along the path.) 4. With the appropriate use of diagrams and clear descriptive text: • Explain briefly what is meant by tail-drop FIFO queuing. • Explain what is meant by BufferBloat, and what are the consequences for a VoIP flow's latency and throughput when a VoIP flow and bulk TCP flow share and congest a FIFO bottleneck queue. • Explain the role and operation of the active queue management (AQM) schemes known as PIE and FQ-CoDel. For both PIE and FQ-CoDel separately, explain how they impact on latency and bandwidth experienced by individual flows when multiple flows compete at a bottleneck router. 5. With the appropriate use of diagrams and clear descriptive text: • Consider a home router that is forwarding packets out of the house over a link that carries 12Mbit/sec downstream and 1Mbit/sec upstream at the IP layer. How many two-way RTP-based VoIP calls, using standard G.711a codecs, could be active at the same time between the house and outside world? (Assume standard VoIP encapsulation) 6. NBN Co currently offers two analog voice ports (called UNI-V) on its Customer Premised Equipment (CPE) for fibre based services. • What signaling protocol does the UNI-V use between CPE and access provider? • What codec does the UNI-V use? • What is the packetisation rate for the codec? • What method(s) does NBN Co use to ensure QoS for UNI-V traffic traversing its network? • What levels of QoS are there?