Resource Sharing or Designing Access Network For Low Cost.

Transcription

1 Resource Sharing or Designing Access Network For Low Cost

2 Traffic Percentile What Drives Demand for Bandwidth? Usage In North America, the median usage is 4 GB per month, while the mean is almost 5 GB. Top users consistently exceeded 5 TB of monthly usage. % 8% Monthly Percentile Byte Contribution % of heaviest upstream users account for 4% of upstream bytes. 6% Median monthly consumption on fixed access networks in Asia-Pacific is roughly GB, and a mean is more than 5 GB The average user of a fixed access network in North America is active online for almost 97 hours per month, in Asia Pacific hours/month. 4% % % % % 5% % % % 4% 5% 6% 7% 8% 9% % Subscriber Percentile North America (upstream) North America (downstream) Asia-Pacific (Upstream) Asia-Pacific (downstream) Source: Fall Global Internet Phenomena Report, Sandvine, Inc. (

3 What Drives Demand for Bandwidth? Applications 45.7: percent of downstream traffic on North American fixed access networks attributable to Real-Time Entertainment SD IPTV: -4 Mb/s HD IPTV: 8- Mb/s D HD IPTV: 5-5 Mb/s Source: Fall Global Internet Phenomena Report, Sandvine, Inc. ( Traffic share by application (Peak Period) Rank Upstream Downstream BitTorrent 4.% HTTP.7% HTTP.6% Netflix.6% Gnutella.8% YouTube 9.85% 4 Netflix 4.4% BitTorrent 8.9% 5 Skype.8% Flash Video 6.4% 6 SSL.99% RTMP 6.% 7 YouTube.47% itunes.58% 8 MGCP.46% Facebook.44% 9 PPStream.4% Gnutella.% Facebook.8% Xbox Live.6%

4 Mbps Mbps Engineering for IP Video 6 4 seconds of SDTV Traffic Policing Delete packets above threshold Performance suffers due to increased packet loss 8 4 seconds of SDTV Video packets become useless after a certain delay It is better to drop packets earlier (and free some bandwidth) rather than deliver late (and drop at the destination anyway) Traffic Shaping Delay packets above threshold Adaptive TE Use scheduling to allow higher rate, such that delay is enforced Performance suffers due to increased delay / jitter Best performance network can provide Enforced delay bound Need to intelligently combine scheduling, shaping and policing to accommodate busrty traffic

5 Capacity Sharing is Crucial Data/video traffic is bursty at many timescales (second-order self-similar). Burst size distribution is long-range dependant (heavy tailed): most bursts are small, but most bytes arrive in large bursts. From a byte point of view, network is always busy! (!) Static bandwidth assignment is very inefficient Static size is not enough when a burst arrives Static size is underutilized between bursts Output Stream Guaranteed fixed capacity = 5 Mbps (65-byte / ms) Buffer Input Stream Link rate = Mbps Average arrival rate = Mbps Unused Times (bytes) Queue Size (bytes) Arrivals (bytes) 4,,5,,5 6,5,, 6,5 4 5 ms 4 5 ms 4 5 ms In this experiment, the egress capacity =.5 x ingress load. Still, the queue has grown to 4 Kbytes. 4

6 EPON is Designed for Dynamic Sharing Downstream Data stream from the OLT reaches all s 8. Frames extracted by s. USER Upstream OLT USER To avoid collisions, s transmit in nonoverlapping times No packet fragmentation USER Bandwidth assignment is done using GATE and REPORT messages OLT time REPORT tells OLT how many bytes are waiting in s queues time time GATE tells when and for how long it may transmit. GATE message REPORT message time 5

7 Delay (s) Bytes Static vs. Dynamic Bandwidth Assignment Comparison of Static Slot Assignment (SSA) with Dynamic Slot Assignment (DSA) in a PON o Under SSA, avg. delay and avg. queue size ~ 5- times exceeds those under DSA Average Packet Delay Average Queue Size.E+8.E+6...E+4. SSA DSA.E+ SSA DSA Offered Load.E Offered Load 6

8 Shared vs. Dedicated Capacity Dedicated (Fixed) Capacity Shared (Variable) Capacity Point-to-Point Ethernet G-EPON ch. Gb/s GE Aggr. SW GE GE GE GE GE Gb/s s OLT Power Splitter GE GE GE GE GE ch. Gb/s Aggr. SW WDM-PON OLT AWG GE GE GE GE Let s compare performance of three access architectures: Point-to-point GE ( GE ports) WDM-PON ( Gb/s channels) G-EPON (Gb/s shared among channels) Run simulation tests with bursty traffic and non-uniform load (% of users generate 8% of traffic) 7

9 Gbps ms Loss Rate Sharing Is Good Total Throughput Avg. Packet Delay in Busy Packet Loss in Busy. 8. G-EPON GE-PP G-EPON GE-PP G-EPON GE-PP Total Offered Load (Gbps) Total Offered Load (Gbps) Total Offered Load (Gbps) (!) EPON with Gb/s of aggregated capacity outperforms PP Ethernet or WDM-PON with Gb/s of aggregated capacity Ability to instantaneously redistribute capacity among busy users is the main advantage of TDMA-PONs (EPON and GPON) In PP Ethernet case (or in WDM-PON), each switch is confined to its fixed pipe. 8

10 Thank You 9