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1 © 2013 Cisco and/or its affiliates. All rights reserved. An Improved Hop-by-hop Interest Shaper for Congestion Control in Named Data Networking Yaogong.

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Presentation on theme: "1 © 2013 Cisco and/or its affiliates. All rights reserved. An Improved Hop-by-hop Interest Shaper for Congestion Control in Named Data Networking Yaogong."— Presentation transcript:

1 1 © 2013 Cisco and/or its affiliates. All rights reserved. An Improved Hop-by-hop Interest Shaper for Congestion Control in Named Data Networking Yaogong Wang, NCSU Natalya Rozhnova, UPMC Ashok Narayanan, Cisco Dave Oran, Cisco Injong Rhee, NCSU

2 2 © 2013 Cisco and/or its affiliates. All rights reserved. Data packets assumed to consume bandwidth Too many data packets cause congestion Congestion detected by monitoring data packet transfer Queue depth in midpoint, delay and/or loss (modulo ECN) at endpoint Assumes that non-data traffic (TCP ACKs) don’t cause congestion Reasonable, since ACK is 40 bytes and full TCP frame is 1460 bytes

3 3 © 2013 Cisco and/or its affiliates. All rights reserved. Two important factors to consider: 1. Receiver-driven: one interest generates one data packet 2. Symmetric: Content retrieved in response to an interest traverses the same path in reverse Content load forwarded on a link is directly related to interests previously received on that link Given these properties, shaping interests can serve to control content load and therefore proactively avoid congestion. There are multiple schemes that rely on slowing down interests to achieve congestion avoidance or resolution But, detecting the congestion in question is not simple Because it appears on the other side of the link where interests can be slowed

4 4 © 2013 Cisco and/or its affiliates. All rights reserved. Different schemes have been proposed HoBHIS First successful scheme, demonstrated the feasibility of this method Slows down interests on the hop after congestion Relies on backpressure to alleviate congestion ICP/HR-ICP Runs per-flow AIMD scheme to manage outstanding interests Tracks estimated RTT as a mechanism to rapidly detect congestion & loss Endpoints control flow requests by shaping interest issue rate Main congestion control operates end-to-end, some hop-by-hop shaping for special cases

5 5 © 2013 Cisco and/or its affiliates. All rights reserved. Assume constant ratio r of content-size/interest-size Simple unidirectional flow with link rate c Ingress interest rate of c/r causes egress content rate of c If we shape egress interest rate to c/r, remote content queue will not be overloaded Issues with varying content size, size ratio, link rate, etc. But the biggest issue is…

6 6 © 2013 Cisco and/or its affiliates. All rights reserved. Interests consume bandwidth (specifically, c/r in the reverse direction) Bidirectional data flow also implies bidirectional interest flow Therefore, the reverse path is not available to carry c bandwidth of data, it also needs to carry some interests And similarly, the rate of interests carried in the reverse direction cannot budget the forward path entirely for data, it needs to leave space for forward interests as well Ordinarily there is no way to predict and therefore account for interests coming in the other direction, but… There is a recursive dependence between the interest shaping rate in the forward and reverse directions.

7 7 © 2013 Cisco and/or its affiliates. All rights reserved.

8 8 We can formulate a mutual bidirectional optimization as follows u(.) is link utility function This must be proportionally fair in both direction, to avoid starvation We propose log(s) as utility function i 1 = received forward interest load i 2 = received reverse interest load c 1 = forward link bandwidth c 2 = reverse link bandwidth r 1 = ratio of received content size to sent interests size r 2 = ratio of sent contents size to received interests size

9 9 © 2013 Cisco and/or its affiliates. All rights reserved. Feasible region is convex First solve for infinite load in both directions Optimal solutions at the Lagrange points marked with X If Lagrangian points do not lie within feasible region (most common case), convert to equality constraints and solve

10 10 © 2013 Cisco and/or its affiliates. All rights reserved. Optimal shaping rate assumes unbounded load in both directions We can’t model instantaneously varying load in a closed-form solution If one direction is underloaded, fewer interests need to travel in the reverse direction to generate the lower load As a result, the local shaping algorithm need not leave as much space for interests in the reverse direction Extreme case: unidirectional traffic flow Actual shaping rate needs to vary between two extremes depending on actual load in the reverse path BUT, we don’t want to rely on signaling reverse path load

11 11 © 2013 Cisco and/or its affiliates. All rights reserved. We observe that each side can independently compute both expected shaping rates Our algorithm observes the incoming interest rate, compares it to the expected incoming interest shaping rate, and adjusts our outgoing interest rate between these two extremes On the router, interests and contents are separated in output queues. Interests are shaped as per the equation above, and contents flow directly to the output queue.

12 12 © 2013 Cisco and/or its affiliates. All rights reserved. When an interest cannot be enqueued into the interest shaper queue, it is rejected Instead of dropping it, we return it to the downstream hop in the form of a “Congestion-NACK” This NACK is forwarded back towards the client in the place of the requested content Consumes the PIT entries on the way Note that the bandwidth consumed by this NACK has already been accounted for by the interest that caused it to be generated Therefore, in our scheme Congestion-NACKs cannot exacerbate congestion Clients or other nodes can react to these signals In our current simulations, clients implement simple AIMD window control, with the NACK used to cause decrease

13 13 © 2013 Cisco and/or its affiliates. All rights reserved. Scenario Data Throughput (Mbps) Data loss (%) Interest rejection rate (%) Client 1Client 2R1R2Client 1Client 2 Baseline 25B Interest, 1KB Data 9.558 ±0.001 9.559 ±0.002 000.015 ±0.0006 0.015 ±0.0011 Varying Pkt Size Data from 600-1400B 9.432 ±0.005 9.434 ±0.008 000.018 ±0.0014 0.017 ±0.0015 Asymmetric data size 1000B/500B 9.373 ±0.014 9.326 ±0.001 000.007 ±0.0006 0.016 ±0.0006 Asymmetric bandwidth 10 Mbps/1 Mbps 9.774 ±0.001 0.719 ±0.001 000.012 ±0.0005 0.058 ±0.0000

14 14 © 2013 Cisco and/or its affiliates. All rights reserved. Scenario Data Throughput (Mbps) Data loss (%) Interest rejection rate (%) Client 1 Server 3 Client 2 Server 4 R1R2Client 1 Server 3 Client 2 Server 4 Homogeneous RTT5.142 ±0.5 4.692 ±0.5 000.515 ±0.011 0.063 ±0.013 Heterogeneous RTT R2—S4 link now 20ms 5.209 ±0.38 4.624 ±0.38 000.513 ±0.009 0.042 ±0.007 Flipped data flows Client1  Server3, Client4  Server2 9.566 ±0.001 9.419 ±0.007 000.148 ±0.0004 0.012 ±0.0005

15 15 © 2013 Cisco and/or its affiliates. All rights reserved. Queue depth on bottleneck queues is small 1 packet for homogeneous RTT case Varies slightly more in heterogeneous RTT case, but is quite low (<17 packets) Client window evolution is quite fair

16 16 © 2013 Cisco and/or its affiliates. All rights reserved. Optimally handles interest shaping for bidirectional traffic No signaling or message exchange required between routers Corollary: no trust required between peers No requirement of flow identification by intermediaries Fair and effective bandwidth allocation on highly asymmetric links Congestion NACKs offer a timely and reliable congestion signal Congestion is detected downstream of the bottleneck link

17 17 © 2013 Cisco and/or its affiliates. All rights reserved. Use congestion detection and/or NACKs to offer dynamic reroute and multi-path load balancing Use NACKs as backpressure mechanism in the network to handle unco-operative clients Investigate shaper under different router AQM schemes (e.g. RED, CoDEL, PIE) and client implementations (e.g. CUBIC).

18 18 © 2013 Cisco and/or its affiliates. All rights reserved.


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