1 Flow-Aware Networking Introduction Concepts, graphics, etc. from Guide to Flow-Aware Networking: Quality-of-Service Architectures and Techniques for Traffic Management (Jerzy Domżał Robert Wójcik Andrzej Jajszczyk)

Flow-Aware Networking Introduction 2 What is Flow-Aware Networking (FAN)? A relatively new architecture for Quality of Service in the Internet A relatively new architecture for Quality of Service in the Internet –provides an approach to providing class of service differentiation similar to that envisioned by IntServ –is a simple, straight-forward enhancement to the current IP network architecture Key characteristics/advantages Key characteristics/advantages –scalable and simple –“net neutral” –does not require signaling, e.g. RSVP for IntServ (out-of-band) RSVP for IntServ (out-of-band) DSCP for DiffServ (in-band) DSCP for DiffServ (in-band)

Flow-Aware Networking Introduction 3 What is Flow-Aware Networking (FAN)? Goal: Enhance the current IP network by improving its performance under heavy congestion Goal: Enhance the current IP network by improving its performance under heavy congestion Key Operational Concepts: Key Operational Concepts: –measurement-based admission control provide assurance of a minimal performance level for each flow provide assurance of a minimal performance level for each flow –fair scheduling with priorities fair distribution of available bandwidth fair distribution of available bandwidth negligible latency for well-behave flows negligible latency for well-behave flows

Flow-Aware Networking Introduction 4 FAN Compared ARCHITECTUREPROSCONS Integrated ServicesReal service guaranteesLow/weak scalability Differentiated Services Scalable, simple Limited/fixed classes of service (per domain) Flow-Aware Networking No signaling, simple Weak service differentiation

Flow-Aware Networking Introduction 5 FAN Operation: Cross-Protect Router Functions 1. Classify all incoming packets into flows (note: this is not a service classification, but simply recognition of a unique flow of traffic) 2. All previously identified flows appear in the Protected Flow List (PFL) and are forwarded (scheduled) unconditionally. 3. New flows are subjected to Measurement-Based Admission Control (MBAC).

Flow-Aware Networking Introduction 6 FAN Operation: Cross-Protect Router Functions 4. MBAC function forwards or drops packets in flows not on PFL based on current link congestion conditions –Reasonable level of congestion, capacity available: add flow to PFL and add to queue –Congestion above threshold: drop packets

Flow-Aware Networking Introduction 7 FAN Operation: What Defines a “Flow?” A unique instance of a set of identifiers in the IP header A unique instance of a set of identifiers in the IP header –Source/destination IP addresses –Source/destination port numbers –Transport protocol number –Ipv6 flow label field –Etc. Provider-specified based on user population, application types supported, etc. Provider-specified based on user population, application types supported, etc.

Flow-Aware Networking Introduction 8 FAN Operation: What Defines a “Flow?” Internet traffic is composed of flows Internet traffic is composed of flows –same identifier, minimum packet spacing –flows are "streaming" or "elastic" –streaming service: "conserve the generated signal" –elastic service: "transfer as fast as possible" The essential characteristic: the flow peak rate The essential characteristic: the flow peak rate –streaming peak rate = application rate –elastic peak rate = exogenous rate limit (access line, burstiness, …)

Flow-Aware Networking Introduction 9 FAN Operation: What Defines a “Flow?” All admitted flows are characterized in one of two classes: All admitted flows are characterized in one of two classes: –Streaming: those producing traffic at lower than the current fair rate –Elastic: those with traffic at a rate higher than the current fair rate

Flow-Aware Networking Introduction 10 Flow Treatment (QoS) Compared QoS Architecture Flow Definition Basis QoS Treatment of a Flow Integrated Services Distinct user activity All packets within a defined flow must be treated equally per the specified QoS (Rspec). Differentiated Services Src IP, Dest. IP & DSCP All packets within each defined aggregate of flows must be treated per a defined class of service. Flow-Aware Networking IPv4 5-tuple or IPv6 Flow # All admitted flows are treated fairly with regard to other admitted flows based on current peak rate of the flow and the state of network congestion

Flow-Aware Networking Introduction 11 FAN Operation: Differentiation of Service Streaming flows: those producing traffic at lower than the current fair rate Streaming flows: those producing traffic at lower than the current fair rate –these flows receive prioritized treatment –packets of these flows are sent through priority queues (PFQ, or PB-DWRR) –hence, low delays and delay variations Elastic flows: those with traffic at a rate higher than the current fair rate Elastic flows: those with traffic at a rate higher than the current fair rate –fair queuing: fair bandwidth sharing with other elastic flows (better than FIFO)

Flow-Aware Networking Introduction 12 FAN Operation: Cross-Protect Router Streaming Flows Elastic Flows

Flow-Aware Networking Introduction 13 FAN Operation: Cross-Protect Router

Flow-Aware Networking Introduction 14 FAN Operation: MBAC Measurement-Based Admission Control (MBAC) Measurement-Based Admission Control (MBAC) –per-flow measurement –existing flows are not subjected to MBAC –each new flow receives identical treatment –when network congestion, at a cross- protect router, reaches a specified threshold, new flows are blocked

Flow-Aware Networking Introduction 15 FAN Operation: MBAC MBAC Measurements Fair Rate (FR) Fair Rate (FR) –estimate of current rate of backlogged flows –minFR is lower-bound threshold Priority Load (PL) Priority Load (PL) –the capacity currently allocated to streaming (priority) flows –maxPL is upper bound threshold

Flow-Aware Networking Introduction 16 FAN Operation: Scheduling Scheduling Scheduling –Two proposed algorithms: Priority Fair Queuing (PFQ): uses Push-In, First-Out (PIFO) approach 1 Priority Fair Queuing (PFQ): uses Push-In, First-Out (PIFO) approach 1 Priority Deficit Weighted Round-Robin (PB- DWRR): using quantum-based weighting in queues with different priorities Priority Deficit Weighted Round-Robin (PB- DWRR): using quantum-based weighting in queues with different priorities –Both algorithms have, logically, one priority queue and a secondary queuing system –Both are scalable as link capacity and load increase 1. See A. Kortebi, S. Oueslati, and J. W. Roberts, “Cross- protect: implicit service differentiation and admission control,” in Proc. High Performance Switching and Routing, HPSR 2004, Phoenix, AZ, USA, 2004, pp. 56–60)

Flow-Aware Networking Introduction 17 FAN Operation: Summary Applies per-flow fair queueing in router queues Applies per-flow fair queueing in router queues Maintains awareness of "active" flows (a small number!) Maintains awareness of "active" flows (a small number!) Applies per-flow admission control in case of overload Applies per-flow admission control in case of overload Maintains awareness of "in-progress" flows (a large number) Maintains awareness of "in-progress" flows (a large number)

Flow-Aware Networking Introduction 18 FAN Advantages: Summary Retains the current best effort user- network interface… simple extension to current IP routing procedures and infrastructure Retains the current best effort user- network interface… simple extension to current IP routing procedures and infrastructure Flow-awareness allows enhanced protection of critical user data Flow-awareness allows enhanced protection of critical user data Admission control allows adaptive routing Admission control allows adaptive routing Performance assurance provided for both streaming and elastic traffic through implicit service differentiation Performance assurance provided for both streaming and elastic traffic through implicit service differentiation

Flow-Aware Networking Introduction 19 FAN Advantages: Summary Supports TCP, but fair queueing approach removes the need for "TCP friendliness“ and eliminates “UDP greediness” Supports TCP, but fair queueing approach removes the need for "TCP friendliness“ and eliminates “UDP greediness” Support reductions of operating and capital expenses, Support reductions of operating and capital expenses, Simplifies service provider billing Simplifies service provider billing