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Scheduling and Quality of Services (QoS) Advanced Telecommunication Network (ET5187) by Aris Cahyadi Risdianto 23210016

Advanced networking - scheduling and QoS part 1

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Page 1: Advanced networking - scheduling and QoS part 1

Scheduling and Quality of Services (QoS)

Advanced Telecommunication Network(ET5187)

byAris Cahyadi Risdianto

23210016

Page 2: Advanced networking - scheduling and QoS part 1

Scheduling and QoS

Input ===> ===> Output (Controller)

Scheduling and QoS

Page 3: Advanced networking - scheduling and QoS part 1

Packet Classification

• Same Class / No Class differentiation > FIFO/LIFO > Most Common Used

• Different Class > Lost Sensitive and Delay Sensitive > Different rules for different Class

Page 4: Advanced networking - scheduling and QoS part 1

Queuing System

I = class of service of K and J flowsMi(t) = actual service allocated for class i at t timeNi(t) = Buffer size

Page 5: Advanced networking - scheduling and QoS part 1

Loss Sensitive Scheduling

Two different Class (High and Low), for the each same class use FIFO with K buffer• Head of line (HoL)• Partial Buffer Sharing (PBS)• Push Out Buffer (POB)• Random Early Detection (RED)

Page 6: Advanced networking - scheduling and QoS part 1

Buffer Size

Familiar and Famous for ATM network

D* = Delay constraint end to end (Based on ITU) -> 10 msE(H) = average number hops ( <10)M = maximum service rate for STM-1 155 Mbps = 366800 cellsK <= M x D*/10 ms

K small, assured delay but loss cell

Page 7: Advanced networking - scheduling and QoS part 1

Head of Line

• Known as priority queue for queueu > 2• Always served High priority cells in the buffer• pre-emptive and non pre-empetive

Same as :

H3 | L5 | L4 | H2 | L3 | H1 | L2 | L1 => HoL

L5 | L4 | L3 | L2 | L1 | H3 | H2 | H1 => FIFO

Page 8: Advanced networking - scheduling and QoS part 1

Partial Buffer Sharing

• The rule specified by threshold T in the queue• Nq(t) is number cells/packet at the time T• Nq(t) < T, high and low enter the queue• Nq(t) > T, only high enter the queue• Nq(t) = K, buffer is full, arriving cells discarded

Page 9: Advanced networking - scheduling and QoS part 1

Push Out Buffer

• Avoid complex determination of best position• Only operates when the buffer is full

LIFO FOB R FOB FIFO FOB

H3 ==> | L5 | L4 | H2 | L3 | H1 | L2 | L1

Page 10: Advanced networking - scheduling and QoS part 1

Random Early Detection (RED)

• Like PBS but have 2 threshold Tmin and Tmax• q < Tmin => no packet drop• q > Tmax => all packet are dropped• Tmin < q < Tmax => packet are drop with P = (q-

Tmin) * Pmx / Tmax-Tmin• used for TCP flows congestion avoidance• variant of RED is WRED (Weighted RED)

Page 11: Advanced networking - scheduling and QoS part 1

Delay Sensitive Scheduling

• Assumption there is no problem of losing packet and buffer k is long

• Consist of processor sharing example WRR has class k with weight Wk

• WRR (Processing sharing) inflexible because Wk independent

• Processing rule rather than processing sharing

Page 12: Advanced networking - scheduling and QoS part 1

Upper Bound Method

• Used for solving CAC (Call Admission Control) problem

• Some assumption : o Each arrival process satisfies with certain

business constraino Service time for cell/packet is deterministic and

proportionalo Scheduling rule is used to generate QoS for

class k with minimal Mk ("fair" rule to prevent blocking another class getting served)

Page 13: Advanced networking - scheduling and QoS part 1

Upper Bound Method (Cont.)

• Queue count is maximum difference between inflow and outflow (λk and μk)

• If queue > 0, class served by minimal rate (μk)• Number of queue bounded by burstinest σk

provided if λk ≤ μk• Buffer size bounded by sum of burstinest all flows,

so loss can be guaranteed• Maximum delay bounded by burstinest divide by

inflows, so delay can be guaranteed

Page 14: Advanced networking - scheduling and QoS part 1

Upper Bound Method (Cont.)

• Remarks on upper bound method :• Zero packet loss only guaranteed for admitted

packet (satisfied with burstinest constrain), if not packet will be lost

• Delay guaranteed are deterministic because all stochastic assumed to be bounded or deterministic

• Upper Bound Method more optimal than N*D/D/1 queuing for scenario where N not identical and independent CBR resources

Page 15: Advanced networking - scheduling and QoS part 1

QoS (Quality of Services)

Page 16: Advanced networking - scheduling and QoS part 1

Evolution and Importance

• Internet and Value Added Services is the main driver

• Internet used for e-commerce, self backing and communication

• Overall result : people are tolerant about QoS, in certain point some people are frustrated of losing data

• Mature Internet need to offer ubiquitous inexpensive, and high quality services

Page 17: Advanced networking - scheduling and QoS part 1

QoS as Technological Lever

• Two Main Approach :

o Over Installing resources (less than 30% load)o Controlling Traffic in the network to ensure each

flows achieve certain level of QoS• QoS implementation is faster and cost effective

than expanding new network (Fiber, equipment, etc)

Page 18: Advanced networking - scheduling and QoS part 1

QoS as Commercial Lever

• Old view: over dimension network without complex network functionality

• Notation QoS : demand always beyond supply cause congestion

• QoS offer dividing resources, not guarantee quality (lower priority users get less, high priority users get more)

• Controlling QoS = Controlling Resources• Sub-optimal controlling resource = loss revenue

Page 19: Advanced networking - scheduling and QoS part 1

Definition and Property of QoS

• In general, QoS express set of service example performance, availability, reliability and security

• Network QoS on layer 3 (inspired by ATM network)

• Application Layer QoS associate with GoS• QoS provision cause dichotomy “soft” and “hard guarantee”

• Perceived QoS (Voice, Streaming, e-games): delay, jitter, echo, packet loss

Page 20: Advanced networking - scheduling and QoS part 1

Challenges : QoS aware Networking

• Main Problem : Stochastic arrival process and deterministic set of traffic or determination

• Analysis and computing random variable more complex

• Computation level explode state spaces and prevent accurate computations

• Inherent problem “connection set-up time” need QoS per flow such as QoS routing, signalling and CAC

• Two different future QoS by IETF : IntServ and DiffServ

Page 21: Advanced networking - scheduling and QoS part 1

Evolution Network Architecture : IP and ATM

• Two different approach : IP by IETF and ATM by

ATM forum• Layered routing : IP for L3 and ATM for L2• Integration :

• Partially Integrated : Dual-Mode• Fully Integrated : I-PNNI• Ipsilon : ATM for forwarding, IP for control• IETF : MPLS (IP Fast Switching)

• ATM goal, reality of IP : Basic Architecture for Broadband Multimedia

Page 22: Advanced networking - scheduling and QoS part 1

QoS Emerging in the Internet

• QoS aware networking including QoS routing, signaling and traffic management

• Standardized by IETF but not implemented• QoS aware Internet:

• RSVP : signaling• IntServ : end-to-end signaling per flow basis• DiffServ : no end-to-end signaling per flow

Page 23: Advanced networking - scheduling and QoS part 1

RSVP

• RSVP (Resource Reservation Protocol)• IETF signalling protocol based on multicast• Used two types of messages : path and reservation

messages• Most of Telecom or connection oriented based on

unicast• Continued with SIP protocol as application layer

signalling protocol

Page 24: Advanced networking - scheduling and QoS part 1

RSVP Messages

• Path messages : previous hop IP address, sender template and IP address, traffic characteristic, end to end QoS requirement

• Teardown Messages : Path Tear and Resv Tearo Path Tear : Iniated by the sender to install

reservation stateo Reservation Tear : Travels from receiver to the

sender to remove reservation state

Page 25: Advanced networking - scheduling and QoS part 1

RSVP Operations

• Sender send path message to receiver of the mcast group, each router install the reservation state and record the hop

• Receiver send "Resv Message" to nearest router and ask amount of resources

• Nearest Router reserve along the path to the sender

• If other receiver joint the mcast group, nearest router ask more resource along the path

Page 26: Advanced networking - scheduling and QoS part 1

Characteristic of RSVP

• Used for unicast and multicast application• Receiver Oriented : flows initiated and resources

reservation• Consist of policy control and admission control• MPLS LDP is alternate to RSVP based on explicit

routing• QoS state is soft state : messages are flows

periodic to adopt the routing changes• reservation for unidirectional data flows

Page 27: Advanced networking - scheduling and QoS part 1

Integrated Services (IntServ)

• Additional component : packet classifier, scheduler and admission control

• Required resources reservation for each session/flows using RSVP

• If RSVP failed, the session will be best effort (BE)• Two class:

o Guaranteed Services : provide services with guaranteed both delay and bandwidth

o Controlled-Load Services : provide data flow all same in the unloaded network, and using CAC if network is loaded

Page 28: Advanced networking - scheduling and QoS part 1

Differentiated Services (DiffServ)

• Threat each class differently on per-hop behaviour (PHB)

• Class differentiation rather than flow differentiation (more scalable)

• Provide QoS more natural than IntServ which inline with Internet

• Bandwidth Broker use to managed inter-domain resources for providing end-to-end QoS

Page 29: Advanced networking - scheduling and QoS part 1

Differentiated Class

• IP DSCP format:

• Two different PHB Class, except BE (Best Effort) : Expedited Forwarding (EF) = virtual leased line or

point-to-point connection Assured Forwarding (AF) = better best efforf

Page 30: Advanced networking - scheduling and QoS part 1

Next on "Scheduling"

• Generalized Processing Sharing (GPS)• Generalized cu-rules (Dynamic Scheduling

Rules)

Page 31: Advanced networking - scheduling and QoS part 1

Next on "Quality of Services"

• Shortcut Routing : L2 over L3 (MPLS)• Multiprotocol Label Switching (MPLS)

including GMPLS (Generalized MPLS)