Network layer

Doug Young Suhsuh@khu.ac.kr

Last update : Aug. 1, 2009

Network Layer

Network layer and realtime multimedia

Protocols for switching in the routersRouting = path + resource

cf) direction + width of road

IP header : IPv4 and IPv6New features in IPv6

Best Effort per-class per-flowintServ. diffServ, MPLS

23年 4月 19日 MediaLab , Kyunghee University

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Networked Video

QoS control for networked video

Physical Layer

Data Link Layer

Network Layer

Transport Layer

Upper Layers

(Video Layer)End-to-end

Error resilience/concealment, scalability codingUDP/RTP&RTCP, FEC, retransmission

IP TOS, RSVP, intServ

FEC, retransmission, MAC

Power control

Networked Video

Network layer approaches

RSVPintServdiffServMPLS

Transport Layer

Over-provision or QoS control?Internet service will be charged.IPv6 doesn't give a solution for the QoS

issue. IPv6 has the potential.

Video Layer

Categories of QoS protocols

Circuit switching or broadcasting • Fixed QoS• Dedicated circuit for a call e.g. telephone

Network QoS

Packet switching • Variable QoS (Best Effort)• Resource sharing e.g. downloading data

QoS switching • Guarantee reserved QoS• Resource allocation (dynamic) e.g. realtime service

QoS switching1.Per-class (coarse) : Packets are classified into several classes. 2.Per-flow (fine) : A flow could be a media stream of a certain service. Call admission control is required for resource reservation with all routers along the path.

Per-class and per flow QoS services

I’m a class B packet.

You, use the Gate

B.

I’m a video packet for the video-phone

service between John and Susan.

We provide you QoS of

[5Mbps, 10-5 packet loss,

and 1ms delay].

After reading the temporary customer list

for identification,,,,

,,,

Per-class QoS service

Per-flow QoS service

router

router

QoS identification for every video packet

per-class QoS : 8 bit TOS (TC) in the IP header

BA (behavior aggregate) classifier PHB : EF and AF(4 classes with 3 levels)

per-flow QoSEach flow has a temporary contract on QoS.IntServ : identified by 5 tuples

• 104 bits IPv4, 296 bits IPv6MPLS : identified by label

SA DA SP DP Pr data

Admission control

Packetscheduler

classifier

data

SA DA SP DP Pr TSpec1SA DA SP DP Pr TSpec2SA DA SP DP Pr TSpec3SA DA SP DP Pr TSpec4SA DA SP DP Pr TSpec5

intServ routing table

label

BA

classifier

PHB1

PHB2

PHB3

RSVP/intServ

CAC by RSVP, call control by intServ

Networked Video

RSVP parameters

Tspec (PATH), Rspec (RESV) r : token rateb : token-bucket depthp : peak ratem : minimum policed sizeM : maximum packet size

Leaky bucket model [r,b], [p,M]

Networked Video

Resource reservation

When realtime service needs excess bandwidth, non-realtime service packets are buffered.

Networked Video

Diffserv Architecture

Edge router:- per-flow service

- marks packets of in- or out-profile

Core router:

- per class service

- buffering and scheduling

- preference to in-profile packets- Assured Forwarding

CR scheduling

...

r

b

ER markingBandwidth Broker

Networked Video

ER : Traffic Conditioning

• Classifier of micro-flow w.r.t. agreed traffic profile• Marker : low, medium, high drop precedence

Networked Video

CR : traffic management

BA (behavior aggregate) classifier PHB

EF : guaranteed service, WFQ (weighted fair queuing)AF : 4 classes with 3 levels (high, medium, low drop procedure levels), RED (random early discard)

BA

classifier

PHB1

PHB2

PHB3

History of video/network

Packet switching :Packet switching :Best effortBest effort

per class QoSper class QoS Per flow QoSPer flow QoS~AVC

SVC

??Circuit switchingCircuit switching

BroadcastingBroadcasting

H.261MPEG-2

IPv4IPv42G2G

IPv6IPv63-4G3-4G

MPEG-4& AVC 200

8

No QoS control, because

everything is fixed.

No QoS control, because

network does not care.

Coarse QoS control, [premium, medium, low,

etc.]

Fine QoS control, each

media traffic of each individual

service

Revisit QoS of upper layers.Video layer

Feedback rate control Realtime encoding : quality vs. bitrate (R-D)Non-realtime encoding : Scalable coding

VBR(natural) and CBR(forced rate control)Multiple levels of significance

Partition A, B, C in a frameIntra > predictive > bi-directionalScalable coding : base layer > enhancement layers

Error propagation and error resilience

Transport layerFeedback of QoS metrics : loss/delay/bitrateFEC : UEP/ULP (unequal error/loss protection)

23年 4月 19日 MediaLab , Kyunghee University

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Networked Video

IPv6 (IPng)

128 bit address => 181018nodes, 4 nodes/cm2

Ubiquitous networksHierarchical addressesmulticast, anycast => QoS aware broadcasting

Simplified header (for realtime sevice)Improved securityAuto-configuration

plug-play network access (DHCP, ND)micro-mobility

QoS awareness traffic class (8 bits) flow label (20 bits, cf. VC of ATM)

Networked Video

Header formats of IPv4/IPv6

Version(4)

TrafficClass (8)

Flow Label (20)

Payload Length (16)Next

Header (8)Hop

Limit (8)

Source Address (128)

Destination Address (128)

Version(4)

HLEN(4)

Type ofService (8)

Total Length (16)

Identification (16)Flags(3)

FragmentOffset (3)

TTL (8) Protocol (8)Header Checksum

(16)

Source IP Address (32)

Destination IP Address (32)

Networked Video

IPv6 is reality.

Worldwide IPv6 network : tunneling-basedIPv6 routers : 3Com, Compaq, Ericsson Telebit, Hitachi Ltd., Nokia Telecom, Northern Telecom,IPv6 Linux kernelWindows NT, Windows 2000Future : wireless services in China, ubiquitous network

Multicast in IPv6

T : permanent (0) or transient (1)Scope : geographic scope (within node~global)

111111111000T Scope Multicast group address 8 4 4 104 8

Networked Video

Anycast in IPv6

010 Reg. TLA NLA SLA Interface ID

3 5 8 32 16 64

TLA, NLA, SLA : aggregatorsAnycast : A group of hosts or

routers can have the same address and provide the same service. Clients are connected to the nearest server. (cf: local broadcasting stations)

anyTV.co.kr

Networked Video

MIPv6 multimedia service

IntServ/RSVP

Network Layer

QoS Support in the InternetCall admission control (CAC) traffic policing

by using signaling protocolTraffic characteristics and requirements

Traffic shaping : User’s effort to keep promiseTraffic policing : Router’s effort to police

Network Layer

CAC

Trafficshaping

Trafficpolicing

Scheduling (queuing) algorithms

FIFO (First In First Out)Weighted fair queuing (WFQ)Deficit round robin (DRR)Stochastic fair queuing (SFQ)Round robin (RR)Strict priority

Network Layer

ReSource reserVation Protocol (RSVP)

Previously, RFC1819 Internet Stream Protocol v2 (ST2+) referred as “IPv5”RFC 2205 RSVP (1997)

RSVP and intServ : RFC 2210Signaling to reserve resource along the path of particular data streams or flows

Unicast and multicastMultipoint to multipointMultipoint to single point

Network Layer

Host RouterRouterRouter HostPATH PATH PATH PATH

RESVRESVRESVRESV

“PATH” and “RESV” Messages

“PATH” : from source to targetMarks the routed path and collects information about the QoS viability of each router along the path

“RESV” : from target to sourceIt the target wants, reserves resources along the path

Routers can “merge” downstream reservations to the same stream.State is maintained as long as “PATH” and “RESV” messages flow.Receiver driven (compared to broadcasting)

Large group, dynamic group membership, heterogeneous receiver requirements “dynamic”=soft state : created/modified/removed

Network Layer

RSVPWhat I am

originating application and sub-flow such as print flow vs. time-critical transaction

Who I am authenticated user ID

What I wantthe type of QoS service needed

How much I want certain applications quantify their resource requirements precisely.

How I can be recognized the 5-tuple classification criteria by which the data traffic can be recognized

Which network devices resources will be impacted by the associated data traffic

Network Layer

RSVP modules in hosts and routers

ApplicationRSVP processAdmission control : sufficient available resources for the request?

Policy control : whether the use has permission for the reservation?

Network Layer

Appli-cation

RSVPprocess

Policy control

Admission control

Packetscheduler

classifier

data

data

Routingprocess

RSVPprocess

Policy control

Admission control

Packetscheduler

classifier

data

Host Router

intServ

control

control

RSVP

Reservation Request Spec.sFilter spec. (logical)

Selection of subsets of the packets of a given sessionSender IP address and source portTo set parameters in the packet classifier

Flow spec. (quantitative)Specification a desired QoS

Service classTspec (traffic descriptor)Rspec (desired QoS parameters)

To set parameters in the node’s packet scheduler

Network Layer

RSVP parametersTspec (PATH), Rspec (RESV)

r : token rateb : token-bucket depthp : peak ratem : minimum policed sizeM : maximum packet size

Double leaky bucket model [r,b], [p,M]

Network Layer

p

bp

rb

r<b

<M

pVBR : average rate < r < pCBR : average rate = r = p

Tspec/Rspec in RFC2210

Network Layer

Guaranteed serviceControlled load

RSVP Styles

Fixed-filterAll sender are active at all time.

S1 S2

N

R

ff

2f

S1 S2

N

R

ff

f

One sender at a time Wildcard-filter

e.g. audio conferencing

Shared explicit The receiver select a

sender.

sender

filter

receiver

router

Scalability Problem3 step processes for every intServ packet1. Identification of an intServ packet by 5 tuple classifiers

{(SA, DA), (source port #, receiver port #), protocol}

2. Searching for the service spec. for the packet

3. Traffic policing and scheduling

Impossible inside core network Maybe possible in edge routers of mobile network

Network Layer

Admission control

Packetscheduler

classifier

data

SA DA SP DP Pr TSpec1SA DA SP DP Pr TSpec2SA DA SP DP Pr TSpec3SA DA SP DP Pr TSpec4SA DA SP DP Pr TSpec5

intServ routing table

5-tuples in IPv4 and IPv6

Network Layer

Flow ID : 104 bits in IPv4 and 296 bits in IPv6 IPv4 104 = 32*2 (SA, DA) + 32(SP, DP) + 8

(protocol) Scalability problem in public network ~NN

Class ID : 6 bits in DS field diffServ

Networked Video

MPLS (Multi-Protocol Label Switching)

Scalability problem of intServA set of 5 tuples a temporary labelVirtual switch for the efficiency of routers (cf. ATM)

Connection oriented : VC (Virtual Circuit)VC lookup table (resource, path)

Routing flexibilityTraffic engineering and provisioningConstraint-based routing (QoS routing)FEC (Forward Equivalence Class)

With RSVP

IPv6 “Flow Label”

ConclusionsintServ for per-flow service IEEE801.16, UMTS~

RSVP for resource reservationControlled load, guaranteed service

CAC traffic shaping / policing

Scalability problemMPLS, IPv6 flow label for simplified identification

Advanced approachRFC4495 “RSVP Extension for Reduction of Bandwidth” (2006)Draft-intserv-multiple-tspec (2010)

“…. to dynamically adapt to available bandwidth…”Multiple reservations between two endpointsRefreshes only include the Tspecs that were accepted

23年 4月 19日 MediaLab , Kyunghee University

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