Senior Consultant Network Planning and Design Siemens AG, München

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T. Bauschert 11.05.2001 1IP Network Engineering Challenges

Senior ConsultantNetwork Planning and DesignSiemens AG, München

Email: [email protected]

Dr. Thomas Bauschert

IP Network Engineering Challenges

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Outline

• Network Architecture• IP Traffic Specification• IP Network Dimensioning• IP Traffic Engineering and QoS Provisioning• Further important Engineering Issues• Special Topic: MPLS - DiffServ: Combination of Traffic

Engineering and QoS Provisioning

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Network ArchitectureNetwork Architecture

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Network Architecture

• State-of-the-art network architecture:• switched (MPLS) IP core network (highly meshed)• multiple homed distribution/access routers

C o r e R o u t e r ( 3 2 0 G )

D i s t r i b u t io nR o u t e r ( 4 0 G )

I n t e r n e tE x c h a n g e

G ig a E t hR i n g

S T M - 1 6 / 6 4 / 3 2 *

R i n gS T M - 4 , G i g a E t h / 3 2 *

S T M - 1

G i g a E t h P a r t i a l l y m e s h e dS T M - 6 4 / 1 6 0

D a t aC e n t e r s

L o c a lE x c h a n g e

1 0 0 b T

A c c e s s R o u t e rA g g r . D e v i c e s

A c c e s sD e v i c e s

M G W

S T M - 1 / 4 ,G i g a E t h

E 1 , E 3 , S T M - 1 L L

D a t a C e n t e rR o u t e r

I n t e r c o n n e c tR o u t e r

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Network Architecture

• Future challenges:• scaleable/reliable network architecture

(to accommodate huge IP traffic growth): Tbit/s-routers required in near future

• switched (MPS) optical core network (ASON): interaction of IP and optical layer (similar to IPoATM)

ATM

virtual meshing via ATM PVCs

router throughput < 1 Gbit/s,STM-16 I/F

router throughput < 1 Tbit/s,STM-64 I/F

physical meshing

ASON

router throughput < 1 Tbit/sn x STM-64 DWDM I/F

virtual meshing via wavelenghts

state-of-the-art future

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IP Traffic SpecificationIP Traffic Specification

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IP Traffic Specification (for Network Planning Purposes)

• State-of-the-art:• traffic model stream/elastic traffic:

stream traffic parameters: offered traffic + effective bitrate elastic traffic parameters: flow arrival rate + average flow size

• traffic matrix generation methodology

Voice Video FTPWWW ...

...

IP TrafficTypes(w/w.o. QoSguarantee)

TrafficClasses

Services/Applications

Traffic Class 1 Traffic Class 2 Traffic Class 3

Traffic ParameterQoS Param. (flow)QoS Param. (packet)

• arrival rate + duration• or: offered traffic• mean + peak bitrate• blocking probability• connection setup delay• packet delay / jitter / loss

• file arrival rate +average file size

• offered traffic volume• average throughput• or: average transfer time

for file of specific size• delay before data transfer• packet delay / jitter / loss

StreamTrafficQoS 1

StreamTrafficQoS 2

ElasticTrafficQoS 1

ElasticTrafficQoS 2

• Challenges:• traffic classification: how many classes are really necessary?• which QoS metrics should be applied? (e.g. blocking

probability for stream traffic is only reasonable in case of CAC) • point-to-multipoint traffic description strong relationship

to QoS mechanisms

UserSite

ServerSite

ISPs /Internet

1)

2)

3)

4)

5)6)

Cache

IP Network

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IP Network DimensioningIP Network Dimensioning

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IP Network Dimensioning

• State-of-the-art:• single link dimensioning with multirate

Erlang-B (stream) and M/G/R-PS (elastic, ideal TCP behavior) model

• dimensioning for tree-type access networks

• separate dimensioning for elastic / stream traffic portions

)1(),(

1)}({ 2

RRRE

rxxTE

peak

a v e r a g e t i m et o t r a n s f e r a f i l e

o f l e n g t h xf i l e l e n g t h

p e a k b i t r a t e u t i l i z a t i o n : = ( · x m e a n ) / C

r a t i o C / r p e a k

dC

dME

MC

BCr

s

s

,1

11

)(

b l o c k i n gp r o b a b i l i t y o ft r a f f i c c l a s s s

b l o c k i n gp r o b a b i l i t y o ft r a f f i c c l a s s s

e f f e c t i v e b i t r a t eo f t r a f f i c c l a s s s

e f f e c t i v e b i t r a t eo f t r a f f i c c l a s s s

t o t a l o f f e r e dt r a f f i c v o l u m et o t a l o f f e r e d

t r a f f i c v o l u m e

b i t r a t e o f t h ee q u i v a l e n t s i n g l e

s e r v e r s y s t e m

b i t r a t e o f t h ee q u i v a l e n t s i n g l e

s e r v e r s y s t e m

s o l u t i o n o f t h ec h a r a c t e r i s t i c

p o l y n o m

s o l u t i o n o f t h ec h a r a c t e r i s t i c

p o l y n o m

carriedstreamtraffic

stream traffic

elastic traffic

blockedstreamtraffic

offeredstreamtraffic

admission control link capacity

offeredelastictrafficvolume

service discrimination(realized by link buffer scheduler)

average TCPthroughput

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IP Network Dimensioning

• Challenges:• link dimensioning model improvements:

- dimensioning formula for short flows- M/G/R-PS extension for multiple rpeak- consideration of QoS mechanisms and multiple QoS levels

• network dimensioning algorithm (similar to the well-known unified algorithm for PSTN and ATM networks) with following features:- integrated (IGP) routing optimization- consideration of constraints imposed by TE and QoS mechanisms like MPLS, OMP, DiffServ- multiple load period dimensioning - point-to-any dimensioning (for DiffServ networks)- consideration of restoration capabilities (e.g. via MPLS)- dimensioning for multiple QoS metrics

• integration of dimensioning algorithm and TE system in automated planning and engineering system

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IP Traffic Engineering IP Traffic Engineering and QoS Provisioningand QoS Provisioning

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IP Traffic Engineering and QoS Provisioning

• State-of-the-art:• separate application of Traffic Engineering and QoS

mechanisms (multipath routing (OMP), MPLS LSP adaption, DiffServ, IntServ) in IP networks

• Challenges:• performance evaluation of TE / QoS mechanisms• use of TE for fast load adaption and restoration• development of optimum TE control algorithm (objectives/constraints of TE?)• information exchange/interaction of TE mechanism and routing• combination of different mechanisms: MPLS-OMP, MPLS-DS

- requires protocol enhancements > new IETF drafts- driver: search for optimum tradeoff between overprovisioning and complexity- strong relationship to SLA formulation- will admission control be really neccessary?

• end-to-end QoS provisioning: reasonable scenarios MPLS TE MultipathRouting (OMP)

DiffServ

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Further important Further important Engineering IssuesEngineering Issues

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Further important Engineering Issues

• Optimization tasks concerning routing protocols:• IGP (OSPF, ISIS) design / optimization rules• EGP (BGP-4) design / optimization rules (e.g. application and #

of route reflectors, confederations etc.)• traffic induced by routing protocol• performance evaluation of routing protocols

• Optimization of Data Center (server site) locations• Engineering of Data Centers

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Special Topic: Special Topic: MPLS-DiffServ* MPLS-DiffServ*

*partially taken from MPLS2000 Conference material

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MPLS-DiffServ

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MPLS-DiffServ

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MPLS-DiffServ

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MPLS DiffServ (DS)

DS over MPLS(or: MPLS - DS):•E-LSP•L-LSP•TE not CoS aware!

DS aware MPLS TE:•TE is CoS aware

OMP

MPLS-OMP

DS aware MPLS TE + RSVP CAC for rt-Traffic (e.g. voice)

reinvention of ATM!

IntServ

increasing complexity!

MPLS-DiffServOverview

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DS over MPLS: • “MPLS Support of Diff-Serv”draft-ietf-mpls-diff-ext-07.txt, Aug 2000

MPLS TE: • “Requirements for Traffic Engineering Over MPLS”RFC2702, Informational RFC

• “RSVP-TE: Extensions to RSVP for LSP Tunnels”draft-ietf-mpls-rsvp-lsp-tunnel-07.txt, Aug 2000

• “Constraint-Based LSP Setup using LDP”draft-ietf-mpls-cr-ldp-04.txt, Jul 2000

• “Extensions to ISIS for TE”draft-ietf-isis-traffic-03.txt, Sept 2000

• “TE extensions to OSPF”draft-katz-yeung-ospf-traffic-03.txt, Oct 2000

DS aware MPLS TE: • “Requirements for support of Diff-Serv-aware MPLS Traffic Engineering”draft-lefaucheur-diff-te-reqts-00.txt, Jul 2000

• “Extensions to IS-IS, OSPF, RSVP and CR-LDP for support of Diff-Serv-aware MPLS TE”draft-lefaucheur-diff-te-ext-00.txt, Jul 2000

MPLS-DiffServIETF Drafts

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MPLS-DiffServExample: MPLS TE

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MPLS-DiffServExample: DS over MPLS

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MPLS-DiffServExample: DS aware MPLS TE

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MPLS-DiffServExample: DS aware MPLS TE

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MPLS-DiffServExample: VoMPLS - DS aware MPLS TE with RSVP CAC

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“ultimate QoS” solution for VoMPLS:QoS never degradesautomatic/dynamic traffic engineering of voice

(exceeds today’s TDM TE capabilities)excess calls get rejected if/when EF-capacity exceededtraffic patterns do not have to be known beforeThis level of sophistication is only useful in some environmentsUnder construction at IETF

MPLS-DiffServVoMPLS: DS aware MPLS TE with RSVP CAC

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MPLS-DiffServ

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Additional Additional SlidesSlides

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MPLS-DiffServIP VPN-Concepts: HOSE Model

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MPLS-DiffServIP VPN Concepts: PIPE Model

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Current IGP extensions for TE:advertise “unreserved TE bandwidth” (at each preemption level)Proposed IGP extensions for DS aware TE:Class-Types= group of Diff-Serv classes sharing the same bandwidth

constraint (eg AF1x and AF2x)advertise “unreserved TE bandwidth” (at each preemption level) for each

Class-TypeCurrent LSP-signalling extensions for TE:at LSP establishment signal TE tunnel parameters (label, explicit route,

affinity , preemption,…)Proposed LSP-signalling extensions for DS aware TE:also signal the Class-Typeperform Class-Type aware CAC

Current Constraint Based Routing for TE:compute a path such that on every link there is sufficient “unreserved TE

bandwidth”Proposed Constraint Based Routing for DS aware TE:same CBR algorithm but satisfy bandwidth constraint over the “unreserved

bandwidth for the relevant Class-Type” (instead of aggregate TE bandwidth)

MPLS-DiffServNecessary Enhancements for DS aware MPLS TE

Documents

Senior Consultant Network Planning and Design Siemens AG, München