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T. Bauschert 11.05.2001 1IP Network Engineering Challenges
Senior ConsultantNetwork Planning and DesignSiemens AG, München
Email: thomas.bauschert@icn.siemens.de
Dr. Thomas Bauschert
IP Network Engineering ChallengesIP Network Engineering Challenges
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T. Bauschert 11.05.2001 2IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 3IP Network Engineering Challenges
Network ArchitectureNetwork Architecture
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T. Bauschert 11.05.2001 4IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 5IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 6IP Network Engineering Challenges
IP Traffic SpecificationIP Traffic Specification
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T. Bauschert 11.05.2001 7IP Network Engineering Challenges
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 Parameter
QoS 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 relationshipto QoS mechanisms
UserSite
ServerSite
ISPs /Internet
1)
2)
3)
4)
5)6)
Cache
IP Network
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T. Bauschert 11.05.2001 8IP Network Engineering Challenges
IP Network DimensioningIP Network Dimensioning
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T. Bauschert 11.05.2001 9IP Network Engineering Challenges
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
R
RRE
r
xxTE
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
d
C
d
ME
M
CB
Cr
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 e
t o t a l o f f e r e dt 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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T. Bauschert 11.05.2001 10IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 11IP Network Engineering Challenges
IP Traffic Engineering IP Traffic Engineering and QoS Provisioningand QoS Provisioning
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T. Bauschert 11.05.2001 12IP Network Engineering Challenges
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 TEMultipath
Routing (OMP)
DiffServ
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T. Bauschert 11.05.2001 13IP Network Engineering Challenges
Further important Further important Engineering IssuesEngineering Issues
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T. Bauschert 11.05.2001 14IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 15IP Network Engineering Challenges
Special Topic: Special Topic: MPLS-DiffServ* MPLS-DiffServ*
*partially taken from MPLS2000 Conference material
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T. Bauschert 11.05.2001 16IP Network Engineering Challenges
MPLS-DiffServ
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T. Bauschert 11.05.2001 17IP Network Engineering Challenges
MPLS-DiffServ
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T. Bauschert 11.05.2001 18IP Network Engineering Challenges
MPLS-DiffServ
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T. Bauschert 11.05.2001 19IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 20IP Network Engineering Challenges
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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T. Bauschert 11.05.2001 21IP Network Engineering Challenges
MPLS-DiffServExample: MPLS TE
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T. Bauschert 11.05.2001 22IP Network Engineering Challenges
MPLS-DiffServExample: DS over MPLS
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T. Bauschert 11.05.2001 23IP Network Engineering Challenges
MPLS-DiffServExample: DS aware MPLS TE
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T. Bauschert 11.05.2001 24IP Network Engineering Challenges
MPLS-DiffServExample: DS aware MPLS TE
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T. Bauschert 11.05.2001 25IP Network Engineering Challenges
MPLS-DiffServExample: VoMPLS - DS aware MPLS TE with RSVP CAC
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T. Bauschert 11.05.2001 26IP Network Engineering Challenges
“ultimate QoS” solution for VoMPLS:
QoS never degrades
automatic/dynamic traffic engineering of voice
(exceeds today’s TDM TE capabilities)
excess calls get rejected if/when EF-capacity exceeded
traffic patterns do not have to be known before
This level of sophistication is only useful in some
environments
Under construction at IETF
MPLS-DiffServVoMPLS: DS aware MPLS TE with RSVP CAC
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T. Bauschert 11.05.2001 27IP Network Engineering Challenges
MPLS-DiffServ
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T. Bauschert 11.05.2001 28IP Network Engineering Challenges
Additional Additional SlidesSlides
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T. Bauschert 11.05.2001 29IP Network Engineering Challenges
MPLS-DiffServIP VPN-Concepts: HOSE Model
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T. Bauschert 11.05.2001 30IP Network Engineering Challenges
MPLS-DiffServIP VPN Concepts: PIPE Model
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T. Bauschert 11.05.2001 31IP Network Engineering Challenges
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
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