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s IP Network Engineering Challenges Dr. Thomas Bauschert Senior Consultant Network Planning and Design Siemens AG, München Email: [email protected] IP Network Engineering Challenges T. Bauschert 11.05.2001 1 s 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 IP Network Engineering Challenges T. Bauschert 11.05.2001 2 s Network Architecture IP Network Engineering Challenges T. Bauschert 11.05.2001 3 s Network Architecture • State-of-the-art network architecture: • switched (MPLS) IP core network (highly meshed) • multiple homed distribution/access routers Internet Exchange Interconnect Router Partially meshed STM-64 / 160 GigaEth Core Router(320G) Ring STM-16/64 / 32 * Distribution Router(40G) Data Center Router Ring STM-4, GigaEth / 32 * Access Router Aggr. Devices Data Centers STM-1/4, GigaEth STM-1 Access Devices GigaEth MGW 100bT E1, E3, STM-1 LL Local Exchange IP Network Engineering Challenges T. Bauschert 11.05.2001 4 s 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) state-of-the-art future ASON ATM virtual meshing via ATM PVCs physical meshing virtual meshing via wavelenghts router throughput < 1 Gbit/s, STM-16 I/F router throughput < 1 Tbit/s, STM-64 I/F router throughput < 1 Tbit/s n x STM-64 DWDM I/F IP Network Engineering Challenges T. Bauschert 11.05.2001 5 s IP Traffic Specification IP Network Engineering Challenges T. Bauschert 11.05.2001 6 s 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 Traffic Class 1 Traffic Class 2 Stream Traffic QoS 1 • • • • • • WWW FTP Traffic Class 3 Stream Traffic QoS 2 Elastic Traffic QoS 1 • arrival rate + duration or: offered traffic mean + peak bitrate blocking probability connection setup delay packet delay / jitter / loss • • • • • ... Services/ Applications ... Traffic Classes Elastic Traffic QoS 2 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 IP Traffic Types (w/w.o. QoS guarantee) Traffic Parameter QoS Param. (flow) QoS Param. (packet) Server Site 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 IP Network Engineering Challenges 5) 6) 1) User Site ISPs / Internet 4) IP Network Cache 3) strong relationship to QoS mechanisms T. Bauschert 11.05.2001 7 s IP Network Dimensioning IP Network Engineering Challenges T. Bauschert 11.05.2001 8 s 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 average time to transfer a file of length x file length E{T ( x)} ratio C / rpeak x E 2 ( R, R ) 1 rpeak R(1 ) utilization: = (·xmean)/C peak bit rate blocking blocking probability probabilityofof traffic trafficclass classss solution solutionofofthe the characteristic characteristic polynom polynom effective effectivebitrate bitrate ofoftraffic trafficclass classss service discrimination (realized by link buffer scheduler) average TCP throughput offered elastic traffic volume elastic traffic offered stream traffic stream traffic blocked stream traffic carried stream traffic admission control Bs 1 rs ( C ) M C E1 , C d d 1 M bitrate bitrateofofthe the equivalent equivalentsingle single server serversystem system total totaloffered offered traffic trafficvolume volume link capacity IP Network Engineering Challenges T. Bauschert 11.05.2001 9 s 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 IP Network Engineering Challenges T. Bauschert 11.05.2001 10 s IP Traffic Engineering and QoS Provisioning IP Network Engineering Challenges T. Bauschert 11.05.2001 11 s 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 IP Network Engineering Challenges Multipath Routing (OMP) MPLS TE DiffServ T. Bauschert 11.05.2001 12 s Further important Engineering Issues IP Network Engineering Challenges T. Bauschert 11.05.2001 13 s 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 IP Network Engineering Challenges T. Bauschert 11.05.2001 14 s Special Topic: MPLS-DiffServ* *partially taken from MPLS2000 Conference material IP Network Engineering Challenges T. Bauschert 11.05.2001 15 s MPLS-DiffServ IP Network Engineering Challenges T. Bauschert 11.05.2001 16 s MPLS-DiffServ IP Network Engineering Challenges T. Bauschert 11.05.2001 17 s MPLS-DiffServ IP Network Engineering Challenges T. Bauschert 11.05.2001 18 s MPLS-DiffServ Overview OMP MPLS-OMP increasing complexity! MPLS DiffServ (DS) IntServ DS over MPLS (or: MPLS - DS): •E-LSP •L-LSP •TE not CoS aware! DS aware MPLS TE: •TE is CoS aware DS aware MPLS TE + RSVP CAC for rt-Traffic (e.g. voice) IP Network Engineering Challenges reinvention of ATM! T. Bauschert 11.05.2001 19 s MPLS-DiffServ IETF Drafts 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 over MPLS: • “MPLS Support of Diff-Serv” draft-ietf-mpls-diff-ext-07.txt, Aug 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 IP Network Engineering Challenges T. Bauschert 11.05.2001 20 s MPLS-DiffServ Example: MPLS TE IP Network Engineering Challenges T. Bauschert 11.05.2001 21 s MPLS-DiffServ Example: DS over MPLS IP Network Engineering Challenges T. Bauschert 11.05.2001 22 s MPLS-DiffServ Example: DS aware MPLS TE IP Network Engineering Challenges T. Bauschert 11.05.2001 23 s MPLS-DiffServ Example: DS aware MPLS TE IP Network Engineering Challenges T. Bauschert 11.05.2001 24 s MPLS-DiffServ Example: VoMPLS - DS aware MPLS TE with RSVP CAC IP Network Engineering Challenges T. Bauschert 11.05.2001 25 s MPLS-DiffServ VoMPLS: DS aware MPLS TE with RSVP CAC n “ultimate QoS” solution for VoMPLS: n QoS never degrades n automatic/dynamic traffic engineering of voice (exceeds today’s TDM TE capabilities) n excess calls get rejected if/when EF-capacity exceeded n traffic patterns do not have to be known before n This level of sophistication is only useful in some environments n Under construction at IETF IP Network Engineering Challenges T. Bauschert 11.05.2001 26 s MPLS-DiffServ IP Network Engineering Challenges T. Bauschert 11.05.2001 27 s Additional Slides IP Network Engineering Challenges T. Bauschert 11.05.2001 28 s MPLS-DiffServ IP VPN-Concepts: HOSE Model IP Network Engineering Challenges T. Bauschert 11.05.2001 29 s MPLS-DiffServ IP VPN Concepts: PIPE Model IP Network Engineering Challenges T. Bauschert 11.05.2001 30 s MPLS-DiffServ Necessary Enhancements for DS aware MPLS TE Current IGP extensions for TE: n advertise “unreserved TE bandwidth” (at each preemption level) Proposed IGP extensions for DS aware TE: n Class-Types= group of Diff-Serv classes sharing the same bandwidth constraint (eg AF1x and AF2x) n advertise “unreserved TE bandwidth” (at each preemption level) for each Class-Type Current LSP-signalling extensions for TE: n at LSP establishment signal TE tunnel parameters (label, explicit route, affinity , preemption,…) Proposed LSP-signalling extensions for DS aware TE: n also signal the Class-Type n perform Class-Type aware CAC Current Constraint Based Routing for TE: n compute a path such that on every link there is sufficient “unreserved TE bandwidth” Proposed Constraint Based Routing for DS aware TE: n same CBR algorithm but satisfy bandwidth constraint over the “unreserved bandwidth for the relevant Class-Type” (instead of aggregate TE bandwidth) IP Network Engineering Challenges T. Bauschert 11.05.2001 31