전달망에서의 QoS & Traffic Engineering 기술 2006.2.23 이순석 (sslee@etri.re.kr) BcN 설계팀광대역통합망연구단
목차 QoS 필요성에대한논쟁 인터넷의 QoS 문제 IP QoS 기술동향 QoS Routing DiffServ MPLS TE DiffServ over MPLS DS-aware TE BcN 에서의 QoS & TE BcN TE Flow based QoS Flow-based TE Interworking 토의 부록 1
Bandwidth Booster 의시각 QoS 의장점 Bandwidth Booster 들의반론 도로같은경우는건설비용이엄청비싸다. 트래픽이항상 QoS를필요로하는수준까지차는것은아니다. 응급상황이란것은극히미미한수준이다. 트래픽의증가속도가미미하다면, QoS는가치가있다 트래픽증가속도가빠르기때문에, Bandwidth 로해결하는것이최선? 2
Class Warrior 의시각 Class Warrior 의반론 종단간의적어도하나의링크가거의항상 bottleneck이다. 특히, access 구간이심하다 백본도예외일수없다. Oversubscription! Synchronization! End-to-end communication High peak 트래픽에대한대책이없다 시장에서품질을요구한다. 예 ) VPN 설문조사 : CoS/QoS 가필요없다 4% Ref.) Light Leading, IP Quality of Service- The End of Packet Democracy 3
인터넷의 QoS 문제
P1. 분산제어방식에따른제어성과신뢰성이부족하다 Guarantee of Real-time controllability Slow Network Convergence (example: IS-IS converging time) Routing loop, black hole routes, suboptimal routes Additional Delay for generation Delay for flooding Initial waiting time (5.5 sec) No flooding SPF computation time If larger than 5 sec, LSP retransmitted from neighbors RIB/FIB updating time Partial Route Calculation - Initial waiting time : 2 sec - Interval for PRC : 5 sec LSP generation & flooding - Transmission interval : 33 ms Min. interval of LSP (5 sec) LSP receives from neighbors Event occurs -Adjacency flap -Interface flap -Change in i/f metric -Change in inter-area routes -Change in redistributed (external) routes Interval for consecutive SPF processing (10 sec) SPF Starts Ack (PSNP) Time-gap! RIB updates Completion of RIB/FIB updating 5
P2. 네트워크자원사용에대한수락제어기능이없다 CAC 기능만있으면되는가? Video server A Resource Mediator (QoS Manager, Bandwidth Broker) Video client A 50M AF 100 Mbit/s AF 100 Mbit/s AF 100 Mbit/s AF 100 Mbit/s Video client B Video server B AF 100 Mbit/s Diffserv Diffserv network network AF 10 Mbit/s Video client C 50M 서비스불가 10M Server B -> Client B : 50M 6
P3. 라우터에품질제공메커니즘이부족하다 Per-class Policing + RED/WRED Router Per Path, Per Class Bandwidth Traffic Class QoS Profile ACL Meter Per Class Queue Per Path Queue Incoming Packets L2/L3 Classifier Marker Per Class Shaper Policer MAX RED/ WRED MIN Outgoing Packets VLAN LIB FIB 7
P4. 인터넷은공평하지못하다 정보화지수가높은지역 가입자 Planning? Reference User? 원거리통신상대적불리 Fast retransmit and recovery Congestion Window 8 4 2 1 Slow start Congestion avoidance 2 W W+1 W RTT RTT RTT Time 8
P5. 인터넷은패킷만을인식한다 ONLY packet-by-packet processing Per-session control. Impossible!! 9
IP QoS 기술동향
IETF 의 IP QoS 역사 30 여년간의지속적인요구사항수정 Complexity 보이지않는또하나의시장장벽 Source: Cisco, Advanced Concepts and Developments in MPLS 11
QoS Routing Constraint based Routing Multiple Constraints Complexity Non-linearity Size of memory 생각해볼수있는대안 시간종속적 link-cost <- Traffic Analysis 트래픽종속적 link-cost -> Instability 유발 Routing Performance 향상을위한접근 링크상태갱신 주기적갱신방법 임계값기반갱신방법 안정성기반 트래픽증감율 갱신빈도 12
DiffServ (1999) How many # of classes or queues are enough? Survey 3~ 4 classes : 75% More than 4 : 25% Class Assured Forwarding 4 traffic classes x 3 drop precedences Expedited Forwarding VLL : low latency/jitter/loss, B/W Best effort Question? How to guarantee e2e B/W? reservation, pinning 13
Tips IP Multicasting 접근방법론의모순 Big-Pipe 입장에서보면 Broadcasting 으로충분 왜, Multicast Packet 전달을위한 protocol 이별도로필요한가? User 가있는곳에만 packet 을보낸다? Topology dynamics? Dynamics 를제거하려면? 특별한class와이class에대한bandwidth limit 지정필요! 다른서비스 class가사용못함 이것은사업자입장에서 program channel을선택하는것과동일! 14
DiffServ over MPLS Link-by-link full search 방식의확장성문제 Cut-through 입구에서의제어 Cut-through 단위의트래픽제어를하지않음 Link-by-link full search 필요 15
DS-aware TE (DS-TE) 기본발상 Class 별사용률지정 Class 단위 cut-through Class 별 CAC Per-class B/W pool Class 별 booking ratio 조절 utilization 조절 Low-priority class 의 queue 는상대적으로커야함 No modification for Data Plane Per-class FIFO Transfer Performance 의 upper-bound 제공가능? Dynamics 증가 Unreserved b/w per-class unreserved b/w 16
MPLS 의 Reliability RSVP-TE Refresh Reduction Continuity check? No return path No OAM for UNI No Return Path Guaranteed MPLS Ping? Fast Re-Routing Local restoration Why FRR needs? Slow restoration of Path Protection? Expert Operator? Protection VSP (pre-provisioned) Working VSP CE CE optical propagation delay=2ms (500km) FDI (3x3ms) FDI insertion (3ms) processing time=19ms BDI detection (3x3ms) optical propagation delay=2ms (500km) BDI insertion (3ms) processing time=19ms switch over working to protection VSP 17
Business Model 관점에서의 IP QoS 서비스의발전은인터넷을변하게하였다 End-to-end Argument model 의종말, 왜? 단말만으로는불가능 Dumb Network Flexibility Generality Openness 새로운요구사항 = 돈 을만들수있게해달라 萬人一色 에서 一人十色 서비스가가능하도록해달라 맞춤품질 : Per-session, Per-VPN, Per-session in VPN, 이동성 보안성 SLA Billing 18
IntServ 는불가능한가? 왜 IntServ 는부적절하다고하나? IntServ RSVP Data Packet Routing Protocol Daemon RSVP Daemon Per-flow State flow 1 MF flow 2 Classifier Admission Controller Sched. RSVP Per-flow state Routing Protocol Process RSVP Process Per-flow State flow 1 MF flow 2 Classifier Admission Controller Sched. RSVP Routing Protocol Process RSVP Process Per-flow State flow 1 MF flow 2 Classifier Admission Controller Sched. flow n flow n flow n Ref.) NetManias 다른방법은없는가? 19
BcN 에서의 QoS & TE
BcN 요구사항 QoS& TE 관점 서비스측면 서비스에따른맞춤품질 품질제공수준에따른과금 GoS QoS Usage End-to-end 이동성지원 Best-effort 도최소한현재수준은보장? OpEx 관점 Network Load balancing Resource optimization Minimization of communication Cost Aggregation/Segregation Reducing Complexity Guaranteeing Best Network Performance 21
Scope of TE IETF TEWG Load Uncertainties Network Forecast Traffic Load Actual Traffic Traffic Data Capacity Changes Routing Table Update Controls Seconds - Minutes Days - Weeks Months - Years Node/Link Sizes (Traffic & Transport) Routing Tables (Traffic & Transport) Traffic Engineering Functions Traffic Management (Bandwidth Broker, Routing Policy) Capacity Management (Routing Design, Capacity Design) Network Planning (Node Planning, Transport Planning) 22
Open Problems BcN TE Do NOT know the reference user of BcN Service Exception for VoIP Network Dimensioning Service 의트래픽특성? Off-line simulation Service 의호특성? BHCA, Erlang How to analyze the network level behaviors? Per-class, Per-service From/To Matrix QoS monitoring per class, per service Trial & Error approach based on Internet, PSTN, CDMA, mobile Internet,.. 23
So, we need ITS+ in communication! TMN 의태초의꿈을실현시켜야할때 항목 NMS/EMS ( 상용시스템 ) NCP 기본성격 기능 망장비의물리적구성관리를기반으로망장비레벨의수동적상태감시기능을담당하는중앙감시시스템 망장비의물리적구성관리 노드및링크레벨상태감시 링크단위의성능감시 물리적장애감시 NMS 접근제한기반의보안기능 망장비단위의상태정보를바탕으로네트워크레벨상태정보로가공하여서비스제공에필요한망장비의실시간제어기능을담당하는중앙제어시스템 NMS/EMS 네트워크레벨의자원사용현황추출 e2e 망자원수락제어 서비스및네트워크레벨의정책제어 경로시뮬레이션및경로최적화등의자원사용최적화 장애및신규자원요청에대한시뮬레이션을통한영향도예측 e2e 서비스 Provisioning e2e 성능관리및서비스품질관리 실시간자원감시기반의망접속제어 Per-Session 단위과금정보추출 비고 e2e 서비스관리를위해서는막대한추가비용필요 QoS, 가용도, 보안, SLA 등의종합서비스품질을지향하는 BcN 서비스제공을위한필수중앙제어시스템 교통흐름을단순히감시하는 CCTV 교통흐름을실시간으로제어하는 ITS+ 24
BcN QoS
Flow based QoS Flow? IP 헤더의의미있는정보들의조합으로만들수있는모든群 Cf.) IETF flow = (src prefix, dst prefix) IETF flow 의용도 Traffic Engineering F/T matrix Netflow, sflow DS-TE, BcN 에서도가능? 성능문제발생 가격? BcN QoS = f (Rate, Loss, delay, Jitter, Availability) Per-session 26
PHB of Flow-based QoS Flow vs. Packet Flow 기반 QoS 개별서비스단위로실시간패킷群인식 분류기준 : 3-tuple, 5-tuple, 6-tuple 개별서비스단위로 policing 가능 (QoS profile 적용시 ) Malicious traffic 자동적으로 policing 개별서비스단위로 implicit admission control 가능 개별서비스단위 drop precedence 적용가능 동일서비스群에속한개별서비스들에대한 fairness 보장가능 Transfer Capability : MR, GR, CR, AR Packet 기반 QoS ( 상용라우터 ) DiffServ : 서비스군별 Policing Malicious traffic 존재시, 무작위 drop QoS 보장불가 개별서비스단위제어를위해서는 ACL 제어필요 대용량 ACL Lists 필요 27
Flow-based TE Flow-based TE Scalable IntServ PHB of Flow based QoS SMPLS TE Aggregation B/W guaranteed LSP Opaque mode Transparent mode OAM based FM, PM, Protection/Restoration Usage & QoS Monitoring per Premium flow Network Policy Management SLA Management SLS Analysis Call Statistics Resource Manager VSP Planner Network Monitoring Flow-based PHB (Per Hop Behavior) Node monitoring Flow-based Traffic Control Policy-based Flow-to-VSP Mapping Path monitoring Virtual Switched Path Network Over Real-time Traffic Engineering Policy-based Flow-to-VSP Mapping Node monitoring Flow-based Traffic Control Flow-based PHB OAM per VSP(LSP) PM per Sampled flow per class 28
Scalable IntServ No Bearer Signaling Without SIP Future Feature Gate Control for Network Security Call Agent Scalable IntServ Admission control SIP Policy control NCP Pre-provisioning Data Packet RPD MF Classifier Per-microflow State uflow 1 uflow 2 Sched. RPD MF Classifier Per-flow State flow 1 flow 2 Sched. RPD MF Classifier Per-microflow State uflow 1 uflow 2 Sched. uflow n * RPD : Routing Protocol Daemon flow m uflow n 29
2 types of VSP Opaque mode B/W guaranteed Pipe 서비스 하나의 VSP에 Multiple class flow 수용가능 WFQ per VSP at each PHB 용도 Network Load balancing Hard Secure L2VPN 서비스에활용가능 Transparent mode B/W guaranteed Pipe 서비스 하나의 Pipe 내에서 DiffServ 제공가능 하나의 VSP에 Multiple class flow 수용가능 30
Legacy Router vs. QSS 분류단위 QoS LSP L/L-like Legacy Router QSS PE Core, Core Edge Edge Core 패킷단위 Flow 단위분류시, 실시간 ACL 필요 CoS Flow Classification Flow Policing Flow Queueing Flow Scheduling Flow Shaping CoS Flow Classification Flow Policing Class Queueing Class Scheduling Flow Shaping E-LSP -FTN per Service type -Packet-by-Packet PHB (DiffServ) Over-provisioning at Core Session 단위분류가능 자동 (6-tuple) Automatic μflow classification μflow/flow Policing μflow/flow Queueing μflow/flow Scheduling μflow/flow Shaping Connection Admission Control for guaranteed class CoS (option) ADP (option) Opaque mode LSP (OM-LSP) No Over-provisioning QoS profile for each label (Edge) QoS Profile for OM-LSP (Core) L3 MPLS for Traffic Engineering 용 L/L-like VPN 용 (VLAN.id 기반 ) AGW-to-AGW Pipe 용 (VLAN.id 기반 ) Tunnel L-LSP (IETF) -FTN per Service type -Per LSP QoS (No QoS per μflow) -Rate Limiting in LSP Over-provisioning at Core VoIP, MMoIP, VoD, Conference Call, 31 Transparent mode LSP (TM-LSP) - FTN per Service type - Per μflow QoS (DSCP/EXP based QoS Profile) - Connection Admission Control in LSP - Shaping for LSP (Limits for # of LSP per LC=64) VoIP, MMoIP, VoD, Conference Call,
Interworking w/ Legacy Inter-Subnet 간연동 Access network BcN Backbone DSCP remarking Pre-determined QoS Profile for each DSCP Flow class Application characteristics Corresponding DSCP name & value MR GR CR AR control traffic jitter sensitive, real-time, interactive non-rt but loss sensitive peak rate Interactive or transaction, minimum rate BE, available rate DiffServ as Edge node of Fb-TE This is NOT Flow-based TE! CS7, CS6 111000, 110000 EF, CS5, AF4x 101010, 101000, 100010,100100,100110 AF3x, CS4, AF2x, CS3 011010,011100,011110,100000 010010,010100,010110,011000 AF1x, CS2, CS1, DF(CS0) 001010,001100,001110, 010000, 001000,000000 32
DiffServ as Core node of Fb-TE Pre-provisioning for Legacy Over-Provisioning by CLI Policing at ingress Shaping at Egress DSCP mapping Static Cross-connect CAC, per Flow Shaping LSP QSS QSS Guaranteed IP Connectivity - Over-Provisioning Guaranteed Path/VPN -L2 VPN 33
토의 IP 30 년역사는우리가넘을수없는견고한벽! 시장 Routing Protocol의복잡도 NP 기술 그러나 NGN 시대에는 Seamless 서비스 통방융합서비스 우리것을만들되, 범세계적인 Standard 가되어야함 CDMA, 반도체, WiBro. 모두가새로운패러다임을추구한것 34
감사합니다.
부록
광대역통합망구조개관 현재의통신망 BcN 통합망 망관리서비스제어액세스 NMS NMS NMS NMS AAA AAA AAA AAA 응용 응용 응용 응용 콜서버 IPTV NGN VoIP CDMA CATV AG 일반전화인터넷 2G/3G CATV Unpredictable IP Network All-IP Mobile Multimedia Controller Platform PSTN Open API 응용 AG Open API GW 인터넷 VoIP CATV 웹응용 서비스관리 WLAN 2G/3G SIP 응용 Network Control Platform Managed IP Network Seamless Converged Access Network FTTH WiBro 통합 AAA Manageable All IP Network 4G U-Access 서비스단위의복수망 : 투자비및유지비증가 인터넷의속도기반경쟁으로투자비지속증가 새로운 Business Model 창출에한계 - 가입자포화 - 인터넷기반콘텐츠무한경쟁 - 十人一色 서비스로인한가입자차별화불가 37 단일통합망기반의투자비및유지비최소화 액세스 / 서비스기술고도화에투자집중가능 통 / 융합기반의새로운 BM 창출용이 - Portable Internet Mobile Multimedia - 맞춤품질기반합리적비용모델제공가능 - 一人十色 의다양한서비스모델제공
네트워크진화요인 PSTN/ 이동통신망 CATV/ 방송 유무선인터넷 BSC LEX MSC Tandem Tandem Toll/IGS Toll/IGS - 대규모망을위한메트로망존재 - End-to-end communication 서비스모델 - End-to-end QoS 보장 - Narrowband, 서비스종류의단순 - 세션이동성제공 - Call 기반 business model CM HFC CMTS 방송용전송망 - 통방통합용이 - End-to-end QoS - Broadband PP DSLAM/ L2 SW BSC/ RNC ER PDSN/ SGSN CR GGSN - 메트로망이존재하지않음 - Client-Server 서비스모델 - Best effort/diffserv 기반 CoS 품질 - Broadband - 보안취약 - 가입자기반 business model 유무선 / 방송통합 All IP 38
네트워크진화방향 가입자인증 서비스인식 서비스접근인증 서비스별 QoS IPTV Zapping L2/L3 핸드오버 L2 VPN 서비스 RGW L2 SW FTTH/ ME SW A-NCP ASR 10 QSR 80 M-NCP QSS 120 서비스제어플랫폼 QSR 240 B-NCP BCR 실시간통합자원관리 세션이동성제어지원 대규모 IPCasting 제어 IX/TGW 인터넷 /PSTN Legacy Access 유무선통합액세스? QoS Re-mapping ( Legacy) μflow 별 QoS 및품질모니터링 Local 라우팅 /MPLS 스위칭 트래픽 Aggregation IPTV stream 분배 L3 핸드오버지원 L2/L3 VPN 지원 L3 핸드오버지원 Macro-Flow 별 QoS QoS 라우팅 MPLS 스위칭 L2/L3 VPN 지원 OXC 연동 39
BcN End-to-end QoS Solution CASS SCP: Service Control Point SER: Service Edge Router SGSN/AR : Serving GPRS Support Node/Access Router SGW : Signaling Gateway TE : Traffic Engineering TGW : Trunk Gateway WGW: Wireless Gateway IMS: IP Multimedia Subsystem RM: Resource Manager OLT: Optical Line Termination ACR : Access Control Router AGW: Access Gateway RAS : Remote Access Server B-NCP : Backbone NCP BSC : Base Station Controller BSS : Business Service System BTS : Base Transceiver System ER: Edge Router EMS : Element Management GGSN : Gateway GPRS Support Node HA : Home Agent M-NCP : Metro NCP PDGN:Packet Data Gateway Node PDSN:Packet Data Support Node Prov. Server : Provisioning Server A-NCP PS RM CASS M-NCP Prov. Server RM Call Server Prov. Server B-NCP RM Call Server M-NCP Prov. Server SGW RM SCP SS7 Network PSTN Network CASS TGW AP RAS DSLAM Broadband Access Network Node B ASR10 RNC QSR20/80 CDMA2000 1x BTS Bearer BSC/PCF ACR(FA) AGW Packet QSS120 QSS120 Metro Network OXC SGSN/AR PDSN/FA WGW AAAF/H HA GGSN PDGN QSS120 QSR240 SER OXC ER 40 BcN Core Network Internet OXC-PS Other ISP Internet QSR240 OXC SER Metro Network QSS120 QSS120 OXC PON 기반통합액세스 RG/STB/HGW OLT QSS120 HFC/CATV A-NCP PS RM CMTS CM/Set-top