Scalability Analysis Of L2 And L3 VPN Technologies Service .

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Scalability Analysis of L2 and L3 VPN TechnologiesService Provider PerspectiveAlex ZININCTO IPD APAC, Alcatel-LucentAll Rights Reserved Alcatel-Lucent 2006, #####

What is Scalability Analysis?Different approaches have different complexity (overhead) Computational (CPU utilization) Data (amount of state) Signaling (required BW) Management & provisioning (OPEX)Goal of scalability analysis: Understand growth of overhead as complexity input parameters increaseMethod--asymptotic complexity analysis Asymptotic behavior of f(n) growth of f(n) as n gets larger Typically ignore small values of n Slower asymptotic growth – better O-notation for “order” of growth, e.g.:f(n) n2 25*n - 10 O(n2)f(n) 100*n22 MPLS Japan 2007 Oct 10, 2007 O(n2)All Rights Reserved Alcatel-Lucent 2007

f1()Example: CPU overhead functions)f2(f1() )f2(Compare overhead functionsfor two algorithms f1() and f2()3 MPLS Japan 2007 Oct 10, 2007Both appear linearf2() better than f1()All Rights Reserved Alcatel-Lucent 2007

Example: CPU overhead functionsO (Lf1() og x))f2((x O)On a different scalef1() better than f2()4 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Example: CPU overhead functionsOSPFRIPNumber of linksChoice of better solutiondepends on problem scope5 MPLS Japan 2007 Oct 10, 2007BUTGenerally inferior solutioncan be better for small problemsAll Rights Reserved Alcatel-Lucent 2007

Network Protocol Scaling AnalysisControl Plane Number of protocol sessions (adjacencies, TCP connections, etc.) Amount of state (LSAs, routes, etc.) Computational overhead (CPU load) Signaling overhead (required BW)Data Plane Amount of state (routes, MAC addresses, etc.) Computational overhead (forwarding, flooding, replication, etc.)Management Plane Provisioning overhead Troubleshooting complexity6 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Reason for Scaling AnalysisUnderstand technology aspects Maximum number of nodes, users, services Potential bottlenecks Sensitive implementation areasUnderstand cost functions Cost of initial deployment Cost growth curve as function of number of subs/svcsMemMem)O(x)gxLoog x)((LOO# subs#(exp)subs7 MPLS Japan 2007 Oct 10, 2007# subs#(exp)subsAll Rights Reserved Alcatel-Lucent 2007

VPN Scaling Analysis—General AspectsWhat is the scaling factor? Number of CPE devices? Number of end users?CPECPECPESPNetworkCPEL2VPNs: sites MAC addressesCPEL3VPNs: sites IP routes8 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

VPN Scaling ParametersL2 VPNs: Control PlaneL3 VPNs: Control Plane Sessions: T-LDP Sessions: iBGP State: PWs, MAC addresses State: VPN Routes CPU: LDP, MAC table CPU: BGP, PE-CE Signaling: PW setup, status,MAC withdraw Signaling: route updates,withdrawL2 VPNs: Data PlaneL3VPNs: Data Place State: MAC table State: VPN Routes Computation: MAC lookup,flooding, mcast replication CPU: FIB lookup, mcastreplication9 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Basic ConfigurationL3 VPNs: basic MPLS/BGPL2 VPNs: flat VPLS Full mesh T-LDP Full mesh iBGP No multicast optimizations No multicast optimizationsPEPEPEPEPLDTPEPEPES: number of sitesN: number of PE nodes O(Log S)M: number of MAC addressesV: number of VPN instances10 MPLS Japan 2007 Oct 10, 2007GPiBPEPEPES: number of sitesN: number of PE nodes O(Log S)R: number of VPN RoutesV: number of VPN instancesAll Rights Reserved Alcatel-Lucent 2007

VPN Scaling: Basic configL2VPNL3VPNPEPEPEPLDT-PECP: sessionsiBPEPEPEPEPEGPPEO(N) per PEO(N) per PEO(N 2) totalO(N 2) totalCP: stateO(M*V)O(R*V)CP: CPULDP complexityBGP complexityCP: SignalingO(N) PW signalingO(R*V) route propagationDP: stateO(M*V)O(R*V)DP: computationalO(Log M) lookupO(N) per replicated packetO(Log R) lookup11 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Basic setup: scaling aspectsNumber of PEs and protocols sessions toconfigure and bring upNumber of PW/Route labels to signalReplication overheadAMAC address table/RIB sizeJMAC: AMAC: BMAC: CMAC: DMAC: EMAC: FMAC: GMAC: HMAC: IMAC: JIAll Rights Reserved Alcatel-Lucent 2007CDMAC: AMAC: BMAC: CMAC: DMAC: EMAC: FMAC: GMAC: HMAC: IMAC: JMAC: AMAC: BMAC: CMAC: DMAC: EMAC: FMAC: GMAC: HMAC: IMAC: JMAC: AMAC: BMAC: CMAC: DMAC: EMAC: FMAC: GMAC: HMAC: IMAC: JH12 MPLS Japan 2007 Oct 10, 2007BMAC: AMAC: BMAC: CMAC: DMAC: EMAC: FMAC: GMAC: HMAC: IMAC: JGFE

Hierarchical ConfigurationL3 VPNs: Hierarchical MPLS/BGPL2 VPNs: H-VPLS Hub-n-spoke T-LDP RRs for iBGP No multicast optimizations No multicast -LiBPEPEPEPEPECNPEPEPEPES: number of sitesN: number of PE nodes O(Log S)C: number of H-VPLS core nodesM: number of MAC addressesV: total number of VPN instancesv: VPN instances at PE13 MPLS Japan 2007 Oct 10, 2007CNPECNGPS: number of sitesN: number of PE nodes O(Log S)C: number of RRsR: number of VPN RoutesV: number of VPN instancesv: VPN instances at PEAll Rights Reserved Alcatel-Lucent 2007

VPN Scaling: NPLDTCNPEPEGPiBCNPEPEPECP: sessionsPEPECNPEPEPEPEPE: O(1)PE: O(1)CN: O(C)CN: O(C)CP: statePE: O(M*v)CN: O(M*V)PE: O(R*v)CN: O(R*V)CP: CPUPE: O(LDP)CN: O(LDP * C)PE: O(BGP)CN: O(BGP * C)CP: SignalingPE: O(1 PW)CN: O(N PW)PE: O(R*v) route propagationCN: O(R*V)DP: statePE: O(M*v)CN: O(M*V)PE: O(R*v)CN: O(R*V)DP: computationalO(Log M) lookupO(Log R) lookupPE: O(1) per replicated packetCN: O(N) per replicated packet14 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Scaling Multicast: Default OperationRcv’erMcastMcast pktpktMcastMcast pktpktRcv’erMcastMcast pktpktGPiBPLDT-McastMcast pktpktMcastMcast pktpktMcastMcast pktpktSourceDefault multicast replication in VPLS isflooding:No multicast in MPLS/BGP VPN basicoperation O(N) per replicated packet BW inefficiency15 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Efficient Multicast t pktpktMcastMcast pktpktMcastMcast pktpktMcastMcast pktpktRcv’erRcv’erPLDT-McastMcast pktpktMcastMcast pktpktMcastMcast pktpktMcastMcast pktpktVPLS multicast optimizationsMPLS/BGP multicast support: IGMP snooping Pre-built mcast tree (PIM-SSM) H-VPLS replication Mcast packets encapsulated in GRE BW suboptimalities still possible16 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

Scaling VPLS services further: MAC-in-MAC for VPLSPEPE PEs aggregate traffic to B-PEsPE Possible PEto use lationB-PEB-PEPEB-PEPE B-PEs performMAC-in-MACencapsulation before H-VPLSB-PESPLVCNH-PECNPEB-PEPEB-PE CNs only see B-PE’s MAC addressesCNPECNPEB-PEB-PEPEPECN scaling substantially improved:PE State: O(B) MAC addressesPEPEB is number of B-PEs Log NPE19 MPLS Japan 2007 Oct 10, 2007PEB-PEPEAll Rights Reserved Alcatel-Lucent 2007

Management & Operations: scaling aspectsL2 VPNL3 VPN T-LDP: needs provisioning MP-BGP: needs provisioning MACs: need to be controlled VPN Routes: need to be controlled OAM: VPN-aware tools needed OAM: VPN-aware tools neededScalable provisioning platform is a mustImplementations need fine controlover MAC table populationImplementations need control overlearned and propagated VPN routesOAM tools to look for:OAM tools to look for: VPLS MAC ping VRF ping VPLS MAC traceroute VRF traceroute VPLS MAC populate/purge20 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007

SummaryVPLS and MPLS/BGP VPN technologies: Different scaling aspects (MAC addresses vs IP routes) Different scaling improvement methods Yet similar operational impact and approach21 MPLS Japan 2007 Oct 10, 2007All Rights Reserved Alcatel-Lucent 2007