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1、MPLS TE TOI,Agenda,How MPLS TE worksWhat Code Is MPLS TE In?Platform Issues in ImplementationLab Demo-config,How MPLS TE Works,PrerequisitesHow MPLS-TE WorksBasic ConfigurationKnobs!Knobs!Knobs!Deploying and Designing,Prerequisites,You should already understandHow to configure a Cisco routerBasic MP
2、LS concepts like push/pop/swap,EXP,and LFIBHow a link-state routing protocol worksBasic QoS mechanisms like MDRR and LLQ,Agenda,PrerequisitesHow MPLS-TE WorksBasic ConfigurationKnobs!Knobs!Knobs!Deploying and Desiginig,How MPLS-TE Works,How MPLS-TE WorksWhat good is MPLS-TE?Information DistributionP
3、ath CalculationPath SetupForwarding Traffic Down A Tunnel,What Good Is MPLS-TE?,There are two kinds of networksThose that have plenty of bandwidth everywhereThose with congestion in some places,but not in othersThe first kind always evolve into the second kind!,What Good Is MPLS-TE?,MPLS-TE introduc
4、es a 3rd kind:Those that have plenty of bandwidth everywhereThose with congestion in some places,but not in othersThose that use all of their bandwidth to its maximum efficiency,regardless of shortest-path routing!,What Good Is MPLS-TE?,MultiProtocolLabelSwitching-TrafficEngineering,MagicProblem-sol
5、vingLaborSubstitute which isTotallyEffortless,This stuff takes work,but its worth it!,What is MPLS-TE?What is it not?,Information Distribution,You need a link-state protocol as your IGPIS-IS or OSPFLink-state requirement is only for MPLS-TE!Not a requirement for VPNs,etc!,Need for a Link-State Proto
6、col,Why do I need a link-state protocol?To make sure info gets floodedTo build a picture of the entire network,Need for a Link-State Protocol,Consider the following network:-All links have a cost of 10-RtrAs path to RtrE is A-B-E,cost 20-All traffic from A to E,F,G goes A-B-E,What a DV Protocol Sees
7、,RtrA doesnt see all the linksRtrA only knows about the shortest pathThis is by design,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,What a LS Protocol Sees,RtrA sees all linksRtrA only computes the shortest pathRouting table doesnt change,The Problem With Shortest-Path,Some links are DS3,some are OC3,80Mb tra
8、ffic,35Mb Drops!,RtrA has 40Mb of traffic for RtrF,40Mb of traffic for RtrG,Massive(44%)packet loss at RtrB-RtrE!,Changing to A-C-D-E wont help,What MPLS-TE Addrs,OC3,OC3,DS3,DS3,DS3,OC3,OC3,RtrA sees all linksRtrA computes paths on properties other than just shortest costNo congestion!,40Mb,40Mb,Ho
9、w MPLS-TE Works,How MPLS-TE WorksWhat good is MPLS-TE?Information DistributionPath CalculationPath SetupForwarding Traffic Down A Tunnel,Information Distribution,OSPFUses Type 10(Opaque Area-Local)LSAsSee draft-katz-yeung-ospf-traffic,Information Distribution,IS-ISUses Type 22 TLVsSee draft-ietf-isi
10、s-traffic,Information Distribution,IS-IS and OSPF propagate the same information!Link identificationTE MetricBandwidth info(max physical,max reservable,available per-class)Attribute flags,Information Distribution,TE flooding is local to a single area|levelInter-area|level TE harder,but possible(thin
11、k PNNI),How MPLS-TE Works,How MPLS-TE WorksWhat good is MPLS-TE?Information DistributionPath CalculationPath SetupForwarding Traffic Down A Tunnel,Path Calculation,Modified Dijkstra at tunnel head-endOften referred to as CSPFConstrained SPFor PCALC(path calculation),Path Calculation,Normal SPF find
12、shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,“whats the shortest pat
13、h to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of
14、SPF,RtrA,RtrB,RtrC,RtrD,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across
15、 all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the sh
16、ortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd ed),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to all routers?”,Path Calculation,Normal SPF find shortest path across all linksSee Perlman(2nd e
17、d),Moy,etc.for explanation of SPF,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to all routers?”,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router F with 40Mb av
18、ailable?”,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,“whats the shortest path to router F with 40Mb available?”,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,“
19、whats the shortest path to router F with 40Mb available?”,OC3,OC3,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrD,“whats the shortest path to router F with 40Mb available?”,OC3,OC3,DS3,Path Calculation,Constrained SPF find
20、shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,“whats the shortest path to router F with 40Mb available?”,OC3,OC3,DS3,DS3,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,Rtr
21、F,RtrG,“whats the shortest path to router F with 40Mb available?”,OC3,OC3,DS3,DS3,OC3,OC3,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router F with 40Mb available?”,Path Calcul
22、ation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router F with 40Mb available?”,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,Rt
23、rB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router F with 40Mb available?”,OC3,OC3,DS3,DS3,OC3,OC3,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,“whats the shortest path to router F with 40Mb availab
24、le?”,OC3,OC3,DS3,DS3,OC3,Path Calculation,Constrained SPF find shortest path to a specific nodeConsider more than just link cost!,RtrA,RtrB,RtrE,RtrF,“whats the shortest path to router F with 40Mb available?”,OC3,DS3,OC3,Path Calculation,“But Wait!Theres nothing different between the two SPF results
25、!”.but.,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router G with 40Mb available?”,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,“whats the shortest path to router G with 40M
26、b available?”,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,“whats the shortest path to router G with 40Mb available?”,OC3,OC3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,RtrD,“whats the shortest path to router G
27、 with 40Mb available?”,OC3,OC3,DS3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,RtrE,RtrD,“whats the shortest path to router G with 40Mb available?”,OC3,OC3,5MB,DS3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,Rt
28、rE,RtrD,“whats the shortest path to router G with 40Mb available?”,OC3,OC3,5MB,DS3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrB,RtrC,RtrD,“whats the shortest path to router G with 40Mb available?”,OC3,OC3,DS3,Path Calculation,What about the 2nd path?Available b
29、andwidth has changed!,RtrA,RtrC,RtrD,“whats the shortest path to router G with 40Mb available?”,OC3,DS3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrC,RtrE,RtrD,“whats the shortest path to router G with 40Mb available?”,OC3,DS3,DS3,Path Calculation,What about the
30、 2nd path?Available bandwidth has changed!,RtrA,RtrC,RtrE,RtrD,RtrF,RtrG,“whats the shortest path to router G with 40Mb available?”,OC3,DS3,DS3,OC3,OC3,Path Calculation,What about the 2nd path?Available bandwidth has changed!,RtrA,RtrC,RtrE,RtrD,RtrG,“whats the shortest path to router G with 40Mb av
31、ailable?”,OC3,DS3,DS3,OC3,Path Calculation,OC3,OC3,DS3,DS3,DS3,OC3,OC3,End result:bandwidth used efficiently!,40Mb,40Mb,Path Calculation,Happy!Happy!Joy!Joy!,Path Calculation,What if theres more than one path that meets the minimum requirements(BW,etc)?PCALC algorithm:find all paths with the lowest
32、IGP costthen pick the path with the highest minimum bandwidth along the paththen pick the path with the lowest hop count(not IGP cost,just hop count)then just pick one path at random,Path Calculation,all left-side linksare 10,100M,all right-side linksare 5,50M,Path Calculation,all left-side linksare
33、 10,100M,all right-side linksare 5,50M,cost,available BW,RtrA,RtrZ,Whats the bestpath from A to Z with BW of 20M?,Path Calculation,all left-side linksare 10,100M,all right-side linksare 5,50M,cost,available BW,RtrA,RtrZ,Whats the bestpath from A to Z with BW of 20M?,Path Calculation,all left-side li
34、nksare 10,100M,all right-side linksare 5,50M,cost,available BW,RtrA,RtrZ,Whats the bestpath from A to Z with BW of 20M?,Path Calculation,all left-side linksare 10,100M,all right-side linksare 5,50M,cost,available BW,RtrA,RtrZ,Whats the bestpath from A to Z with BW of 20M?,How MPLS-TE Works,How MPLS-
35、TE WorksWhat good is MPLS-TE?Information DistributionPath CalculationPath SetupForwarding Traffic Down A Tunnel,Path Setup,Cisco MPLS-TE uses RSVPRFC2205,plus draft-ietf-mpls-rsvp-lsp-tunnel,Path Setup,Once the path is calculated,it is handed to RSVPRSVP uses PATH and RESV messages to request an LSP
36、 along the calculated path,Path Setup,PATH message:“Can I have 40Mb along this path?”RESV message:“Yes,and heres the label to use.”LFIB is set up along each hop,Path Setup,Errors along the way will trigger RSVP errorsMay also trigger re-flooding of TE info if appropriate,How MPLS-TE Works,How MPLS-T
37、E WorksWhat good is MPLS-TE?Information DistributionPath CalculationPath SetupForwarding Traffic Down A Tunnel,Forwarding Traffic Down a Tunnel,There are three ways traffic can be forwarded down a TE tunnelAutorouteStatic routesPolicy routingFor the first two,MPLS-TE gets you unequal-cost load-balan
38、cing.,Autoroute,Autoroute=“use the tunnel as a directly connected link for SPF purposes”This is not the CSPF(for path determination),but the regular IGP SPF(route determination)Behavior is intuitive,operation can be confusing,Autoroute,RtrH,This is the physical topology,RtrI,Autoroute,This is RtrAs
39、logical topologyOther routers dont see the tunnel!,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,RtrH,Tunnel1,RtrI,Autoroute,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,RtrH,RtrI,Static routing,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,RtrH,RtrA(config)#ip route H.H.H.H 255.255.255.255 Tunnel1,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,Rt
40、rG,RtrH,RtrI,Static routing,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,RtrH,RtrA,RtrB,RtrC,RtrE,RtrD,RtrF,RtrG,RtrH,RtrI,Unequal-Cost Load Balancing,IP routing has equal-cost load-balancing,but not unequal-cost*Unequal-cost load balancing difficult to do while guaranteeing a loop-free topology*EIGRP has var
41、iance,but thats not as flexible,and besides,MPLS-TE and EIGRP are two different things,Unequal-Cost Load Balancing,Since MPLS doesnt forward based on IP header,permanent routing loops dont happen.16 hash buckets for next-hop,shared in rough proportion to tunnel BW,Unequal-cost,Example 1,gsr1#show ip
42、 route 192.168.1.8Routing entry for 192.168.1.8/32 Known via isis,distance 115,metric 83,type level-2 Redistributing via isis Last update from 192.168.1.8 on Tunnel0,00:00:21 ago Routing Descriptor Blocks:*192.168.1.8,from 192.168.1.8,via Tunnel0 Route metric is 83,traffic share count is 2 192.168.1
43、.8,from 192.168.1.8,via Tunnel1 Route metric is 83,traffic share count is 1,Unequal-cost,Example 1,Note that the load distribution is 11:5 very close to 2:1,but not quite!,gsr1#sh ip cef 192.168.1.8 intLoad distribution:0 1 0 1 0 1 0 1 0 1 0 0 0 0 0 0(refcount 1)Hash OK Interface Address Packets Tag
44、s imposed 1 Y Tunnel0 point2point 0 23 2 Y Tunnel1 point2point 0 34,Unequal-cost,Example 2,RtrA,RtrE,RtrF,RtrG,100MB,10MB,Q:How does 100:10:1 fit into a 16-deep bucket?,1MB,gsr1#sh ip rou 192.168.1.8Routing entry for 192.168.1.8/32 Known via isis,distance 115,metric 83,type level-2 Redistributing vi
45、a isis Last update from 192.168.1.8 on Tunnel2,00:00:08 ago Routing Descriptor Blocks:*192.168.1.8,from 192.168.1.8,via Tunnel0 Route metric is 83,traffic share count is 100 192.168.1.8,from 192.168.1.8,via Tunnel1 Route metric is 83,traffic share count is 10 192.168.1.8,from 192.168.1.8,via Tunnel2
46、 Route metric is 83,traffic share count is 1,Unequal-cost,Example 2,RtrA,RtrE,RtrF,RtrG,100MB,10MB,A:Any way it wants to!15:1,14:2,13:2:1,it depends on the order the tunnels come up.Deployment guideline:dont use tunnel metrics that dont reduce to 16 buckets!,1MB,gsr1#sh ip cef 192.168.1.8 internal L
47、oad distribution:0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0(refcount 1)Hash OK Interface Address Packets Tags imposed 1 Y Tunnel0 point2point 0 36 2 Y Tunnel1 point2point 0 37,Policy routing,RtrA(config-if)#ip policy route-map set-tunnelRtrA(config)#route-map set-tunnelRtrA(config-route-map)#match ip address 1
48、01RtrA(config-route-map)#set interface Tunnel1,Policy routing,Forwarding Traffic Down a Tunnel,You can use any combination of autoroute,static routes,or PBR.but simple is better unless you have a good reason.Recommendation:either autoroute or statics to BGP next-hops,depending on your needs.,Agenda,
49、PrerequisitesHow MPLS-TE WorksBasic ConfigurationKnobs!Knobs!Knobs!Deploying and Desiginig,Basic Configuration,Basic ConfigurationBasic Midpoint/Tail ConfigBasic Headend ConfigPath-optionBandwidth,Basic Midpoint/Tail Config,(globally)ip cef distributedmpls traffic-eng tunnels,Basic Midpoint/Tail Con
50、fig,(per interface)mpls traffic-eng tunnels,Basic Midpoint/Tail Config,(if IGP=OSPF)router ospf mpls traffic-eng router-id Loopback0 mpls traffic-eng area,Basic Midpoint/Tail Config,(if IGP=OSPF)MPLS TE is a single area only(usually area 0)RID must be set(unlike OSPF RID)Its a Very Very Good idea to
