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Deploying MPLS Traffic Engineering

Deploying MPLS Traffic Engineering. Rodrigo Linhares rlinhare@cisco.com Consulting Systems Engineering Latin America Core Technologies Group. What It Is, How It Works, and How to Use It. 2. Agenda. How MPLS-TE Works Basic Configuration Knobs! Knobs! Knobs! Deploying and Designing.

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Deploying MPLS Traffic Engineering

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  1. Deploying MPLS Traffic Engineering Rodrigo Linhares rlinhare@cisco.com Consulting Systems Engineering Latin America Core Technologies Group

  2. What It Is, How It Works, and How to Use It 2

  3. Agenda • How MPLS-TE Works • Basic Configuration • Knobs! Knobs! Knobs! • Deploying and Designing

  4. How MPLS-TE Works • How MPLS-TE works • What good is MPLS-TE? • Information distribution • Path calculation • Path setup • Forwarding traffic down a tunnel

  5. What Good Is MPLS-TE? • There are three kinds of networks • 1. Those that have plenty of bandwidth everywhere • 2. Those with congestion in some places, but not in others • 3. Those with constant congestion everywhere • The first kind always evolves into the second kind!

  6. What Good Is MPLS-TE? • MPLS-TE introduces a 4th kind: • 1. Those that have plenty of bandwidth everywhere • 2. Those with congestion in some places, but not in others • 3. Those with constant congestion everywhere • 4. Those that use all of their bandwidth to its maximum efficiency, regardless of shortest-path routing! • MPLS-TE can help turn #2 into #4 • If you have #1, you probably don’t need MPLS-TE—yet • If you have #3, you’re stuck—you either need morebandwidth (or less traffic)

  7. Multi protocol label switching—traffic engineering Magic problemsolving labor substitute which is totally effortless What Good Is MPLS-TE? What Is MPLS-TE? What Is It Not? This Stuff Takes Work, but It’s Worth It!!!

  8. Information Distribution • You need a link-state protocol as your IGP • IS-IS or OSPF • Link-state requirement is only for MPLS-TE! • Not a requirement for VPNs, etc!

  9. Need for a Link-State Protocol • Why do I need a link-state protocol? • To make sure info gets flooded • To build a picture of the entire network

  10. Cost Node Next-Hop B 10 B C 10 C 20 D C E B 20 F B 30 G 30 B Router F OC-3 OC-3 DS3 OC-3 DS3 OC-3 DS3 The Problem with Shortest-Path • Some links are DS3, some are OC-3 • Router A has 40Mb of traffic for Route F, 40Mb of traffic for Router G • Changing to A->C->D->E won’t help • Massive (44%) packet loss at Router B->Router E! Router B 35Mb Drops! Router E Router A Router G 80Mb Traffic Router C Router D

  11. What MPLS-TE Address Cost Node Next-Hop • Router A sees all links • Router A computes paths on properties other than just shortest cost • No link oversubscribed! B 10 B C 10 C 20 D C E B 20 F Tunnel 0 30 Tunnel 1 G 30 Router B Router F OC-3 OC-3 Router E Router A DS3 Router G 40Mb OC-3 40Mb DS3 OC-3 DS3 Router C Router D

  12. How MPLS-TE Works • How MPLS-TE works • What good is MPLS-TE? • Information distribution • Path calculation • Path setup • Forwarding traffic down a tunnel

  13. Information Distribution • IS-IS • Uses Type 22 TLVs • See draft-ietf-isis-traffic • OSPF • Uses type 10 (opaque area—local) LSAs • See draft-katz-yeung-ospf-traffic

  14. Information Distribution • IS-IS and OSPF propagate the same information! • Link identification • TE metric • Bandwidth information (physical, reserveable, available) • Attribute flags

  15. Information Distribution • TE flooding is local to a single {area|level} • Inter-{area|level} TE harder, but possible (think PNNI)

  16. How MPLS-TE Works • How MPLS-TE works • What good is MPLS-TE? • Information distribution • Path calculation • Path setup • Forwarding traffic down a tunnel

  17. Path Calculation • Modified Dijkstra at tunnel head-end • Often referred to as CSPF • Constrained SPF • …or PCALC (path calculation)

  18. Router F Path Calculation Cost Node Next-Hop • PCALC takes bandwidth, other constraints into account • Paths calculated, resources reserved if necessary • End result: Bandwidth used more efficiently! B 10 B C 10 C 20 D C E B 20 F Tunnel 0 30 Tunnel 1 G 30 Router B OC-3 OC-3 Router E Router A DS3 Router G 40Mb OC-3 40Mb DS3 OC-3 DS3 Router C Router D

  19. Path Calculation • What if there’s more than one path that meets the minimum requirements (bandwidth, etc.)? • PCALC algorithm: • Find all paths with the lowest IGP cost • Then pick the path with the highest minimum available bandwidth along the path • Then pick the path with the lowest hop count (not IGP cost, but hop count) • Then just pick one path at random

  20. How MPLS-TE Works • How MPLS-TE works • What good is MPLS-TE? • Information distribution • Path calculation • Path setup • Forwarding traffic down a tunnel

  21. Path Setup • Cisco MPLS-TE uses RSVP • RFC2205, plus draft-ietf-mpls-rsvp-lsp-tunnel (RSVP-TE) • Once the path is calculated, it is handed to RSVP • RSVP uses PATH and RESV messages to request an LSP along the calculated path

  22. = PATH messages = RESV messages Router F Path Setup • PATH message: “Can I have 40Mb along this path?” • RESV message: “Yes, and here’s the label to use” • LFIB is set up along each hop Router B Router E Router A Router G Router C Router D

  23. How MPLS-TE Works • How MPLS-TE works • What good is MPLS-TE? • Information distribution • Path calculation • Path setup • Forwarding traffic down a tunnel

  24. Forwarding Traffic Down a Tunnel • There are three ways traffic can be forwarded down a TE tunnel • Auto-route • Static routes • Policy routing • With the first two, MPLS-TE gets you unequal cost load balancing

  25. Auto-Route • Auto-route = “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)

  26. Router B Router F Router H Router E Router A Router G Router I Router C Router D Auto-Route This Is the Physical Topology

  27. Router F Auto-Route • This is Router A’s logical topology • By default, other routers don’t see the tunnel! Router B Router H Router E Router A Router G Tunnel1 Router I Router C Router D

  28. Cost Node Next-Hop B 10 B C 10 C 20 D C E B 20 B F 30 G Tunnel 1 30 40 H Tunnel 1 40 I Tunnel 1 Router B Router F Router H Router E Router A Router G Router I Router C Router D Auto-Route • Router A’s routing table, built via auto-route • Everything “behind” the tunnel is routed via the tunnel Tunnel1

  29. Unequal Cost Load Balancing • IP routing has equal-cost load balancing, but not unequal cost* • MPLS-TE does unequal cost load balancing, using 16 hash buckets for next-hop, shared in rough proportion to configured tunnel bandwidth or load-share value *EIGRP Has ‘Variance’, but That’s Not As Flexible

  30. Unequal Cost: Example Router F Router E Router A 40MB Router G 20MB gsr1#show ip route 192.168.1.8 Routing 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 2 192.168.1.8, from 192.168.1.8, via Tunnel1 Route metric is 83, traffic share count is 1

  31. Router F Router E Router A Router G Unequal Cost: Example 40MB 20MB gsr1#sh ip cef 192.168.1.8 internal ……… Load distribution: 0 1 0 1 0 1 0 1 0 1 0 0 0 0 0 0 (refcount 1) Hash OK Interface Address Packets Tags imposed 1 Y Tunnel0 point2point 0 {23} 2 Y Tunnel1 point2point 0 {34} ……… Note That the Load Distribution Is 11:5—Very Close to 2:1, but Not Quite!

  32. Router B Router F Router H Router E Router A Router G Router I Router C Router D Static Routing RtrA(config)#ip route H.H.H.H 255.255.255.255 Tunnel1

  33. Cost Node Next-Hop B 10 B C 10 C 20 D C E B 20 B F 30 G 30 B 40 H Tunnel 1 40 I B Router B Router F Router H Router E Router A Router G Router I Router C Router D Static Routing • Router H is known via the tunnel • Router G is not routed to over the tunnel, even though it’s the tunnel tail! Tunnel1

  34. Router F Router E Router A Router G Static Routing 40MB 20MB gsr1(config)#ip route 1.2.3.4 255.255.255.255 192.168.1.11 gsr1#sh ip cef 1.2.3.4 ……… Load distribution: 0 1 0 1 0 1 0 1 0 1 0 0 0 0 0 0 (refcount 1) Hash OK Interface Address Packets Tags imposed 1 Y Tunnel0 point2point 0 {23} 2 Y Tunnel1 point2point 0 {34} ……… Static Routes Inherit Unequal Cost Load-Sharing When Recursing through a Tunnel

  35. Router B Router F Router H Router E Router A Router G Router I Router C Router D Policy Routing RtrA(config-if)#ip policy route-map set-tunnel RtrA(config)#route-map set-tunnel RtrA(config-route-map)#match ip address 101 RtrA(config-route-map)#set interface Tunnel1 Tunnel1

  36. Cost Node Next-Hop B 10 B C 10 C 20 D C E B 20 B F 30 G 30 B 40 H B 40 I B Router B Router F Router H Router E Router A Router G Router I Router C Router D Policy Routing • Routing table isn’t affected by policy routing • Need (12.0(16)ST or 12.2T) or higher for ‘set interface tunnel’ to work Tunnel1 Tunnel1

  37. Forwarding Traffic down a Tunnel • You can use any combination of auto-route, static routes, or PBR • …But simple is better unless you have a good reason • Recommendation: Either auto-route or statics to BGP next-hops, depending on your needs

  38. Agenda • Prerequisites • How MPLS-TE Works • Basic Configuration • Knobs! Knobs! Knobs! • Deploying and Designing

  39. (globally) ip cef {distributed} mpls traffic-eng tunnels (per interface) mpls traffic-eng tunnels Basic Midpoint/Tail Configuration

  40. (if IGP = OSPF) router ospf <x> mpls traffic-eng router-id Loopback0 mpls traffic-eng area <y> Basic Midpoint/Tail Configuration

  41. (if IGP = IS-IS) router isis <x> mpls traffic-eng router-id Loopback0 mpls traffic-eng level-{1,2} metric-style wide Basic Midpoint/Tail Configuration

  42. Basic Head-End Configuration • Head-end needs the 4–5 ‘mid/tail’ lines • But wait—there’s more!

  43. Basic Head-End Configuration • Create the tunnel interface interface Tunnel0 ip unnumbered Loopback0 tunnel mode mpls traffic-eng tunnel source Loopback0 tunnel destination <tunnel endpoint> tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng path-option 10 dynamic

  44. Basic Head-End Configuration • Total configuration: • 1 line globally • 1 line per interface • 2 lines if OSPF • 3 lines if IS-IS • + 7 lines per tunnel at head-end • Not really much to the basic configuration

  45. Agenda • Prerequisites • How MPLS-TE Works • Basic Configuration • Knobs! Knobs! Knobs! • Deploying and Designing

  46. Knobs! Knobs! Knobs! • Influencing the path selection • Auto-bandwidth • Fast reroute • DiffServ-Aware Traffic Engineering

  47. Knobs! Knobs! Knobs! • Influencing the path selection • Bandwidth • Priority • Administrative weight • Attributes and affinity

  48. Bandwidth ip rsvp bandwidth <x> • Per-interface command • X = amount of reservable BW, in K • Default: X=75% of link bandwidth

  49. Bandwidth tunnel mpls traffic-eng bandwidth <Kb> • Per-tunnel command • Tunnel default: 0 Kb

  50. Priority • Configured on tunnel interface • S = setup priority (0–7) • H = holding priority (0–7) • Lower number is more important, or better tunnel mpls traffic-eng <S> {H}

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