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Smart IP Switching A Hybrid System for Fast IP-based Network Backbones

Smart IP Switching A Hybrid System for Fast IP-based Network Backbones. David Lloyd Donal O’Mahony. IP over ATM. Conventional IP routers have become a bandwidth bottleneck ATM technology offers high bandwidth capability

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Smart IP Switching A Hybrid System for Fast IP-based Network Backbones

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  1. Smart IP Switching A Hybrid System for Fast IP-based Network Backbones David Lloyd Donal O’Mahony

  2. IP over ATM • Conventional IP routers have become a bandwidth bottleneck • ATM technology offers high bandwidth capability • IP over ATM schemes have been developed to support IP over and ATM Network • Classical IP over ATM • Next Hop Resolution Protocol (NHRP) • LAN Emulation (LANE) • Multi-Protocol Over ATM (MPOA)

  3. Heavyweight Nature of Emulation Techniques IP Network Emulation Scheme ATM Network Overlay Model

  4. IP on ATM Hardware • IP implemented directly on ATM hardware • Schemes may be categorised by the approach they employ for setting up switched paths through a network • Principal Approaches are: • Traffic-Driven • - Nature of traffic drives switch path establishment • - (Ipsilon’s IP Switching and Toshiba’s CSR) • Control-Driven • -Switched paths set up before data traffic flows • - (Cisco’s Tag Switching and IBM’s ARIS)

  5. Traffic-Driven Approaches • Advantages • Switched paths are only set up for long-lived flows • Schemes are non-complex • Resilient in event of failure • Scalable • Disadvantages • Flow aggregation is not an inherent property of the scheme • Short-lived Flows that recur consistently can cause excessive control traffic

  6. Flow Merging in Control-driven Schemes • VC Merge • The merging of one or more incoming VCs into the same outgoing VC • Requires special VC merge-capable ATM hardware • VP Merge • The merging of one or more incoming Virtual Paths (VPs) onto the same outgoing VP • It is imperative to ensure that active VCs are not merged • Block allocation of VCIs Required

  7. AAL-5 Cell Interleave

  8. Control-Driven Approaches • Advantages • No delay in setting up a dedicated VC on a flow by flow basis • All IP packets are switched at layer 2 • Disadvantages • Dedicated-VCs are established for all routes • Schemes are Complex

  9. Multi-Protocol Label Switching • In early 1997 the IETF Multi-Protocol Label Switching (MPLS) working group was established. • The group issued a framework document, which attempts to: • Provide a coherent description of the major approaches • Discuss the technical issues involved • Lay the way forward for standardisation

  10. Introduction to Smart IP Switching • Smart IP Switching is a new traffic-driven scheme that exhibits advantages of both the traffic-driven and control-driven approaches. • The main benefits of Smart IP Switching are: • The Introduction of flow aggregation into a traffic-driven scheme • The definition of short-term and long-term VCs • Increasing the proportion of IP packets switched at layer 2

  11. Smart IP Switching Concepts • The key concepts that define Smart IP Switching are: • Unique Flow Identifier - Flow Identification • Flow aggregation - Based on CIDR prefixes • Ingress-piping - Merging flows at an ingress node • Virtual Merge - Merging flows at intermediate nodes • Longevity of VCs - short-term and long term VCs

  12. Flow Identification • The Unique Flow Identifier identifies Ipsilon flow types plus a new flow type (flow type 3) • Flow type 3 is specifically defined to represent aggregate flows

  13. Smart IP Switch Representation

  14. Smart IP Switch Operation (1) first packet first packet first packet Default VC Default VC Default VC P1 P2 P2 P2 P1 SIPS3 SIPS1 SIPS2 P1 first packet IFMP REDIRECT IFMP REDIRECT IFMP REDIRECT LAN1 P1=port 1 P2=port 2 SIPS Operation (First Packet) Default VC Default VC Default VC SIPS3 SIPS1 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 VPI=0 LAN1 Ingress-pipe VCI=32 VCI=32 Ingress-pipe VCI=32 SIPS Operation (Dedicated VCs)

  15. Smart IP Switch Operation (2) Default VC Default VC Default VC SIPS3 SIPS1 SIPS2 second packet P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 VPI=0 LAN1 Ingress-pipe VCI=32 VCI=32 VCI=32 second packet packet) SIPS Operation (Second Default VC Default VC SIPS3 SIPS1 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 VPI=0 LAN1 Ingress-pipe VCI=32 VCI=32 VCI=32 Cut-through second packet SIPS Operation (First Cut-through) Down-piping

  16. Smart IP Switching Operation (3) Default VC Default VC SIPS3 SIPS1 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 VPI=0 LAN1 Ingress-pipe Ingress-pipe VCI=32 VCI=32 VCI=32 VCI=33 VCI=33 second packet Cut-through Cut-through SIPS Operation (Second Cut-through)

  17. Ingress-pipe at Intermediate Node FDDI : LAN P1=port 1 P2=port 2 Default VC Default VC SIPS3 SIPS1 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 VPI=0 LAN1 Ingress-pipe VCI=32 VCI=32 VCI=32 VCI=33 VCI=33 VCI=35 Cut-through SIPS Operation (Intermediate Ingress-Pipe)

  18. Virtual Merge ingress node P1 P2 P2 P2 P1 SIPS3 SIPS1 SIPS2 P1 egress node ingress-pipe Dedicated VC LAN1 P1=port 1 next available VC Dedicated VC P2=port 2 P2 SIPS4 default VCs omitted P1 virtual merge for clarity ingress-pipe LAN2 SIPS Operation (Virtual Merge)

  19. Ingress-Piping SIPS4 LAN1 LAN3 SIPS1 SIPS3 SIPS2 network :172.16.0.0 10/100 Mb Ethernet links LAN2 10 Mb Ethernet LAN

  20. Flow Management • Flow Information Base (FIB) used to manage flows • Ipsilon flow types are created and refreshed as normal • Detection of a potential aggregate flow is based existence of a CIDR prefix • Flow type 3 is refreshed by sending an REDIRECT message with a redirect message element attached for every upstream ingress-pipe that remains active • Referesh of VCs is managed on a localised scope

  21. Longevity of VCs • The first time a flow is detected, it is set up as short-term • A VC used by many flows is transitioned to long-term • VCs for flows that recur are set up as long-term • Long-term VCs do not have to be refreshed as often as short-term VCs

  22. VC Pool • The use of a VC pool eliminates the delay incurred in setting up a VC • A suitable strategy to manage VC pool size must be employed • VCs may be expensive • Packets arriving on an unassigned VC must be associated with the relevant flow type 3 • The use of a VC pool has been discussed in the literature

  23. CIDR Fall-back Routing table entry Routing table entry Routing table entry 172.16.0.0 172.16.3.0 172.16.0.0 Default VC Default VC SIPS1 SIPS3 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 LAN1 Network: 172.16.3.0 VCI=32 VCI=32 Based on UFI prefix Based on UFI prefix 172.16.0.0 172.16.3.0 Host: 172.16.3.1

  24. CIDR-Fall-back (2) Routing table entry Routing table entry Routing table entry 172.16.0.0 172.16.3.0 172.16.0.0 Default VC Default VC SIPS1 SIPS3 SIPS2 P1 P2 P2 P1 P2 P1 VPI=0 VPI=0 LAN1 Network: 172.16.3.0 VCI=32 VCI=32 VCI=33 Based on UFI prefix 172.16.3.0 Based on UFI prefix 172.16.3.0 Host: 172.16.3.1

  25. Simulated Network

  26. Simulation Results

  27. Summary • Smart IP Switching: • Is a new traffic-driven IP on ATM hardware scheme modelled on Ipsilon’s IP Switching • Introduces Flow Aggregation into the traffic driven-scheme • Introduces the concept of short-term and long-term VCs • Significantly increases the proportion of IP Packet that are diverted from being forwarded (layer 3) to being switched (layer 2) • - A performance level that is comparable to that of the control-driven approaches, while retaining the simplicity, scalability and reliability of the traffic-driven approach

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