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Multiple Protocol Over ATM (MPOA)

Multiple Protocol Over ATM (MPOA). 中正資工 黃仁竑. MPOA. MPOA integrates LANE and NHRP to preserve benefits of LANE while allowing inter-subnet communication over ATM SVCs without routers in the data path. Virtual Routing: splitting forwarding and routing Routing: MPOA Server (MPS)

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Multiple Protocol Over ATM (MPOA)

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  1. Multiple Protocol Over ATM (MPOA) 中正資工 黃仁竑

  2. MPOA • MPOA integrates LANE and NHRP to preserve benefits of LANE while allowing inter-subnet communication over ATM SVCs without routers in the data path. • Virtual Routing: splitting forwarding and routing • Routing: MPOA Server (MPS) • Route discovery, topology management • Usually resides in an ATM switch-router or ATM attached router • Forwarding: MPOA Client (MPC) • Forward with shortcut VCC • edge devices (to legacy LAN) or ATM attached hosts • Incorporates LANE and NHRP • Support the transfer of inter-subnet traffic in LANE • Use LANE for Layer 2 service • MPS use NHRP for route calculations • MPC use NHRP to establish VCC for shortcuts

  3. MPOA Components • MPOA Server (MPS) • MPS and MPC are connected through LANE • Provides layer 3 forwarding information to MPCs • Includes an NHRP Server function for path discovery • MPOA Client (MPC) • Acts as a point of entry and exit for shortcut VCCs • Communicates with MPS using NHRP • Provides layer 3 forwarding as well as looking for chance to create shortcuts • MPC Cache • Ingress Cache • Information to resolve layer 3 address to and ATM address or VCC • Used to detect flows that can use a shortcut VCC • Egress Cache • Information to encapsulate and forward layer 3 datagrams coming from a shortcut VCC

  4. MPOA Information Flows • MPOA control flows • Configuration flow • For knowing the LANE configuration (LECS, LEC, BUS) • MPC-MPS control flow • For route information • MPS-MPS control flow • Routing protocols and NHRP for route calculation • MPC-MPC control flow • For error report for misdirected packets • MPOA data flows • MPC-MPC data flow • on shortcut VCCs • MPC-NHC data flow • send unicast data to an MPC

  5. MPOA Flow MPS MPS • Basic idea LANE Default path LANE LANE Shortcut VCC MPC MPC

  6. MPOA Flow • MPOA host to MPOA host • shortcut between two ATM hosts • Edge device to MPOA host • shortcut between edge device and ATM host • ingress MPC • Edge device to edge device • shortcut between two edge devices • ingress MPC and egress MPC

  7. Ingress Cache hit? Egress Cache hit? Valid short- cut? MPS MAC hit? Threshold Exceed? Request Out? Logic Flow for MPC Egress MPC Ingress MPC yes yes yes Error Report no no no no Count frame Create Cache yes yes yes Send on shortcut Arrive on shortcut no no Send Request From LANE Out to LANE

  8. Flow for MPS • When received an MPOA resolution request from a MPC • If ingress MPS is able to resolve it, return a reply. (within the same LANE or in cache) • If the address is non-local, sends the request through the routed path (with its address as the source address) • When the request arrives at the egress MPS serving the destination MPC, the egress MPS constructs an MPOA Cache Imposition Request and sends it to the egress MPC. • The Cache Imposition Request provides encapsulation and state maintenance information needed by egress MPC. • After receiving reply from egress MPC, the egress MPS send back a NHRP resolution reply packet to the ingress MPS • On receiving the NHRP reply packet, the ingress MPS returns a MPOA resolution reply to the ingress MPC.

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