3 Use cases Use case 1: Mobile backhaul DRNI In LTE mobile backaul, one optional solution is deploying routers and layer 2 network(PTN). For the interconnection between routers and PTN, DRNI is an appropriate mechanismRouter is the Layer 3 gateway of eNodeBs. In this case, DRNI is used on layer 3 gateway devicesFurthermore, In the best case convergence time should be less than 200ms, in the worst case it should be less than 500msDRNIUse case 2: Layer 2 network in cloud computation IDCIn cloud computation IDC, we use layer 2 network to meet the requirement of cloud computation. We want to use DRNI instead of spanning tree (Of course, SPB or Trill are also optional, maybe in the future)Core switch is the layer 3 gateway of servers. In this case, DRNI is used on layer 3 gateway devicesFurthermore, convergence time should be less than 500msDRNIVM migrationSearchingDatebase accessDRNIWe want to use DRNI on layer 3 gateway devicesWe require fast convergence in DRNI for protection
5 Requirement(1) Unique MAC for DRNI Layer 3 networkFor hosts there should be only one gateway, so GW1 and GW2 should share the same MAC and IP address for LA1 (the distributed link aggregation group)When hosts request GW’s ARP, GW1 and GW2 should answer the same ARP ( GW_IP, unique MAC)When GW1 and GW2 request hosts’ ARP, they should use the same sender ARP info ( GW_IP, unique MAC)Because GW1 and GW2 will use LA1’s MAC as their ARP MAC, so DRNI should make sure that nodes in the same DAS share an unique MAC which could be used by upper layer protocol (e.g. ARP)We can config the same IP on LA1 of GW1 and GW2. It doesn’t depend on DRNI protocolGW1GW2LA1LA2L2SW1L2SW2Layer 2 networkL2SWHostARP RequestARP Reply
6 Requirement(2) L3 entries Backup mechanism To obtain fast protection switch, GW1 and GW2 should share the same L3 entries (e.g. ARP entries). When GW1 or link between GW1 and L2SW1 break down, GW2 could forward all flows immediatelyReal-time backupWhen GW1 receives ARP request or ARP reply packet from host, it should duplicate one and send to GW2When GW2 receives ARP request or ARP reply packet from host, it should duplicate one and send to GW1GW1 and GW2 could limit the duplication based on the ETH_TYPE of packets ( for ARP, it’s 0x0806)This mechanism could not used in the below scenarioBatch backupWhen GW1 reboots, batch backup(with GW2) can help GW1 recover forwarding all flows as soon as possible. Otherwise GW1 wil take even a few seconds to relearn ARP entries and introduce a long interruptionHow to fulfill batch backup is under research ( through ICCP, LACP or ARP )Of course, if we define a protocol for batch backup, it also could be used for real-time backupLayer 3 networkGW1GW2L2SW1L2SW2Layer 2 networkHostARP Request or ReplayLayer 2 networkLayer 3 networkGW1GW2L2SW1L2SW2HostBatch backup message
8 ProposalWhen using DRNI on layer 3 gateway devices, DRNI should support the following featuresNodes in the same DAS share an unique MAC for LA groupA node could duplicate some certain packets to the other nodes in the same DAS based on ETH_TYPE of packetsNodes in the same DAS could fulfill batch backup of certain entries (e.g. ARP entries) with each other
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