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discussion on adding migration bit in VDP

discussion on adding migration bit in VDP. liyizhou@huawei.com. Contents. Recap the proposal Questions from last meeting and answers. proposal: a dding a “migration” bit in VDP request?. M bit: 1 = migrated VDP request 0 = newly started VDP request. M. What can be done with the M-bit?.

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discussion on adding migration bit in VDP

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  1. discussion on adding migration bit in VDP liyizhou@huawei.com

  2. Contents • Recap the proposal • Questions from last meeting and answers

  3. proposal: adding a “migration” bit in VDP request? M bit: 1 = migrated VDP request 0 = newly started VDP request M

  4. What can be done with the M-bit? • to facilitate switch port configuration and restore the states • DHCP snooping based filtering • Multicast group join

  5. NIC NIC With M-bit, how to deal with DHCP snooping based filtering? (1) • Problems: ToR port snoops DHCPACK and binds IP/MAC/port to filter the following traffic. When VM moves, VM won’t resend DHCP request and hence new port won’t listen any DHCPACK. Therefore filter won’t be enabled on new port. 6 migration 6. VM migration. VM VM VM VM vSwitch vSwitch Server Server 5. DHCPACK 1. DHCP request 1 5 4. DHCP Snooping and set up IP/MAC /port filter 7. DHCP Snooping based filter on new port. How? 7 TOR 4 2. DHCP Request 2 DCN Note：DHCP Discover and DHCP Offer exchanges are ignored in picture 3 3. DHCP Ack DHCP Server

  6. NIC NIC With M-bit, how to deal with DHCP snooping based filtering? (2) • With M bit: trigger some standard DHCP in-band mechanism to be used. E.g. DHCP leasequery 1 migration 1. VM migration. VM VM VM VM vSwitch vSwitch Server Server 2. VDP request w/ M bit 2 6。VDP response 6 TOR 5. DHCP Snoops ACK and set up IP/MAC /port filter 5 3. DHCP leasequery 3 4 4. DHCP Ack DHCP Server

  7. NIC NIC With M-bit, how to deal with multicast group member movement? (1) • Problems: VM1 sends IGMP join so that ToR would have a multicast membership list including VM1 on certain port for certain multicast group address. After migration, VM1 won’t resend IGMP join as it has no awareness of movement of itself. Multicast membership list won’t have VM1’s info enabled on new port until vm1 receives and responds the general IGMP query from IGMP querier. 3、vm migration 3 Server Server VM VM VM VM vSwitch vSwitch 2、multicast group traffic 1、IGMP JOIN 2 1 4. New port joins VM’s multicast groups. How? TOR TOR IGMP 查询器 GW IGMP querier GW

  8. NIC NIC With M-bit, how to deal with multicast group member movement? (2) • With M bit: trigger some standard IGMP in-band mechanism to be used. E.g. new ToR port fakes IGMP query to VM 1 1.VM migration Server Server VM VM VM VM vSwitch vSwitch 2 4. IGMP report 4 2. VDP request w/ M bit 3 3. IGMP query TOR TOR IGMP 查询器 GW IGMP querier GW

  9. Questions from last meeting (1) • Q: Without M bit, we can still use standard VDP associate to trigger the DHCP/IGMP behavior we want. • A: No, because of the timing. M bit (migration completes) is a signal to do the triggering at the right time. Conventional VDP is not strictly coupled to VM’s state. (see next slide). Wrong timing implies the high possibility to get wrong information.

  10. VM migration scenario ‘old’ EVB Station ‘old’ EVB Bridge ‘new’ EVB Bridge ‘new’ EVB Station assoc_req assoc_rsp Uncertain time duration VSI power on Dataframe Start migration assoc_req VSI can still join/leave multicast group and update its DHCP lease Dataframe assoc_rsp Dataframe Uncertain time duration Migration completes assoc_req w/ M-bit Trigger DHCP/IGMP procedures assoc_rsp • Conclusion: • M-bit indicates the completion of the migration which is the right time to trigger DHCP/IGMP procedures described before • pre-assoc/assoc can be sent at any time, it is not coupled to the migration state of VSI. And it is also used for keepalive.

  11. Questions from last meeting (2) • Q: Can hypervisor perform like DHCP relay/IGMP relay to send the DHCP leasequery and IGMP query instead of bridge? • A: Hypervisor could do that but we believe it would be better to put all the functions on adjacent bridge for the following reason • Bridges have already implemented the features like DHCP relay or IGMP relay/proxy. There is little extra functions required. While hypervisors are not. • There may come more real time configurations/provisions other than DHCP/IGMP in future. It is tedious to have hypervisor add features on demands of network requirements every time.

  12. Questions from last meeting (3) Q: Can hypervisor know the state of VM? A: Yes. Take VMWare’s vSphere as example. It has the event to indicate the start and end of a migration with event type VmBeingHotMigratedEvent and VmMigratedEvent. Hence it is considered implementation practical for hypervisor being able to set M bit at right time.

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