Method, Apparatus and System for Transmitting Packets in Virtual Network with Respect to a Virtual Machine (vm) Migration

1. A method for transmitting packets in virtual network with respect to a virtual machine (VM) migration, comprising: receiving, by a top of rack (TOR) switch, a Layer 2 frame carrying a virtual network identifier (VNID); wherein the TOR switch is the designated node (DN) corresponding to the VNID carried in the Layer 2 frame; extracting, by the TOR switch, a Layer 3 destination address from the Layer 2 frame; determining, by the TOR switch, whether a VM corresponding to the Layer 3 destination address is in the TOR switch or the VM has migrated; determining, by the TOR switch, another TOR switch to which the VM was migrated, according to the VNID and the Layer 3 destination address, when the VM has migrated, and transmitting, by the TOR switch, the Layer 2 frame to the another TOR switch to which the VM migrated.

2. The method according to claim 1 , wherein determining another TOR switch comprises: looking up, by the TOR switch, a Layer 2 table according to the Layer 3 destination address, and determining the another TOR switch to which the VM was migrated; wherein the Layer 2 table indicates at least one of the following: a mapping between a VM Internet Protocol (IP) address and a TOR switch media access control (MAC) address for a migrated VM and a mapping between a VM IP address and a VM MAC address for a non-migrated VM.

3. The method according to claim 1 , further comprising: determining a MAC address of the VM according to the VNID and the Layer 3 destination address, when the VM is in the TOR switch, and transmitting the Layer 2 frame to the VM.

4. The method according to claim 3 , wherein determining the MAC address comprises: looking up, by the TOR switch, a Layer 2 table according to the Layer 3 destination address, and determines the MAC address; wherein the Layer 2 table indicates at least one of the following: a mapping between a VM IP address and a TOR switch MAC address for a migrated VM and a mapping between a VM IP address and a VM MAC address for a non-migrated VM.

5. The method according to claim 1 , further comprising: receiving, by the top of rack (TOR) switch, an address resolution protocol (ARP) broadcast transmitted by a VM which migrated to the TOR switch; checking, by the TOR switch, a virtual network identifier (VNID) of the ARP broadcast; determining, by the TOR switch, whether the TOR switch is the DN corresponding to the VNID of the ARP broadcast; generating, by the TOR switch, a proxy ARP broadcast with a media access control (MAC) address of the TOR switch, and broadcasting the proxy ARP broadcast along with the VNID, when the TOR switch is not the DN corresponding to the VNID of the ARP broadcast; updating, by the TOR switch, a Layer 2 table, when the TOR switch is the DN corresponding to the VNID of the ARP broadcast.

6. A top of rack (TOR) switch, comprising a processor executing program codes stored in a memory, which configure the TOR switch to: receive a Layer 2 frame carrying a virtual network identifier (VNID); wherein the TOR switch is the designated node (DN) corresponding to the VNID carried in the Layer 2 frame; extract a Layer 3 destination address from the Layer 2 frame; determine whether a virtual machine (VM) corresponding to the L3 destination is in the TOR switch or has migrated; determine another TOR switch to which the VM was migrated, according to the VNID and the Layer 3 destination address, when the VM has migrated, and transmit the Layer 2 frame to the another TOR switch where the VM migrated, when the VM has migrated.

7. The TOR switch according to claim 6 , wherein the another TOR switch to which the VM was migrated is determined by looking up a Layer 2 table according to the Layer 3 destination address, wherein the Layer 2 table indicates at least one of the following: a mapping between a VM Internet Protocol (IP) address and a TOR switch media access control (MAC) address for a migrated VM and a mapping between a VM IP address and a VM MAC address for a non-migrated VM.

8. The TOR switch according to claim 6 , the TOR switch is further configured to: determine the MAC address of the VM, according to the Layer 3 destination address, and transmit the Layer 2 frame to the VM, when the VM is in the TOR switch.

9. The TOR switch according to claim 8 , wherein the MAC address of the VM is determined by looking up a Layer 2 table according to the Layer 3 destination address, wherein the Layer 2 table indicates at least one of the following: a mapping between a VM Internet Protocol (IP) address and a TOR switch media access control (MAC) address for a migrated VM and a mapping between a VM IP address and a VM MAC address for a non-migrated VM.

10. The TOR switch according to claim 6 , the TOR switch is further configured to: receive an address resolution protocol (ARP) broadcast transmitted by a VM which migrated to the TOR switch; determine a virtual network identifier (VNID) of the ARP broadcast; determine whether the TOR switch is the DN corresponding to the VNID of the ARP broadcast or not; generate a proxy ARP broadcast with the a media access control (MAC) address of the TOR and broadcast the proxy ARP broadcast along with the VNID, if the TOR switch is not the DN corresponding to the VNID of the ARP broadcast, and update the Layer 2 table when the TOR switch is the DN corresponding to the VNID of the ARP broadcast.

11. A communication system, comprising: an access switch configured to receive a Layer 3 packet from a remote data center carrying a virtual network identifier (VNID), determine a designated node (DN) corresponding to the VNID, wherein the DN is a top of rack (TOR) switch; generate a Layer 2 frame carrying the VNID according to the Layer 3 packet, and transmit the Layer 2 frame to the TOR switch; and the TOR switch, configured to receive the Layer 2 frame carrying the VNID, extract a Layer 3 destination address from the Layer 2 frame, determine whether a Virtual Machine (VM) corresponding to the Layer 3 destination address is in the TOR switch or the VM has migrated; determine another TOR switch to which the VM was migrated, according to the VNID and the Layer 3 destination address, when the VM has migrated, and transmit the Layer 2 frame to the another TOR switch to which the VM migrated.

12. The system according to claim 11 , wherein the access switch is configured to look up a MAC table according to the VNID, and determine the DN corresponding to the VNID, wherein the MAC table indicates a mapping between the MAC address of the DN and the VNID.

13. The system according to claim 11 , wherein the TOR switch is further configured to look up a Layer 2 table according to the Layer 3 destination address, and determine the another TOR switch to which the VM migrated, wherein the Layer 2 table indicates at least one of the following: a mapping between a VM Internet Protocol (IP) address and a TOR media access control (MAC) address for a migrated VM and a mapping between a VM IP address and a VM MAC address for a non-migrated VM.

14. The system according to claim 13 , wherein the TOR switch is further configured to receive an address resolution protocol (ARP) broadcast transmitted by a VM which migrated to the TOR switch, check a VNID of the ARP broadcast, generate a proxy ARP broadcast carrying the VNID of the ARP broadcast, if the TOR switch is not the DN corresponding to the VNID of the ARP broadcast; and, update the Layer 2 table when the TOR switch is the DN corresponding to the VNID of the ARP broadcast.