云中网络-TODO

• Network in the cloud

  • Virtualization networkcard

    • Flowchart

    • Share access

      • Connect internally

      • Connect to the outside

        • Network bridging

        • NAT

    • Separation access

  • Overlay network

    • Motivation

    • Definition

    • Approaches

      • GRE - Generic Routing Encapsulation

      • VXLAN

  • SDN

    • Use cases

    • OpenFlow and Openvswitch

  • References

Network in the cloud

Virtualization networkcard

Flowchart

• The steps are shown in the graph below:

  1. Virtual machine could open a char dev file called TUN/TAP.

  2. After opening this file, a virtual network card driver will be seen on the physical machine.

  3. This virtual network card will intercept network packets and send it through TCP/IP.

  4. The virtual network card tap0 will send network packets.

Share access

Connect internally

1. Use the Linux command to create an ethernet bridge

brctl addbr br0

1. Connect two virtual network card to br0

Connect to the outside

Network bridging

• Def: Virtual machine and physical machine will share the same IP address.

• Within cloud, the virtual machines inside Linux also share the same address as physical machines.

• Cons: When there is a large scale of machines, broadcast will be a problem because each virtualized machine needs to be broadcasted.

NAT

• Def: Virtual machines will have different ip address as physical machines.

• A DHCP server will be created for assigning ip addresses to virtual machines dynamically.

Separation access

• Approach: create VLAN based on physical network card eth0

vconfig

• Within the same machine, there is no connectivity between network bridges.

• Across machines, as long as physical bridge support VLAN, there will be no connectivity between different VLANs.

Overlay network

Motivation

• Limitation of VLAN: Only has 12 bits and a capacity of 4096.

• Possible solutions

  • Modify the VLAN protocol.

  • Extend the protocol by adding an additional header.

Definition

• Underlay network: Physical network

• Overlay network: Virtual network implemented on top of underlay network.

Approaches

GRE - Generic Routing Encapsulation

• Idea: It increases the number of VLAN ID by the way of tunnel.

• Example

• Limitation:

  • The number of tunnels

  • It does not support group cast.

VXLAN

• Idea:

SDN

Use cases

• Control and forward

OpenFlow and Openvswitch

• SDN controller administrates the network by OpenFlow protocol.

• Within the Openvswitch, there is a flow table which defines flow rules.

References

• 趣谈网络协议