Lecture 3 Virtualization¶

今天的主题是：网络虚拟化

Introduction¶

In fact, it's a common situation that sometimes we have to divide a single broadcast domain into multiple broadcast domains
Therefore, we can utilize Virtual LAN to solve this problem

Virtual LAN¶

A VLAN logically identifies a set of ports attached to one (or more) Ethernet switches, forming one broadcast domain

Some Problems We Met¶

We attach an example related to the VLAN image above.

Here we meet a serious problem:

VLAN ID¶

VLAN ID: from 0-4095, with 0 and 4095 being reserved

The message is only sent to the specified port (in the same category)

Datacenter Network¶

Compute Virtualization¶

Structure of VM¶

Connection between VMs¶

Problem - Limited VM Migration Scope¶

Situation¶

VLAN limits the VM migration scope

Supplementary Materials:

VM Migration

In the context of virtualization, where a guest simulation of an entire computer is actually merely a software virtual machine (VM) running on a host computer under a hypervisor, migration (also known as teleportation,[1] also known as live migration) is the process by which a running virtual machine is moved from one physical host to another, with little or no disruption in service.

Reason - Small Number of VLANs¶

Solutions for DCN¶

Build a Large Layer 2 Switch¶

Common Sense

When a server is migrated from one port of a Layer 2 switch to another port, its IP address can remain unchanged

Build Overlay¶

=> Build an overlay network with tunnels

The detailed solution is VXLAN, which will be introduced next.

VXLAN¶

VXLAN: Virtual Extensible LAN
- network virtualization over Layer 3 (NVO3)
Structures:
- VM / VTEP / VXLAN tunnel
Introduction:
- VTEP: Virtual Tunnel End Point
- VM: Virtual Machine
- VXLAN: Virtual Extensible LAN