6.2 Virtual network overlays and tunneling protocols

Network virtualization takes center stage in SDN environments. Virtual network overlays and tunneling protocols create logical networks on top of physical infrastructure, enabling flexibility and scalability in modern data centers.

These technologies, like VXLAN and NVGRE, allow for network segmentation and multi-tenancy. They use encapsulation to extend Layer 2 networks over Layer 3, supporting up to millions of logical networks and improving resource allocation in cloud environments.

Virtual Network Overlay Protocols

VXLAN and NVGRE: Layer 3 Overlay Solutions

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Top images from around the web for VXLAN and NVGRE: Layer 3 Overlay Solutions

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• VXLAN (Virtual Extensible LAN) extends Layer 2 networks over Layer 3 infrastructure
  • Uses MAC-in-UDP encapsulation
  • Supports up to 16 million logical networks with 24-bit VXLAN Network Identifier (VNI)
  • Operates on UDP port 4789
  • Commonly used in data center environments for network segmentation and isolation
• NVGRE (Network Virtualization using Generic Routing Encapsulation) provides similar functionality to VXLAN
  • Utilizes GRE tunneling protocol with a 24-bit Tenant Network Identifier (TNI)
  • Encapsulates Ethernet frames in IP packets
  • Developed by Microsoft as an alternative to VXLAN
  • Supports multi-tenancy in cloud environments

STT and GRE: Alternative Tunneling Protocols

• STT (Stateless Transport Tunneling) designed for high-performance network virtualization
  • Uses TCP-like header for hardware offload capabilities
  • Supports larger Maximum Transmission Units (MTUs) compared to other protocols
  • Provides better performance in environments with TCP Segmentation Offload (TSO)
• GRE (Generic Routing Encapsulation) serves as a versatile tunneling protocol
  • Encapsulates various network layer protocols (IP, IPv6, IPX)
  • Adds minimal overhead to encapsulated packets
  • Widely supported across different networking devices and platforms
  • Forms the basis for other tunneling protocols (NVGRE)

Network Overlay Concepts

Fundamentals of Network Overlays

• Network Overlay creates a virtual network on top of physical infrastructure
  • Enables logical separation of network services from underlying hardware
  • Supports multi-tenancy and network segmentation in cloud environments
  • Facilitates network agility and flexibility in software-defined networking (SDN)
• Tunneling establishes a virtual point-to-point connection between network nodes
  • Creates a logical path for data transmission across different network segments
  • Enables communication between geographically dispersed sites (VPNs)
  • Supports various protocols (VXLAN, GRE, IPsec) for different use cases

Encapsulation and Decapsulation Processes

• Encapsulation wraps original data packets with additional headers
  • Adds information for routing and identification in overlay networks
  • Preserves original packet integrity while traversing intermediate networks
  • Supports different encapsulation methods based on overlay protocol (MAC-in-UDP for VXLAN)
• Decapsulation reverses the encapsulation process at the destination
  • Removes added headers to reveal original packet contents
  • Performed by network devices or software at overlay network endpoints
  • Ensures proper delivery of encapsulated data to intended recipients

Network Overlay Management

Overlay Network Controller Functions

• Overlay Network Controller centralizes management of virtual network infrastructure
  • Configures and provisions overlay networks across distributed environments
  • Manages virtual network policies, security rules, and traffic flows
  • Integrates with SDN controllers for comprehensive network orchestration
  • Provides APIs for programmatic control and automation of overlay networks
• Controller responsibilities include:
  • Maintaining overlay network topology and endpoint information
  • Coordinating tunnel establishment between network nodes
  • Implementing traffic engineering and load balancing across overlay networks
  • Monitoring overlay network performance and health

Virtual Extensible LAN Implementation and Benefits

• Virtual Extensible LAN (VXLAN) extends Layer 2 domains across Layer 3 boundaries
  • Overcomes limitations of traditional VLANs (4096 VLAN ID limit)
  • Supports up to 16 million logical networks with 24-bit VXLAN Network Identifier
  • Enables workload mobility and flexible resource allocation in data centers
• VXLAN implementation involves:
  • Configuring VXLAN Tunnel End Points (VTEPs) on network devices or hypervisors
  • Defining VXLAN segments and mapping them to VLANs or tenant networks
  • Establishing multicast groups for VXLAN traffic distribution (optional)
  • Integrating with overlay controllers for automated provisioning and management
• Benefits of VXLAN include:
  • Improved network scalability and flexibility in multi-tenant environments
  • Enhanced workload mobility across Layer 3 boundaries
  • Simplified network design and reduced complexity in large-scale deployments
  • Better utilization of network infrastructure through efficient traffic distribution