1. Aled Edwards, Anna Fischer, Antonio Lain HP Labs
Diverter: A New Approach to Networking Within Virtualized Infrastructures
Aled Edwards, Anna Fischer, Antonio Lain HP Labs

2. Outline Data Center Networks for Cloud Computing
Our Approach: Diverter
Evaluation
Future Work
18 September, 2018

3. Data Center Networks for Cloud Computing

4. Data Center Networks for Cloud Computing
Goals (and Challenges!)
Multi-tenancy and Security
Host multiple customers on a single shared infrastructure
Allow each customer to configure their own network topology to suit application needs
Data and performance isolation between customers, and the utility
Allow controlled and efficient inter-communication between customers if required and permitted
“provide rich ecosystem of interacting services”
Large scale
Automation
Flexibility / Programmability
Performance
18 September, 2018

5. Data Center Networks for Cloud Computing
Problems with Traditional Approaches
Traditional L2
Flat network: isolation, scalability
VLANs: configuration, management
Encapsulation, Tunneling
Explicit routing entities required, e.g. routing VMs
Traditional L3
Mobility
Routing bottlenecks
18 September, 2018

6. Our Approach: Diverter

7. Our Approach: Diverter
High-level Overview
Isolate customer resources into Cells
Cell is a collection of virtual resources
Cell has a single owner
Each Cell can have its own virtual network topology
Cells consist of several Subnets
Cell owner can define network policies
Security: define who can communicate with VMs
QoS: define bandwidth limits for VMs
18 September, 2018

8. Our Approach: Diverter
Virtual Network Topology
Subnet C3
Globally managed virtual IP address space representing virtual network topologies
IP address format: 10.<CELL>.<SUBNET>.<HOST> (for example)
Subnet A1
Subnet C2
Subnet B2
Subnet A2
Subnet B1
Subnet C1
Cell A
Cell C
Cell B
Virtual Router
Virtual Router
Virtual Router
18 September, 2018

9. Our Approach: Diverter
Realisation as a Distributed Virtual Router
As virtual routing functionality is distributed across all servers rather than implemented by particular, traditional routing entities,
communication between any endpoints in the infrastructure always involves just a single network “hop”.
Virtual routers are realised as Distributed Virtual Router implementation (“VNET”)
VNET component running on each server
VNET intercepts packets to/from VMs, processes them, eventually forwards them, or discards them
VNET takes care of
Simulating routing across subnets, or Cells
Multicast/broadcast distribution
Address discovery
18 September, 2018

10. Our Approach: Diverter
How Does It Work? MAC Rewriting!
VNET rewrites packets to simulate routing hop
Packets are sent to / received from virtual router interface when crossing subnets
Important to emulate behaviour of traditional network topology
VNET uses (modified) ARP to discover physical machines hosting a particular VM
VNET rewrites packets to send directly to physical machines hosting destination VM
VNET rewrites packets to limit VM broadcast/multicast traffic to particular Cell/subnet
18 September, 2018

11. MAC Rewriting Simplified
1. Packet TX
sVMAC dVMAC
Physical host A
Physical host B
Virtual machines
7. Packet RX
Direct network hop between any endpoint
No virtual MACs leaking onto the physical wire
sVMAC dVMAC
2. Packet
intercept
6. Packet RW
3. Packet RW
4. Packet TX
5. Packet RX
sPMAC dPMAC
sPMAC dPMAC
Physical network
18 September, 2018

12. Virtual Router Simulation
3. Packet TX
sVMAC RVMAC
Physical host A
Physical host B
Virtual machines
9. Packet RX
RVMAC dVMAC
DHCP Response with Virtual Router IP
2. ARP Request / Reply for Router IP
4. Packet
intercept
Virtual MACs do not
leak across subnets!
8. Packet RW
5. Packet RW
6. Packet TX
7. Packet RX
sPMAC dPMAC
sPMAC dPMAC
Physical network
18 September, 2018

13. Our Approach: Diverter
Further Benefits
Efficiency
Use of multicast/unicast ARP instead of broadcast
Local DHCP response generation
No packet encapsulation
Fast tracking of moving VMs/addresses
Security
Integrated network policy framework
Enforcement of fine-grained packet filtering
Allow frequent changes of network policies
Manageability
No programming of physical infrastructure required
No synchronization between physical switches and servers
Only rely on underlying flat L2 network
Separation of concerns: network administrators vs. server administrators
Communication possible with non-VNET servers
No programming of explicit routing entities required
No specific hardware (or hardware modifications) required
18 September, 2018

14. Evaluation

15. Traditional L2 vs. Diverter
Intra-subnet vs. Inter-subnet Communication
Subnet B
Subnet A
Subnet A
Routing VM
Traditional L2
Diverter
Physical network
18 September, 2018

16. Performance Evaluation
VM Network Throughput
18 September, 2018

17. Future Work

18. Future Work Direct Network I/O QoS Virtual Network Cloning
Integrate with virtualization-aware HW on server-side, e.g. SR-IOV NICs, blade server networking
Integration with new I/O virtualization approaches developed around KVM/Xen
QoS
Virtual Network Cloning
Data Center Network Federation
L2 Scalable Data Center Ethernet
18 September, 2018