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NFV Nuts & Bolts: NIC bonding - a must have for Carrier Grade OpenStack™


Author: Sarbajit Chatterjee: Solution Architect – SDN & Network Virtualization, NFV BU


For carriers today, IT transformation means making the journey to the cloud, and OpenStack has quickly proven itself the de facto cloud environment. But the reality is, as a communications service provider you must overcome real hurdles as you virtualize your infrastructure during your journey to the cloud. Enterprise IT cloud solutions simply were not designed to meet your gold standard for fault tolerance and performance.


But that’s changing fast. The HP OpenNFV platform is one of the leading industry initiatives for carrier-grade cloud.


While there are many facets to achieving a carrier-grade cloud, an important step is to use NIC (network interface card) bonding or link aggregation to achieve necessary levels of resiliency and performance. With NIC bonding, multiple NICs in the server are teamed to increase the throughput and fault tolerance if a link fails.


Why you need NIC bonding


The high-density workloads in a carrier-grade cloud require high network throughput, and a single NIC in an off-the-shelf server may not provide sufficient throughput. Having an ultra-high-throughput NIC in a server may be unrealistic, but most servers come with multiple NICs. Bonding these NICs can provide higher network throughput for your carrier-grade cloud.


NIC bonding also delivers the resiliency demanded by telecom workloads. If one of the bonded NICs goes down or loses the link, then the other NICs present in the bond can carry the traffic and provide an uninterrupted operation.


All major operating systems, including Linux, support NIC bonding. Some bonding modes require support from the connected switch, and the HP 5900 Switch Series is an ideal option for these deployments.





Understanding NIC bonding modes


You can choose among multiple modes for NIC bonding, depending on your needs. At the most basic level, there is switch-dependent mode and switch-independent mode. Switch-dependent mode requires configuration changes in the switch that is connected to the server’s NIC ports. The IEEE 802.3ad Link Aggregation Control Protocol (LACP) mode of bonding is an example of switch-dependent bonding. The switch-independent mode of bonding doesn’t need to be configured in the switch. Active-backup mode is an example of this mode.


OpenNFV can use multiple Linux bonding modes:

  • Round robin (balance-rr): Round robin is the default bonding mode and it provides sequentially ordered packet transmission through the slave NICs. It is fault tolerant and load balanced.
  • Balance-XOR: This mode uses an algorithm that accounts for source MAC and destination MAC to determine which slave NIC to use. The slave NIC always remains same for same source and destination MAC.
  • Active-Backup: Only one slave NIC is active at a time, and load balancing is not supported. If the active NIC goes down, only then will the other slave NIC become active.
  • Dynamic link aggregation (LACP): The aggregation group is created with same duplex configuration. LACP is driven by IEEE 802.3ad specifications. This mode requires changes in the switch.
  • Broadcast: This mode transmits packets out of all slave NICs.
  • Balance-tlb: The packets are transmitted out of all the slaves so the load is balanced; however, only one slave NIC is designated to receive packets. Changes in the switch are not required.
  • Balance-alb: This mode is similar to balance-slb mode, but the receiving is also load balanced. Linux uses ARP negotiation to achieve receiver load balancing.

Linux provides ifenslave utility to configure NIC bonding.


NIC bonding in OpenStack can be achieved using Open vSwitch (OVS). OVS supports three NIC bonding modes: active-backup, balance-tcp, and balance-slb. Using OVS bonding with OpenStack is more configurable, because it is the default vSwitch software used with controller and compute nodes. Using a vSwitch-based approach eliminates the need for using the host-level bonding configurations while providing similar results.


NIC bonding is just one way that HP is building carrier-grade NFV solutions to deliver enhanced performance and fault tolerance for your cloud services. To learn more about how HP can help you with your journey to the cloud, please explore our NFV resources and solutions for CSPs.  


"The OpenStack™ Word Mark and OpenStack Logo are either registered trademarks/service marks or trademarks/service marks of the OpenStack Foundaiton, in the United States and other countries and are used with the OpenStack Foundation's permission. We are not affiliated with, endorsed or sponsored by the OpenStack Foundation, or the OpenStack community."
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