Competition for network virtualization technology of four major hosts in the data center

Competition for network virtualization technology of four major hosts in the data center

Since it is the virtualization of the host network, it is actually the virtualization of network functions on the server. Server vendors who propose such technologies hope to use this technology to expand the influence of servers in data centers and weaken the functions of network devices.

When talking about virtualization, we must first think of VMware, a manufacturer specializing in host, especially the research of server virtualization technology. VMware has long monopolized the market of host virtualization technology. It once held a market share of up to 90%. With the entry of other software manufacturers, its share has gradually declined, but it is still the leader in virtualization technology. Today's virtualization technology is no longer limited to the virtualization of server operating systems, including application software, network, and storage, it can be said that virtualization technology has gradually penetrated into every technical field of the data center. In addition to servers, VMware's virtualization in the network, storage, security and other fields is not a strong point. A number of new virtualization vendors have emerged, which makes the virtualization market full of competition, some traditional IT giants have joined the competition. This article is about a classification of virtualization technology: host network virtualization technology, that is, network virtualization through server hosts, which may be confusing. As we all know, servers all have NICs and some simple route forwarding table items can be configured. server vendors hope to optimize the server network functions to achieve network virtualization.

Since it is the virtualization of the host network, it is actually the virtualization of network functions on the server. Server vendors who propose such technologies hope to use this technology to expand the influence of servers in data centers and weaken the functions of network devices. Of course, network equipment vendors will not agree, and network vendors also have their own virtualization technology, highlighting the implementation of hardware. hardware-based virtualization, in contrast, the host network virtualization technology is relatively soft. In this way, the host network virtualization technology is flexible, but the forwarding efficiency is low, while the network vendor virtualization is highly efficient, but not flexible enough, more depends on the hardware technology level. In any case, the host network virtualization technology will exist for a long time as a virtualization technology. The following describes the four major technical features of the host network virtualization technology.

VXLAN

VXLAN (Virtual Extensible LAN) is a network Virtualization Technology proposed by companies such as Cisco, VMware, Citrix, and Broadcom. These companies are currently the most powerful combinations in the network and virtualization fields, VXLAN is currently the most comprehensive and practical technology. VXLAN is a tunnel forwarding mode that encapsulates Ethernet packets on the UDP Transport layer. The destination UDP port number is 4798, and the layer-2 network segment is identified by 24 bits, VXLAN can deploy millions of virtual networks in a data center. VXLAN encapsulates network traffic such as unknown unicast, broadcast, and multicast as multicast forwarding. The physical network must support any source multicast. VXLAN data packet format is easy to implement in hardware, so it can be more closely integrated with physical network devices in the future, using the features of high hardware forwarding efficiency, VXLAN is implemented through hardware. VXLAN is widely recognized by data centers and is currently the most popular network virtualization technology, because it uses the existing universal UDP transmission with the highest maturity.

DOVE

DOVE (Distributed Overlay Virtual Ethernet) is a Distributed covered Virtual Ethernet technology proposed by IBM. It will allow engineers to abstract physical network infrastructure from management program hosts, in this way, they can change the network in the software, instead of the hardware. When virtual machines are migrated between the data center and the data center, these network instances can better manage and support virtual machines. DOVE deployment is supported in IBM DVS5000V products. The Protocol definition of DOVE is almost the same as that of VXLAN, which allows DOVE to support the underlying network hardware of any VXLAN. Unlike VXLAN, DOVE does not require physical infrastructure multicast when creating a coverage, but VXLAN does. No one in the data center is willing to use multicast because it affects network performance. DOVE can be used in vSphere, KVM, and Hyper-V. Now IBM has sold low-end servers to Lenovo, And the chip business also wants to change. In this context, the future prospects of DOVE are not very clear, without the advantages of the traditional market of IBM servers, it is difficult for DOVE to be widely used.

NVGRE

NVGRE is a General Routing Encapsulation standard proposal submitted to IETF by Microsoft, Intel, Dell, and HP. NVGRE supports 1.6 million networks by defining a 24-bit lease network identifier. NVGRE uses GRE to create an independent virtual L2 network, limiting the physical L2 network or extending beyond the subnet boundary. NVGRE requires physical network devices to recognize the extended information of the GRE tunnel. Unknown unicast, broadcast, multicast, and other network traffic are encapsulated as multicast forwarding. RFC 2784 and RFC 2890 describe the NVGRE implementation standards in detail. Compared with VXLAN, NVGRE does not explain in detail how the data packet is obtained through the channel to find the target terminal. There is no clear description of the VXLAN standard.

STT

STT (Stateless Transport Tunneling) is a host network Virtualization Technology proposed by VMware. STT uses the TCP Data encapsulation mode, but modifies the TCP transmission mechanism. Data Transmission does not follow the TCP state machine, but is a completely new stateless mechanism. It does not need three handshakes to establish TCP connections, currently, it has been implemented in vSwitch. The STT uses 64 bits to identify L2 network segments. The STT endpoint needs to reserve a TCP Port for STT. All TCP packets sent to this Port will be considered as STT packets and will not go through the normal TCP path.

The above four host network Virtualization Technologies share a common feature: they all perform secondary encapsulation on the basis of Layer 2. the difference lies in the difference in the encapsulation mode and length. VXLAN and DOVE are both based on UDP encapsulation, NVGRE is based on GRE encapsulation, and STT is based on TCP encapsulation. Only UDP is the most acceptable method. In addition to the DOVE method, the other three methods are implemented through multicast, and the forwarding efficiency is not as high as that of DOVE. However, because DOVE is the exclusive and intensive of IBM, it is only implemented on its own device, the compatibility is not very good, so it is not paid enough attention. No matter which virtualization technology is used, the objective is to expand the scope of the L2 network. The traditional L2 VLAN only has 4094 identifiers, which cannot meet the deployment requirements of data center services, therefore, these host network Virtualization Technologies have emerged. For some small and medium networks, there is no need to use such technologies. Traditional VLAN technology is still enough and is not outdated. In the future, these four technologies will be constantly modified and improved. Although VXLAN is leading the way for the moment, it is still unknown who can reach the end first. Let's wait and see.