5.1 Networking Terminology

Since this chapter contains a lot of information about different networking components and their relationships, this section provides a breakdown of some of the networking terminology used here.

  • Port:: the physical network interface on a server. This term is used interchangeably with NIC (Network Interface Card). Network ports can be used to host multiple VLAN interfaces. Multiple network ports can be bonded together for redundancy and performance reasons.

  • Bond: An aggregation of network ports that act as a single network interface for redundancy and performance reasons. Network bonding is also called Data Link Aggregation. Once a port is part of a bond, it can no longer be used outside of the bond. Oracle VM supports a number of different bonding modes or types. A bond can host multiple VLAN interfaces, or be used as an alternative to a physically cabled port.

  • Bridge: A method of conjoining different networks together to act as a single network. This technology is only used when creating Virtual Machine networks, and configuration is handled automatically within Oracle VM. Using bridges, virtual machines on one Oracle VM Server are able to communicate with virtual machines on another Oracle VM Server across a network that has been configured for this purpose.

  • VLAN: A method used to virtualize networking at the switch or router for better control over network separation. VLANs are virtual networks that use identifiers to separate traffic into different networks within the switch. Using VLANs can often reduce network maintenance overhead, as network segregation can be achieved virtually, often from a remote location. Using VLANs can allow servers with a minimal number of physical ports to act as if they were using multiple ports cabled into different networks. Since VLANs can be attached to network bonds, it is possible to achieve the same level of bandwidth that could be achieved using physical cabling by bonding ports together. Although Oracle VM Server can use VLANs, the actual VLAN creation occurs on the switch or router. Network administrators create VLANs and assign VLANs to switch ports on Ethernet switches. The physical cabling from the switch to an Oracle VM Server defines which VLANs are available on the ports or bonds on the Oracle VM Server.

  • VLAN Segments (IDs): VLANs are divided into segments that are usually tagged with an ID. This allows the switch to determine how to direct traffic. VLAN segments can be thought of as separate physical networks. If a VLAN allows untagged traffic, this traffic is all dealt with as if on the same physical network. When creating a logical network within Oracle VM Manager, VLAN segments are attached to the network in the same way that you would attach a port or a bond.

  • VLAN Interfaces: Oracle VM Manager introduces the concept of a VLAN interface. To manage network traffic tagged for different VLAN IDs, a separate virtual interface can be created for each VLAN ID. When creating different logical networks in Oracle VM Manager, these VLAN interfaces can be attached to different networks to specify the type of traffic that belongs to a particular VLAN ID.

  • Logical Network: The networks referred to in Oracle VM Manager are logical networks, in the sense that they do not necessarily represent a single physical network. Since physical components can be bonded together, bridged, or come in the form of multiple VLAN segments using a single port or bond; networks created in Oracle VM Manager are mapped to all of the individual physical or virtual components that make them up. Therefore, creating a network in Oracle VM Manager is a process of aggregating the information about individual network elements that group together into a single logical network. A logical network may incorporate multiple VLANs, physical ports or bonds.

  • Network Channel: Each logical network in Oracle VM Manager can be used for a variety of functional purposes. For performance, security and stability reasons it usually makes sense to separate these functions across different logical networks. Each function is referred to as a network channel. Network channels are used to separate types of traffic to reduce the impact that they have on each other. For instance, cluster heartbeat traffic is very sensitive to latency, while virtual machine traffic should be separated from infrastructure traffic for security reasons. Any number of channels may be attached to a logical network.

  • VNIC: Virtual machines are assigned VNICs or virtual network interface cards, which are allocated faux MAC addresses. This allows each virtual machine to connect to a network. The VNICs are bridged interfaces that are connected to a logical network that has the Virtual Machine channel enabled. A VNIC is only ever assigned to a virtual machine. A virtual machine can have as many VNICs as required within the limitations posed by the virtualization method used. For instance, hardware virtualized virtual machines are able to support a limited number of VNICs, while paravirtualized virtual machines can have an unlimited number of VNICs.

  • Intra-Server Network: It is possible to create a virtual network that exists on a single server and does not connect to any physical interface on that server. A network like this is called an Intra-Server Network and it is usually only used to connect virtual machines running on the server. Virtual Machines that make use of an Intra-Server Network cannot be migrated or moved to another server unless the Intra-Server Network is removed.

  • Hybrid Network: A hybrid network is a network that makes use of VLAN segments for some servers, while making use of physical bonds or ports for other servers within the same network. This is typically done when using heterogeneous hardware where VLANs are used to accommodate multiple networks on a number of servers with a lack of physical ports, or for servers with low priority or bandwidth requirements. In general, it is better to choose one networking methodology to use across your infrastructure for maintenance reasons.