Anticipates: VLANs, SNMP, reliability/fault management, measurements/performance management
in- vs out-of-band issues 1
Depicts two alternatives of network that is shared by both management and production traffic (in-band management ) , which keeps management and production of network physically separated (out-of-band management). Which option makes the most sense? The answer is, it depends. Like so much in engineering, it is all about trade-off.
- The capital of out-of-band management contains a dedicated management channel to maintain devices, which in-band management doesn't need to consider. It needs a system administrator to remotely control and monitor the management servers and other network equipments anytime, which in-band management monitors the channel only when operating systems being booted. Hence the expense of out-of-band management seems larger than in-band management.
- —Data information and management information are transmitted together in-band management , while they prefer to be transmitted through separate network connections under out-of-band management. Information being transmitted under out-of-band management has better reliability since it is possible for NM interfaces to continue working even data interface fails. Meanwhile the issue of out-of-band management is that the number of failure points may increase with the increment of NM interfaces.
- —As we know, NM frame is small and is transmitted bursty. Based on its characters, in-band management is hard to control the loading if data frames and NM frames transmit through the same interface. When NM download large files or update softwares to statistic the configuration figures, the amount of NM frames is sufficient to interfere with other applications and traffic delay may out of control. What is worse, NM will be noticed by bad traffic and generate more frames. The solution is separating traffic class by priorities or Vlan, not small NM frames transmitting firstly. Out-of-band management, transmitting data and NM frames in separating subchannel,does not exist these kind of problems.
Note that although out-of-band management spend more money on hardware, in-band management needs software and TP/IP protocol for SNMP to make devices support all the layers and does not allow access to BIOS setting or remotely reinstall the system. Choosing alternatives of two management methods depends on the specific situation. Meanwhile,out-of-band management has better performance in reliability and interference.