Class Of Service

High latency networks cause a significant delay when performing file transfer upload or download operations. The degradation is particularly evident on high speed networks. As technology improves, the network bandwidth is getting higher but the laws of physics define the latency. Latency can only be improved minimally.

From a TCP socket application perspective, the simplest way to improve performance is by modifying the TCP sockets IBM i sizes. This is done by setting the sockets SBUFSIZE and RBUFSIZE parameters. This topic describes the mechanism that is followed to set these sizes.

Rather than just setting the buffer sizes, TIBCO MFT Platform Server for IBM i product introduces the concept of Class Of Service (COS). The concept is to set the buffer sizes as well as for other things like limiting the speed of transfers and prioritizing transfers. Initially, Class of Service is used to set the sockets buffer sizes but it can be extended in the future to do more things.

See the following section for the sample Class Of Service Table File (CFCOS), which is distributed with the MFT Platform Server for IBM i.

The format of the COS Table File is:

[Default]

SBUFSIZE = 256000

RBUFSIZE = 256000

[Slow]

SBUFSIZE = 8000

RBUFSIZE = 8000

The value inside the brackets (Default and Slow) are the names of the Class Of Service entries. If a Class Of Service entry name is not defined, the Default Class Of Service entry is used. If the default Class Of Service entry is not used, the buffer values must be set at 256K. This is a good default buffer size that can significantly improve performance in most IBM i system environments. You can update the values in this table file and can add your own Class Of Service entries.

Class Of Service Table File is shipped with MFT Platform Server for IBM i

The default value in the Class Of Service Table File is sufficient for almost all transfers. The only parameter the users may want to change is the Default settings. Users can add new entries to this table or change entries as required. Class Of Service Table File contains records that set the buffer sizes to limit the speed of transfers and prioritize transfers. Class Of Service Table File is used to set the send and receive transfer socket buffer sizes.

Class Of Service Table File is located in the MFT IBM i Platform Server Product Library as a source physical file called (CFCOS) and contains a text member called (CFCOS).

This Class Of Service Table File can be changed by an IBM i text member editor called Source Entry Utility. TIBCO MFT Platform Server for IBM i product does not provide a program to change this table file.

Requests are processed in the order that the COS entries are defined. The first Class Of Service configuration title name entry that matches is selected.

Allowable parameters are:

[Name]: Class Of Service Record Title Entry.

SBUFSIZE: Send Transfer Buffer Size Entry.

RBUFSIZE: Receive Transfer Buffer Size Entry.

This is the same Class Of Service entry records that is contained in the Class Of Service Table File that is distributed with the MFT IBM i Platform Server product.

[Default]

SBUFSIZE = 256000

RBUFSIZE = 256000

[Slow]

SBUFSIZE = 8000

RBUFSIZE = 8000

[Slow1]

SBUFSIZE = 16000

RBUFSIZE = 16000

[Slow2]

SBUFSIZE = 32000

RBUFSIZE = 32000

[Fast]

SBUFSIZE = 128000

RBUFSIZE = 128000

[Fast1]

SBUFSIZE = 256000

RBUFSIZE = 256000

[Fast2]

SBUFSIZE = 512000

RBUFSIZE = 512000

[Fast3]

SBUFSIZE = 1024000

RBUFSIZE = 1024000