IBM i > Administrator > Networks

How's the Quality of Your Service?

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QoS and iSeries
Now let's focus on what QoS means to you and your iSeries. Figure 1 depicts a fairly typical iSeries configuration. The Los Angeles headquarters is based on an i840. This configuration supports a branch office in New York and connectivity to the public Internet. Although your network probably includes several other traffic types, six typical examples include:

• HTTP traffic from the companys Web server (port 80 or 443).
• FTP file transfers to and from the companys iSeries and PC-based clients (ports 20/21).
• Standard 5250 data stream traffic using Client Access/400 (Telnet port 23).
• Streaming media for training materials or users listening to Internet radio stations.
• Print is still an integral part of most work environments.
• B2B-This sample represents a connection to a supplier or customer with direct Internet-based connectivity (likely VPN based).

If all network traffic is considered equal, you'll have different types of services competing for bandwidth. Unless you have unlimited bandwidth, users will experience choppy or unpredictable response times. This may be particularly noticeable by 5250 users who are accustomed to good, consistent response times. If, for example, you run a large FTP application over the line supporting your 5250 users, you'll notice serious performance degradation of your remote 5250 devices.

While I haven't included all of the possible types of network traffic, I've included enough examples to illustrate that without allocating bandwidth or prioritizing traffic, you'll rapidly lose control over your network and find that response times vary radically depending upon the load and types of network traffic.

Many iSeries shops implement rules banning file transfers during peak periods. Others implement filter rules on their firewalls, blocking streaming media content. While you can try to manage your traffic with business rules and policies, human nature will likely defeat you and you'll no longer be able to deliver the quality of service that your users are accustomed to. You also may find that firewall-based filters and restrictions are filtering out valid business content.

The solution lies in using the built-in iSeries QoS to prioritize traffic or allocate bandwidth to specific applications. QoS is implemented by IP address and port, which means that you can develop rules that prioritize your 5250 applications by creating a rule that sets 5250 traffic (port 23) as your highest priority. You also can provide a high priority for access to your e-commerce Web site. You can assign a priority or allocate bandwidth to each type of application requiring network bandwidth.

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