Using RFC 1490 to encapsulate SNA

In the previous issue, we discussed the use of DLSw as an encapsulation method for transmitting SNA traffic across your frame relay network. Today, we will address RFC 1490 and some typical methods for prioritizing your SNA traffic.

RFC 1490 is a method for encapsulating different protocols into frame relay. For SNA, this means it can be natively and efficiently encapsulated directly into frame relay. The result is less overhead and more efficient use of frame relay resources than the previously discussed DLSw approach. The Frame Relay Forum worked with the Internet Engineering Task Force and described how this encapsulation takes place in its FRF.3.1 Implementation Agreement.

RFC 1490 is the typical solution for encapsulating SNA, particularly when operating in an SNA-centric network environment. With IBM devices supporting frame relay directly (without, for example, a FRAD), IT managers can maintain more of the look and feel of the traditional SNA network. However, many find that it's cheaper to use a FRAD in front of their FEPs rather than upgrade hardware, especially at host locations. In addition, many users are supporting LAN applications and, therefore, can justify the use of FRADs to handle the multi-application environment.

Because of its mission-critical nature, SNA often requires prioritization over existing applications, which could negatively impact response times and possibly cause session failures. The following are three methods often used to prioritize SNA traffic:

• Via CPE, assign a higher priority to sending SNA traffic over LAN IP/IPX traffic when both applications are traversing the same PVC.
• Use separate PVCs for each application, and use CIR assignment to allocate bandwidth dynamically to each.
• Also through CPE, allocate more bandwidth by percentage to SNA than LAN IP/IPX utilizing the same PVC.

TeleChoice is one of the leading telecommunications consultancies worldwide for the design, development, implementation, and migration of new and leading edge telecommunications hardware, software and services. Our focus is on public networking and value-added services for the telecommunications industry. You can contact TeleChoice at its corporate headquarters at (973) 239-0700 or visit our Web site for more information.

The benefits and drawbacks of DLSw
The newsletter referred to at left.

Transporting SNA Traffic over Frame Relay
RFC 1490 versus Data Link Switching.

Multiprotocol Interconnect over Frame Relay
RFC 1490.

Configuring SNA Frame Relay Access Support
Documentation from Cisco.

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