TITLE
    ARA 3.0: "AppleTalk Network Not Available" Message
Article ID:
Created:
Modified: 		24549
8/19/98
4/26/00
TOPIC

    I have a Macintosh connected to a Local Area Network (LAN). Periodically I get a message stating "Access to your AppleTalk Network has been interrupted." In some cases AppleTalk services become available again, in other cases the AppleTalk network does not become available again.

    Some segments of the LAN exhibit this problem whereas, other segments never exhibit this problem. Making TCP/IP active or inactive does not seem to make a difference.

DISCUSSION

    There is a known issue with Apple Remote Access 3.0. ARA processes incoming Router Table Maintenance Protocol (RTMP) packets. ARA 3.0 incorrectly processes these packets. On certain networks, this can cause the Macintosh to assume that the network is inaccessible. An alert is posted to notify the user that access to the AppleTalk network has been interrupted. If additional RTMP packets are processed correctly, the network is assumed to be available again.

    This issue is resolved in ARA 3.0.2 and later. ARA 3.0 users may download and install the ARA 3.0.2 Updater to resolve this issue. The Personal Server update is available at http://asu.info.apple.com/swupdates.nsf/artnum/n11436 and the Client update is available at http://asu.info.apple.com/swupdates.nsf/artnum/n11435 .

    ARA Client versions 3.1.2 and later (included with Mac OS 8.5 and later) also contain this fix, so there is no need to update these versions.

    Note: iMac Rev. A (Mac OS 8.1) and PowerBook G3 Series systems that shipped with Mac OS 8.1 use ARA 3.0 as the remote access client. Therefore, customers with these systems may encounter this issue and not realize that it is being caused by Remote Access.

    Newer systems shipping with Mac OS 8.5 include ARA 3.1.2 which has resolved this issue.

    For The Technically Curious

    ARA processes incoming RTMP packets. The RTMP packets consist of tuples that contain network information. Extended network information is contained in 6 byte tuples and non-extended network information is contained in 3 byte tuples. ARA 3.0 maintains a pointer that moves down the list of network tuples.

    The bug description: Instead of moving the pointer by 6 bytes for extended networks, the pointer would only move 3
    bytes. Eventually, ARA would be reading non-valid data which would result in the determination that the network was no longer valid.

    This article can help you locate the software update mentioned here:

Document Information
Product Area: Apple Software; Communications-Networking
Category: Apple Remote Access (ARA)
Sub Category: ARA 3.x

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