T1

is the Reply Timer, which is used by the local node to detect a failure by the remote station to send a required acknowledgment or response. The local node will start the timer when it transmits one of these:

●an Information LPDU (LLC protocol data unit).

●a Command LPDU with the P bit set to B'1.' (If this LPDU is sent while the timer is already running, the local node will reset and restart it.)

The node will reset T1 when it receives one of these:

●A REJ (Reject) LPDU, provided a Command LPDU with the P bit set to B'1' is not outstanding.

●A Response LPDU with the F bit set to B '1.'

●An Information or Supervisory LPDU with an NR greater than the last NR received and less than or equal to the line station's VS, provided a Command LPDU with the P bit set to B'1' is not outstanding.

If additional LPDUs are set from the remote station after the local node has reset T1, the timer will be restarted if acknowledgments of or responses to those LPDUs are out- standing. If no acknowledgments/responses are outstanding, the local node will start the inactivity timer. (See "Ti" later.)

If T1 expires and acknowledgments/responses are still outstanding, the local node will send one of the following, then restart T1:

●A Supervisory LPDU with the P bit set to B'1,' to solicit remote link station status.

●Any Unnumbered LPDUs that were not responded to the first time they were sent.

If acknowledgments/responses are still outstanding after N2 tries (see that entry), the local node will declare the link inoperative.

The value specified for T1 should allow for any delays introduced by the MAC sub- layer (e.g., queuing).

T2

is the Receive Acknowledgment Timer, used by the local node to delay sending an acknowledgment of a received Information LPDU. Delaying acknowledgments for as long as possible minimizes the number of acknowledgments that must be sent (since more than one received frame can be acknowledged with one transmission). The timer will be started when the LPDU is received and reset when the acknowledgment is sent. If the timer expires before the acknowledgment is sent, it should be sent as soon as possible.

Ti

is the Inactivity Timer, used by the local node to detect an inoperative condition in either the remote link station or the transmission medium. The timer will be started if T1 has been reset (for one of the reasons listed under "T1" earlier), and additional LPDUs have been sent by the remote link station, and there are no outstanding acknowledgments or responses from the local node.

Configuring SNA

9-23

Page 148 Page 150
Page 149
Image 149
Cabletron Systems 1800 manual Configuring SNA
Page 148 Page 150

1800 specifications

Cabletron Systems, a leading player in network management and telecommunications solutions during the late 20th century, introduced several innovative products that played a crucial role in shaping enterprise networking. Among these were the Cabletron FRX6000, FRX4000, and the FRX1800, which delivered advanced features aimed at enhancing network performance, security, and scalability.

The Cabletron FRX6000 was designed as a robust multi-layer switch, ideal for large-scale enterprise environments. It supported extensive routing capabilities, allowing organizations to manage traffic efficiently even under heavy loads. The FRX6000 boasted high throughput rates and low latency, making it suitable for demanding applications. With support for various network protocols, including IP, IPX, and AppleTalk, its adaptability made it a versatile choice for diverse networking needs. Moreover, security features like VLAN support and Access Control Lists (ACLs) provided enhanced protection against potential threats.

Moving to the FRX4000, this model offered a balance between performance and cost-effectiveness. The FRX4000 maintained many of the essential features of its larger counterpart while catering to medium-sized enterprises. It provided Layer 3 routing and could handle multiple simultaneous connections, ensuring seamless communication across departments. The modular design allowed for easy upgrades, enabling businesses to expand their network infrastructure without significant overhauls. This made the FRX4000 an attractive option for organizations looking to optimize their network investments.

Lastly, the FRX1800, designed for small to medium businesses, focused on simplicity and ease of use while still incorporating powerful network management capabilities. Its user-friendly interface made it accessible for organizations lacking extensive IT resources. The FRX1800 provided essential functionalities such as Integrated Layer 2 switching and routing, network monitoring, and basic security features, ensuring that even smaller companies could maintain efficient, reliable networking without overwhelming complexity.

All three models utilized advanced technologies, including a high bandwidth backbone and state-of-the-art switching architecture, to enable fast and reliable data transfer. They also supported Quality of Service (QoS) mechanisms, allowing businesses to prioritize critical applications and ensure consistent performance across the network.

In summary, the Cabletron FRX6000, FRX4000, and FRX1800 were pivotal in enhancing network capabilities, providing organizations with scalable, secure, and high-performance options tailored to their specific needs.
Top Page Image Contents