● An Information or Supervisory LPDU with an N(R ) greater than the last N(R )

received and less than or equal to the line station's V( ), provided a Command

S

LPDU with P bit set to B'1' is not outstanding.

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

If T1 expires and acknowledgments/responses are still outstanding, the link station 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 "N2"), the link station 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 Receiver Acknowledgment Timer, used by the link station to delay sending an acknowledgment of a received Information LPDU. The timer is started when the LPDU is received and reset when the acknowledgment is sent. If the timer expires before the acknowledgment is sent, it must be sent as soon as possible.

Ti

is the Inactivity Timer, used by the link station 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"), and additional LPDUs have been sent by the remote link station, and there are no outstanding acknowledg- ments or responses from the local link station.

If the local station does not receive an LPDU before Ti expires, the station must send an LPDU with the P bit set to B'1' to solicit the remote station's status. Recovery then proceeds as described under "T1."

N3

is the number of Information LPDUs that will be received before sending an acknowl- edgment . This parameter is used in conjunction with T2 to allow stations to reduce traffic. A counter is initialized to N3, and will be decremented by one each time a valid sequential Information LPDU is received. When the counter reaches 0 an acknowl- edgment is sent.

N3 is reset whenever an Information or Supervisory acknowledgment LPDU is sent by the local station.

Tw

is the maximum number of sequentially numbered Information LPDUs that the link station can have outstanding.

N2

is the maximum number of times that an LPDU (including Information LPDUs resent after a checkpoint operation) will be sent following expiration of T1.

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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.
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