Maximum Retransmissions

is the maximum number of times the port will attempt to send a frame if the PU is not responding. A larger value increases the probability of an eventual correct transfer between DTE and DCE, but a smaller value permits faster detection of a permanent error condition.

Outstanding Frames

also called level 2 window size, is the maximum number of sequentially numbered frames that can be waiting for acknowledgment. If this number is exceeded, no more frames will be transmitted until an acknowledgment is received. A larger value allows faster throughput.

Note that this parameter can be changed without disabling the link, except if the existing value is within the range 0–7and the new value is greater than 7. (0–7is modulus 8 or 128; anything greater is only modulus 128. Changing the modulus will disable the link.)

Generate Clock

specifies whether the port will generate the clock necessary to synchronize traffic over the link. If the port is a physical DCE (determined by the port's I/O cable interface), configure Generate Clock as Y, since the physical DCE generates clock. If the port is DTE, configure Generate Clock as N.

Rcv Clock (TT) from DTE

allows the clock to be looped back from the DTE using the TT (Terminal Timing) signal, which can be helpful on high-speed lines. Generally, if the local interface is physical DCE and the line speed is above 256 Kbps, this parameter should be set to Y. (Make sure the remote DTE is configured to provide the terminal timing.)

SNA Type

0 = XPAD, 1 = TPAD, 2 = HPAD, 3 = NPAD. Pressing [L] at the Port screen changes the value to the next one in the list.

The most common SNA networking requirement is for communication between an SNA host computer (PU type 4) and control units (PU type 2). This is accomplished via an HPAD (Host PAD) and TPAD (Terminal PAD). The host computer FEP is con- nected to the HPAD and the cluster controller is connected to a TPAD.

The XPAD is particularly useful for networking of statistical multiplexers and other bit-sync devices.

NRZ

determines the level of data encoding:

Y = NRZ (Non-Return to Zero) on, which means that 1 represents high-level encoding and 0 is low-level.

N = NRZ off, which means that 1 represents no change in level and 0 is a change.

Unless there is a site-specific configuration needing NRZI (Non-Return to Zero Inverted), always use NRZ for all SNA modes. (NRZ off = NRZI on.)

Packet Size

is the maximum packet size that will be transmitted on the port.

Configuring SNA

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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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