Priority

(continued)

prioritizes this logical port for intra-nodal traffic; the higher the number, the higher the priority. (This priority has no effect on traffic exiting a node.)

Priorities are configured on all logical interfaces that use a physical frame relay port. The device processor in the node uses these priorities to help determine the order in which it will process protocols.

When configuring priorities, be careful to consider the types of traffic being routed on other connections in the node.

Bandwidth Allocation Group

assigns the logical port to one of sixteen groups whose parameters regulate bandwidth usage by outgoing traffic on the physical link. See "Configuring Bandwidth Allo- cation Groups" on page 7-6.

Encapsulation Method

is the method by which traffic over the logical port will be enveloped within frame relay frames for transmission. The valid methods are T1.617 Annex G and T1.617 RFC1490.

With Annex G, a LAPB frame is encapsulated immediately following the frame relay header (flag, 2-byte T1.618 header, LAPB address, LAPB control, LAPB I-field [x.25/x.75]). With RFC1490, the order is: T1.618 header, Q.922 control byte, Q.933 NLPID, 2-byte level-2 protocol ID, 2-byte level-3 protocol ID, LAPB frame.

Although it may appear that RFC1490 encapsulation uses more overhead, the number of protocols being encapsulated are important in determining the method:

●RFC1490 – The protocols will be identified on the DLCI based on their NLPIDs and (if applicable) level-2 and level-3 headers (e.g., X.25: flag, T1.618 2-byte header, 0x03 Q.922 control, 0x08 Q.933 NLPID, T1.617 level-2 LAPB PID 0x51 81, T1.617 level-3 PID 0x67 80, LAPB frame).

●Annex G – Each protocol must be encapsulated in X.25 for transmission over a single DLCI, because Annex G allows the DLCI to be used only by X.25. Each protocol in would require its own X.25 virtual circuit and level-3 windows.

Modulo

is the number of values used in X.25 level-2 sequenced packets. The actual packet numbering is 0–7 for modulo 8 and 0–127 for modulo 128.

Maximum LAPB Window Size

is the maximum number of sequentially numbered I-frames that can be waiting for acknowledgment by the next station in the path. If this number is exceeded, no frames will be transmitted until an acknowledgment is received. A larger value allows faster throughput, but increases the number of frames that may have to be retransmitted if there is a problem.

N2 Retransmit Count

is the maximum number of times the node will attempt to send an I-frame after a Retransmit Period expiration. A larger value for this parameter increases the proba- bility of an eventual correct transfer between DTE and DCE, but a smaller value permits faster detection of a permanent error condition.

Configuring X.25

8-15

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Cabletron Systems 1800 manual Priority
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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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