Design Guide

Design Guide

Figure 5. RSPAN Example

Link Aggregation Protocols

Cisco Fast EtherChannel interfaces and Gigabit EtherChannel interfaces are logically bundled, and they provide link redundancy and scalable bandwidth between network devices. PAgP and LACP help automatically create these channels by exchanging packets between Ethernet interfaces and negotiating a logical connection. PAgP is a Cisco proprietary protocol that can be run only on Cisco switches or on switches manufactured by vendors that are licensed to support PAgP. LACP is a standard protocol that allows Cisco switches to manage Ethernet channels between any switches that conform to the IEEE 802.3ad protocol. Because the Cisco Catalyst Blade Switch 3020 supports both protocols, you can use either IEEE 802.3ad or PAgP to form port channels between Cisco switches.

For both of these protocols, a switch learns the identity of partners capable of supporting either PAgP or LACP and identifies the capabilities of each interface. The switch dynamically groups similarly configured interfaces into a single, logical link, called a channel or aggregate port. The interface grouping is based on hardware, administrative, and port parameter attributes. For example, PAgP groups interface with the same speed, duplex mode, native VLAN, VLAN range, trunking status, and trunking type. After grouping the links into a port channel, PAgP adds the group to the spanning tree as a single switch port.

In Figure 6, each blade switch uses an alternative configuration. The switch is no longer dual homed; instead all the ports are put into a single Cisco EtherChannel uplink to the aggregation switch above. This single EtherChannel uplink can use up to the full 8 ports, providing a 2-to-1 cable reduction from the servers. In this configuration, the Spanning Tree Protocol may not be needed because there is no loop in the network if the interconnect ports between the two blade switches are disabled.

© 2008 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.

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NAD 3020 manual Link Aggregation Protocols, Design Guide . RSPAN Example
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3020 specifications

The NAD 3020 is a classic integrated amplifier that has gained a legendary status among audiophiles since its launch in 1978. Known for its incredible sound quality and value for money, the NAD 3020 has become a reference point in the realm of affordable audio equipment.

One of the main features of the NAD 3020 is its high current design, allowing it to drive a wide range of speaker impedances. This capability ensures that the amplifier can deliver a dynamic sound, characterized by a robust bass response and clear treble. With a power output of 20 watts per channel into 8 ohms, the NAD 3020 is often underestimated due to its modest specifications. However, it can produce remarkable sound pressure levels and handle transient peaks with ease.

The amplifier utilizes a simplified circuit design, which is one of its defining characteristics. This minimalist approach reduces potential signal distortion, enabling the amplifier to maintain sonic integrity. The use of discrete components rather than integrated circuits contributes to its rich, detailed audio reproduction, making it a favorite among purists.

Another key technology featured in the NAD 3020 is its unique power supply design. NAD engineers incorporated a toroidal transformer, which is known for its compact size and low electromagnetic interference. This results in cleaner power delivery, which is essential for maintaining audio clarity and depth.

The NAD 3020 is also equipped with multiple inputs, including phono, line-level, and tape inputs, making it versatile for various audio sources. The built-in phono stage supports moving magnet cartridges, allowing vinyl enthusiasts to connect their turntables directly to the amplifier without needing a separate phono preamplifier.

In terms of build quality, the NAD 3020 features a sturdy chassis that minimizes vibrations, ensuring that audio performance remains stable. The user-friendly design includes a straightforward control layout, allowing users to adjust volume and tone settings with ease.

Throughout its decades-long legacy, the NAD 3020 has influenced countless audio products and remains a benchmark for entry-level amplification. Its combination of power, clarity, and affordability makes it a beloved choice for both new listeners and seasoned audiophiles seeking a dependable amplifier that doesn't compromise on sound quality. The NAD 3020 exemplifies how great engineering can lead to remarkable audio experiences, solidifying its place in the history of hi-fi audio.
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