FAQ

1. What is layer-2 switch ?

A: If the switching process is carried out based on MAC address in Ethernet packets, the switch is called a

layer-2 switch.

2. What is the difference between Intelligent Switch and dummy switch ?

A: Dummy switch is a simple switch. It just transfers packets between connections. It can not control and monitor

traffic in the switch. Intelligent Switch is a switch with lots of software function. It can help the network administrator

to configure and manage network.

3. What is VLAN ? Does NETSYS' Intelligent Switch support overlapped VLAN ?

A: VLAN is Virtual LAN. A Virtual LAN is a collection of network nodes that share the same collision domain

regardless of their physical location or connection point in the network. A VLAN serves as a logical workgroup with

allowing users to share information and resources as though located on the same LAN. Because there is a PVID no

physical barriers, number to assign the VLAN action of each connection port, NETSYS' Intelligent Switch supports

overlapped VLAN.

4. What is the difference between In-Band Management and Out-Band Management ?

A: If the management of the network is from a station attached directly to the network, it is In-Band Management.

Console management interface is In-Band Management. If the management of the network is from a station

not attached to the network, it is Out-Band Management. Telnet and Web-Browser management interface are

Out-Band Management.

5. Does NETSYS' Intelligent Switch support QoS function ?

A: If there is priority information in the tag of Ethernet packet, NETSYS' Intelligent Switch will read the priority

information and put the packet to some queue according to the priority. There are 4 queues for every port. The

QoS (Quality of Service) function is carried out with this function.

6. What is Spanning Tree Protocol ? Does NETSYS' Intelligent Switch support it ?

A: Spanning Tree Protocol is a technology that checks your network for any loop. A loop can often occur in

complicated or back- up linked network systems. Spanning-tree detects and directs data along the shortest path,

maximizing the performance and efficiency of the network. NETSYS' Intelligent Switch supports this function.

7. What is packet buffer ? Will it affect the performance of a switch ?

A: Because NETSYS' switches are designed with store-and-forward algorithm, these switches need a buffer to

store the incoming packet and the buffer is called packet buffer. If the operation of the switching controller is

very high efficient.

8. Is 1 Mbps for HomePNA fast enough ?

A: 1 Mbps data transfer rate is nearly 18 times faster than standard 56k modem connections, and provides ample

bandwidth for nearly all of the current user requirements for a home networking solution. As next-generation

applications begin to be deployed that take advantage of home networking capabilities, additional bandwidth will be

required to support the real-time transfer of audio, video and data.

9.What are the technical aspects of the 1 Mbps HomePNA physical layer technology ?

A: The HomePNA has chosen to standardize on a technology available now from Tut Systems, allowing consumers

to link devices at speeds up to 1 Mbps over existing home phonelines. The technology supports the complex,

random-tree type of wiring typically found in the home and does not require any hubs or new Category 5 wiring.

The HomePNA network requires no special terminations, filters or splitters. It uses only the single pair of existing

phone wires to make its connection, and operates concurrently with any normal telephone service that might be

using those same wires. The technology also coexists with the new splitterless Universal ADSL standard. It is fully

compatible with the Ethernet MAC layer standard (IEEE 802.3 CSMA/CD with a new physical layer) and meets

applicable FCC regulatory requirements

10.Has NETSYS' tested this technology to ensure it works in homes ?

A: NETSYS' device is fully compliant with the initial 1 Mbps technology specification adopted by the HomePNA.

The HomePNA data technology has undergone two rounds of significant testing in hundreds of homes located

throughout the United States. The latest indicates that 99% of the tested homes can accommodate Phoneline-

networking solutions.

11.What is the Home Phoneline Networking Alliance ?

A: The Home Phoneline Networking Alliance (HomePNA) is an association of industry-leading companies working

together to ensure adoption of a single, unified phoneline networking standard. Founding companies include AMD,

Compaq, IBM, Hewlett Packard, Tut Systems, 3Com, and Epigram among others.

12.Why is phoneline important ?

A: Any home networking solution must fulfill three key requirements. It should not require the installation of

new wiring, and must be both inexpensive and easy-to-use. Very few end-users are willing to run new wiring

throughout their home to network multiple devices. Phone wiring provides a near ubiquitous solution for this

no new wires requirement, providing distributed network access points at key locations throughout a home.

Phone wiring is also a very secure transfer medium since internal wiring is connected back directly through

the local loop to a central office.

13.Does this new technology interfere with standard telephone services ?

A: No. All Home Phoneline Networking Alliance (HomePNA) devices use a technology called Frequency Division

Multiplexing (FDM) that enables multiple services to use the same set of wires simultaneously without impacting

one another. The HomePNA technology can also operate simultaneously with the new UADSL technology that

delivers over 1 Mbps of bandwidth to the homevia telephone wires

14.How does home phoneline networking work? Will it require any special equipment ?

A: The HomePNA is committed to the concept of a "no new wires" networking technology that is simple to install

and maintain. NETSYS has develop a Ethernet-compatible control that enables a LAN over the complex,

random-tree wiring found in nearly all homes. The technology does not require any hubs, routers, splitters, filters,

terminations or any other special equipment.

15.What is RMON and do NETSYS' switches support RMON ?

A: The Remote Monitoring (RMON) is a tool used by network managers to monitor remote devices. An RMON

implementation consists of a software agent that continually collects statistics about a LAN and a management

station that communicates with the agent.The agent transfers information to the management station on

request or when a predefined threshold is crossed. RMON is a standard for traffic analysis and troubleshooting,

especially for switched networks. It defines specifications for monitoring network traffic above the MAC layer.

Network administrators can deploy standards-based diagnostic solutions for enterprise-wide traffic and

support mission-critical, server-based applications. We have support this standard.

16.What is the difference between "cut-through" and "store-and-forward" ?

A: Cut-Through: The switch will begin forwarding data after it receives the DA (destination address) of the

frame, the difference between this and store-and-forward is that store-and-forward receives the whole

frame before forwarding. Since frame errors cannot be detected by reading only the DA, cut-through may

impact network performance by forwarding corrupted or truncated frames. These "bad" frames can create

broadcast storms wherein several devices on the network respond to the corrupted frames simultaneously.

Advantages of Cut-Through:+ Cut-Through is faster because the packet is sent as soon as the first eight

bytes are received.+ Cut-Through requires less memory since the switch only reads the address but does

not store the entire message. Disadvantages of Cut-Through:+ Bad packets are perpetuated, taking up

bandwidth.+ Benefits diminish in the high trafficnetworks.+ Cut-Through cannot be used on networks that

use both Ethernet and Fast Ethernet. The network must be one or the other. Store-and-Forward: The switch

will wait until the entire frame has arrived prior to forwarding it. This process ensures that the destination

network is not affected by corrupted or truncated frames, but is a slower method than cut-through. Advantages

of Store-and-Forward: + Store-and-forward only sends out valid data packets. Bad packets created by

collisions on the network or other problems are not sent.+ Use Store-and-Forward when some devices on

the network run at 10Mbps and other run at100Mbps. Disadvantages of Store-and-Forward: + Store-and

-Forward requires more time because it receives the whole packet before sending it out. Every byte

buffered is an additional 8 micro-seconds of delay.+ More memory is required to store the data packet

before sending it out.

17.What is collision domain ?

A: Defined by IEEE 802.3 Standard: A single CSMA/CD network. If two or more MACs are within the same

collision domain and both transmit at the same time, a collision will occur. MACs separated by a repeater

are within the same collision domain. MACs separated by a bridge are within different collision domains.

18.What is Flow Control regarding of all switches ?

A: During times of heavy network activity, the switch's port buffers can receive too much traffic and fill up faster

than the switch can send the information. In cases like this, the switch tells the transmitting device to wait so the

information in the buffer can be sent. This intervention is called flow control. The method of flow control depends

on whether the ports are set to full- or half-duplex. A non-standard but popular scheme called Back-pressure

was used in half-duplex links. The IEEE 802.3 committee established a standard called 802.3x flow control was

used in full-duplex links.

19.What kind of security of switches provide or support ?

A: There are two ways to use a switch to improve network security: VLAN: A network administrator can

define several VLANs and block access to each VLAN to prevent users from accessing servers for which they

don't have access permission. Mac address filtering: A network administrator can define a DA (Destination Address)

so that packets can only be received from port A (a hub) and only allow those same packets to be forwarded to

port B(a server connection, for example).Using MAC address filtering, only users that are connected to port A can

access the server connected to port B, other packets from other ports, even those whose DA is for the server

on port B, will be dropped