CCNA NOTES

• FDDI - Fiber Distributed Data Interface (FDDI) is an appealing choice for high-speed data networking. Essentially, it is a very high-speed token ring network connected by optical fibers. With a data transfer rate of 100Mbps, the ring can support up to 500 nodes with as much as 2 km of spacing between adjacent nodes.
• ATM - ATM stands for Asynchronous Transfer Mode and is a high-speed, packet-switching technique that uses short fixed length packets called cells. ATM can transmit voice, video, and data over a variable-speed LAN and WAN connections at speeds ranging from 1.544Mbps to as high as 622Mbps. ATM is capable of supporting a wide range of traffic types such as voice, video, image and data.
• Frame Relay - Frame relay is a secure, private network that utilizes a logical path or ?virtual circuit? to allocate bandwidth for high performance transmissions. Frame relay is the premier high-speed packet-switching protocol communicating data, imaging, and voice between multiple locations. Frame relay is available in a range of bandwidths from 56 Kbps to full T1 (1.54 Mbps).

TCP

TCP provides connection oriented delivery. TCP requires that a session be established before hosts can exchange data. TCP is a means for building a reliable communication stream on top of the unreliable packet INTERNET PROTOCOL(IP).

TCP is the protocol that support nearly all internet applications.
the sending machine expects an acknowledgment for each packet. If a period elapses without an acknowledgment, it assumes that the information did not arrive and automatically resends it. Incase the packet delivered is damaged a negative acknowledgment NACK is sent. After this packet is resent again.

the other functions are allocating sequence number to each packet transmitted and handling flow control to make sure that the sender does not flood the receiver with packets.

HUBS

A HUB is a small rectangular box includes a series of ports that each accept a network cable. hub joins multiple computers together to form a single network segment. on this segment, all computers can communicate directly with each other.
HUBS are also known as multiport repeaters or concentrators. they connect various segments and acts like a repeater.this enables every segment to receive signals from any other segment.

Loop Avoidance

Redundant links are used to help stop complete network failures if one link fails. Even though redundant links are extremely helpful, they cause more problems than they solve. Because frames can be broadcast down all redundant links simultaneously, network loops can occur, among other problems.
If no loop avoidance schemes are put in place, the switches will flood broadcasts endlessly throughout the internetwork.

A device can receive multiple copies of the same frame since the frame can arrive from different segments at the same time.

One of the biggest problems is multiple loops generating throughout an internetwork. This means that loops can occur within other loops. If a broadcast storm were to then occur, the network would not be able to perform packet switching.