# CCNA: Topics not covered by ICRC courseware, by John & Stephen.

#

# Switching

Cut-through When a packet enters the switch its destination address is read and the leading edge of the packet is forwarded through the output port before the entire packet finishes entering the input port.

· Faster than Store and Forward (Low Latency)

· Bad packets may be forwarded

Store and Forward When a packet enters the switch it is completely read into the switch, the cyclic redundancy check (CRC) is run, and it is forwarded out the appropriate output port.

· Latency varies depending on frame size

· Bad packets are dropped

· Default setting on Catalyst 5000 Switches

Spanning Tree Protocol Implemented to eliminate loops on a switched network.

· Uses the Spanning Tree Algorithm (SPA)

· IEEE specification is 802.1d

### ISDN

BRI Basic Rate Interface. Can carry voice, data, and video.

· 2B + 1D

· B channels have a bandwidth of 64 KBPS and are used for transmitting.

· D channel has a bandwidth of 16 KBPS is used for signaling

PRI Primary Rate Interface. Can carry voice, data, and video.

· US and Japan - 24B + 1D , 1.544 MBPS

· Europe and other parts of world - 30B + 1 D, 2.048 MBPS

· B channels have a bandwidth of 64 KBPS and are used for transmitting.

· D channel has a bandwidth of 64 KBPS is used for signaling

## ISDN Protocol Prefixes

E ISDN integration with existing telephone networks

Q ISDN Switching and Signaling

I ISDN Concepts, Terminology and Services

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