1. Data Networking via LANs 10.8- Packets and Frames
By: Marrissa Jones
PHS 221
Fall 2007

2. Translation of a Packet
A packet is a unit of binary data (1s and 0s) that is routed through a computer network.
There are many protocols that use different size packets, they are all arranged into individual bits and bytes into a larger block of data called a data packet.
The data packet is then placed inside a larger container called a frame.
During the transmission, packets are broken down into similar structures and reassembled to the original data once they reach their destination.

3. Frames
A frame is a formation of data packets, which includes layers for easy transmission.
There is a higher-level frame and lower-level frame.
When several layers of protocol are used, each level data will be encapsulated within the next level of the frame.
Perfect Analogy- The use of many envelopes, placed inside each other to create one.

4. Different Types of Frames
Ethernet Frame
IEEE Frame
8 bytes
6 bytes
2 bytes
bytes
4 bytes
Preamble
Destination
Address
Source
Type
DATA
CRC 7
bytes 1
byte
6 bytes
2 bytes
4 bytes
Preamble
Start
Destination
Address
Source
Length
DATA
CRC

5. Walkthrough of a Frame
Preamble- alerts and synchronizes the (NIC) network interface card
Start- Start of the Frame
Destination Address- The MAC (medium access control) address of destination NIC.
Source Address- The MAC address of the source NIC
Length/Type- indicates type and length of data
DATA- carries data being transferred
CRC- cyclic redundancy check on all data, error detection mechanism generated by NIC.

6. Translating Bridge
When a medium using one protocol must connect data to a medium using different protocol, a translator is included in the connection.
Example:
The bridge is used to connect a token-ring LAN to an Ethernet LAN