Frames Packets and PDU's
There can be confusion about Frames, Packets and other subsets of network communication.
A frame can be defined as the unit of data transferred across the network, defined at the datalink (network access) layer of the protocol stack.
A packet can be defined as the unit of data at any layer of the protocol stack, prior to, or after transmission.
Application layer is called a message.
Transport layer data is sometimes referred to as TCP or UDP segments. Layer 4
Internet layer, data is sometimes talked of in terms of IP, ARP and RARP datagrams. Layer 3
The datalink layer data is referred to as frames. Layer 2
Physical layer, data is sometimes referred to as bits. Layer 1
Frames simply encapsulate the data with a header and addressing information. In ethernet networks the source and destination adress are defined by the MAC. MAC or Media Access Control address is a hardware address that uniquely identifies each node of a network.
In computer networking, "encapsulation" is to include data from an upper layer protocol into a lower layer protocol.
In telecommunication, encapsulation is the inclusion of one data structure within another structure so that the first data structure is hidden for the time being. For example, a TCP/IP-formatted data packet can be encapsulated within an ATM frame (another kind of transmitted data unit). Within the context of transmitting and receiving the ATM frame, the encapsulated packet is simply a stream of bits beween the ATM data that describes the transfer.
As data descends the source protocol stack, successive levels encapsulate the data with additional information. After a frame has been received at its destination, successive layers then de-encapsulate the data as it travels up the destination protocol stack.
Therefore, a packet can be discussed in terms of its subsets - messages, segments and datagrams.
Some good links to review on this are below:
Encapsulation:
Encapsulation
Frames and Packets:
Ethernet Frames and Packets
Packets inside Frames or Frames inside Packets
Frames, Packets, Datagrams and PDU's
A frame can be defined as the unit of data transferred across the network, defined at the datalink (network access) layer of the protocol stack.
A packet can be defined as the unit of data at any layer of the protocol stack, prior to, or after transmission.
Application layer is called a message.
Transport layer data is sometimes referred to as TCP or UDP segments. Layer 4
Internet layer, data is sometimes talked of in terms of IP, ARP and RARP datagrams. Layer 3
The datalink layer data is referred to as frames. Layer 2
Physical layer, data is sometimes referred to as bits. Layer 1
Frames simply encapsulate the data with a header and addressing information. In ethernet networks the source and destination adress are defined by the MAC. MAC or Media Access Control address is a hardware address that uniquely identifies each node of a network.
In computer networking, "encapsulation" is to include data from an upper layer protocol into a lower layer protocol.
In telecommunication, encapsulation is the inclusion of one data structure within another structure so that the first data structure is hidden for the time being. For example, a TCP/IP-formatted data packet can be encapsulated within an ATM frame (another kind of transmitted data unit). Within the context of transmitting and receiving the ATM frame, the encapsulated packet is simply a stream of bits beween the ATM data that describes the transfer.
As data descends the source protocol stack, successive levels encapsulate the data with additional information. After a frame has been received at its destination, successive layers then de-encapsulate the data as it travels up the destination protocol stack.
Therefore, a packet can be discussed in terms of its subsets - messages, segments and datagrams.
Some good links to review on this are below:
Encapsulation:
Encapsulation
Frames and Packets:
Ethernet Frames and Packets
Packets inside Frames or Frames inside Packets
Frames, Packets, Datagrams and PDU's
posted by Bruce Warner @ 9:41 AM
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