?– A ?¬?xed window is a window with an unchanging size that can accommodate a speci?¬?c
?¬‚ow of segments.
?– A TCP sliding window is a window that can change size dynamically to accommodate
the ?¬‚ow of segments.
?– TCP provides the sequencing of segments by providing sequence numbers and
acknowledgment numbers in the TCP headers.
Exploring the Packet Delivery Process
The previous sections discussed the elements that govern host-to-host communications.
You also need to understand how these elements interact. This section covers host-to-host
communications by providing a graphic representation.
Layer 1 Devices and Their Functions
Layer 1 de?¬?nes the electrical, mechanical, procedural, and functional speci?¬?cations for
activating, maintaining, and deactivating the physical link between end systems. Some
common examples are Ethernet segments and serial links like Frame Relay and T1.
Exploring the Packet Delivery Process 85
Repeaters that provide signal ampli?¬?cation are also considered Layer 1 devices.
Figure 1-56 shows some common Layer 1 devices.
Figure 1-56 Layer 1 Devices
The physical interface on the NIC can also be considered part of Layer 1.
Layer 2 Devices and Their Functions
Layer 2 de?¬?nes how data is formatted for transmission and how access to the physical
media is controlled.
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