- A window is a
consecutive range of sequence number
- Sender window:
- Sender window =
sequence numbers that the
sender
can use to
label
an outstanding frame
- The sender must buffer (= retain) an outstanding frame in its send buffer
- Sender Window Size (SWS) = # buffers in the sender buffer
- Sender window =
sequence numbers that the
sender
can use to
label
an outstanding frame
- Receiver window:
- Receiver window
=
sequence numbers of
data frames
that the receiver will
buffer (when they are received)
- If the first frame
in the receiver window
is received:
- The receiver will also deliver some frames (from its receive buffer).
- And slide the receive window forward by the number of frames delivered
- Receiver Window Size (RWS) = # buffers in the receiver buffer
- Receiver window
=
sequence numbers of
data frames
that the receiver will
buffer (when they are received)
- Fact:
- Sender Window Size
and Receiver Window Size
can be different
But:
Sender Window Size ≤ Receiver Window Size
because: send buffer size ≤ receive buffer size
See: click here
- Sender Window Size
and Receiver Window Size
can be different
- Sliding window
movement
(= update algorithm):
- Initially, the
sender and
receiver window
must
have the
same starting
number (i.e., "lined up")
- Sender window will
slide (forward)
when:
- the first data frame
in the sender window is
acknowledged
(then the sender can release some buffers !)
- the first data frame
in the sender window is
acknowledged
- Receiver window will
slide (forward)
when:
- the first data frame
in the receiver window is
received
(then the receiver can deliver some data frames !)
- the first data frame
in the receiver window is
received
- Initially, the
sender and
receiver window
must
have the
same starting
number (i.e., "lined up")