Selective Acknowledgement; Large Windows - Novell NETWARE 6-DOCUMENTATION Manual

Selective Acknowledgement

Large Windows

40
NetWare TCP/IP Administration Guide
Multihoming (page 41)
Multiple Default Gateway (page 43)
Dead Gateway Detection (page 43)
Path MTU Black Hole Detection and Recovery (page 44)
Provision of Non-ARPable Secondary IP Address (page 45)
The Selective Acknowledgment (SACK) is a mechanism that includes a
retransmission algorithm which helps overcome weak links on the TCP/IP
stack.
The selective acknowledgment extension uses two TCP options. The first is
an enabling option, SACK-permitted, which can be sent in a SYN segment to
indicate that the SACK option can be used once the connection is established.
The SACK-permitted option is a two-byte option.
The second option is the SACK option itself, which can be sent over an
established connection once both the sender and the receiver have
successfully negotiated the SACK-permit option. Whenever there is loss of
data, the data receiver can send the SACK option to acknowledge the out-of-
order segments.
For more information on this, see
The Large Windows option allows windows larger than 2**16. It defines an
implicit scale factor, which is used to multiply the window size value found in
a TCP header to obtain the true window size which can go up to a maximum
limit of 1 GB.
This Large Window option is negotiated while establishing the connection.
For more information on this, see
"Selective Acknowledgement" on page
"Large Windows" on page
57.
55.