Transmission Control
Protocol
TCP
Transport layer function
3-Way Handshake
TCP hosts establish a connection-oriented
session with one another using a
______________________.
A virtual connection
_________________________________
_________________________________
________________________________
The process occurs by…
3-Way Handshake cont…
Host 1 sends a ____ packet to Host 2 (1st data
packet)
Host 2 _____ the packet from Host 1 (2nd data
packet)
______________________________________ for
Host 1 (2nd data packet)
Host 1 __________ packet from Host 2 (3rd
data packet)
Communication can now begin
DoS using SYN flooding
Denial of service (DoS) attacks are
designed to ______________________
_______________________________
SYN flooding exploits the normal three-
way handshake
causes targeted devices (generally a server)
to __________________________________
____________________________________
• Never completing the handshake and keeping the
server in a state of wait
• During this time, memory is allocated until the
connection times out
The server get flooded with these types of
requests
Solutions to this type of DoS
system administrators may _______
_____________________________
_____________________________
Purchase additional software used to
detect and defend against these
types of attacks
Review of these fields to follow…
TCP Segment Fields
Following are the definitions of some of the fields
in the TCP segment:
Source port -- __________________________
Destination port -- _______________________
Sequence number -- number used to ________
_____________________________________
Acknowledgment number - ______________
__________________________
Window -- number of octets that the sender is
______________________________________
_____________________________________
More to come…..
TCP simple acknowledgment
and windowing
Window size determines the ______
__________________________________
__________________________________
___________ (ACK) from the destination
TCP “Sliding Windows” _______________
__________________ by negotiating the
window size to account for more or less
segments to be transmitted as conditions
warrant
TCP _______________________________
__________________________________
TCP Sequencing
Each segment is numbered before
transmission.
_______________________________
______________________________
If a sequence number is missing in the
series, retransmission is needed
NOTE: the ACK (and SYN) field aka code
field
Review- UDP Segment Fields
•UDP very simple segment
•Header contains 4 fields
•Least amount of info as possible
UDP header determines the Calculated sum of
application to which a UDP header and data
segment will be delivered. fields
TCP & UDP Port Number Review
Both TCP and UDP use port (or socket) numbers to
pass information to the upper layers.
_________________________________________
_________________________________________
_________________________________________
Without a way to distinguish between different
conversations, the client would be unable to send both an
email and browse a web page, using one server at the
same time.
Port numbers in the range of _________________
___________________________________ (IANA)
Well known and agreed upon port numbers…
Review of Common Port Numbers
Numbers below 255 -
are for public
applications- most
common are… •FTP, Telnet,
SMTP, and HTTP-
port #80 (for
TCP)
• TFTP for UDP
Need for ports…
A host might have a telnet connection
(port 23) open, while at the same time be
surfing the net, port 80.
The IP and the MAC addresses would be the
same because the packets are coming from the
same host.
Each conversation on the source side
needs its own port number, and each
service requested needs its own port
number (ports 23 and 80).
SOCKET = _________________________
__________________________________
Mod 10 LAB
Finish previous MOD labs
Lab 10-1: Multiple Active Host Sessions
Lab 10-2: Well –Known port numbers and
multiple sessions
Start reviewing for hands-on-practical
Know how to program an “out-of-the-box”
router using line commands only- NOT setup
mode