source

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Destination
Reassembly Required
router
IP packet fragments
Fragments Created
router
IP packet
source
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TCP

• Connection Oriented
• state
• Stream Oriented
• Sequence number
• Full Duplex
• Reliable
• acknowledgment

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TCP Commands

• Syn synchronize sequence numbers
• Ack acknowledgement
• Fin close connection
• Push send data immediately
• Urgent look at data out of sequence
• Reset reject connection

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TCP Connection

• Passive Open
• Server opens known port and waits for client to
  connect (no traffic on network)
• Active open
• Client opens any available port and connects to
  server on known port (starts three way handshake)

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TCP Connection States
LISTEN Server waiting
SYN-SENT Waiting for ack
SYN-RCVD Syn received
ESTABLISHED Connection established
FIN-WAIT-1 Closing requested
FIN-WAIT-2 Closing accepted
CLOSE-WAIT Server waiting for client to close
LAST-ACK Server waiting for last ack
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Active open/syn
Passive open
Syn/ synack
Synack/ack
ack
Fin/ack
Close/fin
Ack/
Close/fin
Fin/ack
timeout
ack
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TCP Sliding Window

• Sequence No. - number of first byte in the
  segment
• Acknowledgement number of next byte expected
• Sliding Window number of bytes that can be
  transmitted without an acknowledgement

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Sender
K S U G O L D E N F L A S H E S
Sliding Window
Receiver

Sliding Window
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Sent, not yet acked
K S U G O L D E N F L A S H E S
Ready to send
Sliding Window
K S U
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Sent, not yet acked
K S U G O L D E N F L A S H E S
Sent and ACKed
Sliding Window
Ready to send
K S U D E N F L A
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K S U G O L D E N F L A S H E S
Sent and ACKed
Sliding Window
K S U G O L D E N F L A
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Server
Client
Syn
Seq 7280
Client sends syn to open connection
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Server
Client
Syn
Seq 5965 Ack 7281
Syn, Ack
Server sends Ack and Syn
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Server
Client
Syn
Syn, Ack
Ack
Cient sends Ack, connection is established
Seq 7281 Ack 5966
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Server
Client
Syn
Syn, Ack
Ack
Ack, Push
Client requests Web Page
Seq 7281 Ack 5966
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Server
Client
Syn
Syn, Ack
Ack
Ack
Server sends first part of Web Page
Ack
Seq 5966 ack 7532
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Server
Client
Syn
Syn, Ack
Ack
Ack
Server sends remainder of page
Seq 5966 ack 7531 Seq 7426 ack 7531
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Server
Client
Syn
Syn, Ack
Ack
Ack
Ack
Client sends ack
Seq 7531 ack 8886
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Server
Client
Syn
Syn, Ack
Ack
Ack
Server starts closing of connection
Ack
Ack, Fin, Push
Seq 8886 ack 7531
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Server
Client
Syn
Syn, Ack
Ack
Ack
Ack
Ack, Fin, Push
Ack
Client acks closing of servers side of connection
Seq 7531 ack 9203
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Server
Client
Syn
Syn, Ack
Ack
Ack
Ack
Ack, Fin, Push
Seq 7531 ack 9203
Ack
Ack, Fin
Client requests closing of its side of connection
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Server
Client
Syn
Syn, Ack
Ack
Ack
Ack
Ack, Fin, Push
Seq 9203 ack 7532
Ack
Ack, Fin
Server sends Ack, connection closed
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http//www.rhyshaden.com/arp.htm
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0
8
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TYPE
CODE
CHECKSUM
IDENTIFIER
SEQUENCE NUMBER
OPTIONAL DATA
ICMP Echo message
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ftp client
ftp server

131.123.8.111
131.123.250.211
2349
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2353
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TCP Segments
Proto Local Address Foreign Address
TCP 131.123.8.1112349 131.123.250.21121
TCP 131.123.8.1112353 131.123.250.21120