TCP Flashcards
TCP page termination handshake
FIN, ACK
ACK
FIN, ACK
ACK
Three-way handshake
SYN
SYN, ACK
ACK
DCHP Port
Client uses UDP port 67 to send
Server uses UDP port 68 to send
NTP? Port?
Network time protocol
UDP port 123
SNTP? Port?
Simple network time protocol
UDP port 123
TFTP? Port?
Trivial file transfer protocol
UDP port 69
ICMP?
Internet control message protocol
IGMP? Use?
Internet group management protocol
Allows routers to communicate over multicast with group members
Assigned to a 244.0.0.0/4 address
Total range of all port numbers?
0-65535
Well-known port number range?
0-1023
Range of ephemeral port numbers? Use?
1024-5000
Generated randomly by web clients
Range of dynamic/private port numbers?
49152-65535
Range of registered port numbers?
1024-49151
Socket? Socket pair?
Socket: TCP session data (IP address and port) stored on a single computer
Socket pair: same info about both computers involved in the connection
Windows command to see active TCP sessions/connections
netstat -n
Open port?
A socket that is prepared to respond to any IP packets destined for its port number
Windows command to see all open ports
netstat -an
Netstat switches to show process ID for all TCP connections
- ano
- a shows all connections
- n shows raw numbers
- o shows process IDa
Netstat switch to show name of process using TCP connection
-b
HTTP port
TCP 80
NNTP port
TCP 119
HTTPS port
TCP 443
Telnet port
TCP 23
What is rLogin? Port?
Old UNIX program. Similar to telnet but could configure to log you in automatically.
TCP 513
What is RSH? Port?
Remote shell. Old UNIX program. Allows you to send single commands to remote server, can be integrated into scripts
TCP 514
What is RCP? Port?
Remote copy protocol. Old UNIX program. Allowed you to copy files to/from remote server without using FTP or NFS.
TCP 514
SSH port
TCP 22
SMTP port
TCP 25
POP3 port
TCP 110
IMAP4 port
TCP 143
FTP port
TCP 20, 21 (passive FTP only uses 21)
Passive vs. Active FTP
Passive: used behind NAT routers. Client sends FTP request on port 21. Server responds with random port, tells client which port it is listening on. Client sends data back to that port. Client initiates all conversations so NAT router knows where to send packets
