tcp20250318.txt

(C) David Vajda
Tue Mar 18 09:08:49 2025
TCP/IP auswendig, uebung

ASCII

NUL     Nullzeichen
SOH     Start of Heading
STX     Start of Text
ETX     End of Text
EOT     End of Transmission
ETB     End of Transmission Block
HT      Horizontal Tab
VT      Vertical Tab
LF      Line Feed
FF      Form Feed
CR      Carriage Return
BS      Backspace
DEL     Delete
CAN     Cancel
ACK     Acknowlege
NAK     No Acknowlegement
SYN
SO      Shift OUT
SI      Shift IN
DC1...  Device Controll

ACK/NAK Protokoll
X-ON/X-OFF Protokoll Strg-Q/Strg-S

handshaking

RxD     Recieve
TxD     Transmit
RTS     Ready to Send
CTS     Clear to Send
DSR     Data Set Ready
DTR     Data Terminal Ready

Terminal - Datenendgeraet
Datenuebertragungsgeraet

UBBR UBRRH UBRRL - USART Baud Rate Register
UCSRC UCSRB UCSRA - USART Controll and Status Register
UDR - USART DATA Register

1 oder 2 Stopbit
1 Startbit
no odd even parity
5 6 7 8 9 Data Bits

Baud-Rate

Application Layer Port
    15 NETSTAT
    20 FTP
    22 SSH
    25 SMTP
    53 DNS
    80 HTTP
    110 POP3
    143 IMAP
    443 HTTP
    587 SMTPS

Records DNS
    A IPv4
    AAAA IPv6
    TXT
    MX Mail eXchange Record
    PTR Pointer Record
    CNAME Cannonical Name Record

TCP
    Source Port (2 Byte)
    Destination Port (2 Byte)
    Sequence Number (4 Byte)
    Acknowegement Number (4 Byte)
    Data Offset ???
    Reserverd
    Flags

IP
    TTL DSCP IHL
    Source IP
    Destination IP

iptables
    chains
    tables

    tables
        filter nat mangle raw

    chains
        INPUT
        PREROUTING
        FORWARD
        POSTROUTING
        OUTPUT
    action
        DROP
        ACCEPT
        REJECT
        LOG
        ...
    Protocoll
        tcp
        icmp
        udp

    -d Destination Address
    -s Source Address
    --dport Destination Port
    --sport Source Port
    -j Action
    -A CHAIN
    -p Protocoll