tcpip20250329.txt

(C) David Vajda
2025-03-29
TCP/IP Networking auswendig

ASCII-Codes

NUL     Nullzeichen
SOH     Start of Heading
STX     Start of Text
ETX     End of Text
EOT     End of Transmission
ETB     End of Transmission Block
LF      Line Feed
FF      Form Feed
HT      Horizontal Tab
VT      Vertical Tab
BS      Backspace
CAN     Cancel
DEL     Delete
SI      Shift In
SO      Shift Out
DC1     Device Control 1
...
DC4     Device Control 4
ACK     Acknowlege
NAK     Not Acknowlege

Handshaking
X-ON/X-OFF
ACK/NAK

1.) Hardware
2.) Software
3.) Protokoll

Dataflow = Datenfluss

GND     Ground
TxD     Transmit Data
RxD     Read Data
CTS     Clear To Send
RTS     Ready To Send
DSR     Data Set Ready
DTR     Data Terminal Ready

Terminal - datenendgeraet
Datenuebertragungsgeraet - z.B. Modem

RS-232, CCITT-5

1 oder 2 stopbit
1 startbit
5, 6, 7, 8, 9 Datenbit
keine gerade oder ungerade paritaet

odd, even

Baudrate: z.B.
    1200
    2400
    4800
    9600

UBRR - USART Baud Rate Register
UBRRH - UBRRL
UCSRC UCSRC UCSRA USART Controll and Status Register
UDR - USART Data Register

RXEN - Recieve enable
TXEN - Transmit enable

URSEL
UCSZ1 UCSZ0

Clear: Erlaubnis
Ready: Bereit
Prepare: Bereit halten
Acknowlege: Bestaetigiung

25: entspricht in UBRRH, und UBRRL, Atmega8 - 2400

Application Layer - Ports
    15  Netstat
    20  FTP
    22  SSH
    25  SMTP
    53  DNS
    80  HTTP
    110 POP3
    143 IMAP
    586 SMTPS


DNS - Records
    A - IPv4
    AAAA - IPv6
    TXT - Text Record
    MX - mail eXchange
    CNAME - Cannonical Name - kanonisch - Richtschnur
    PTR - Pointer Record

TCP/IP
    Source Port (2 Byte)
    Destination Port (2 Byte)
    Sequence Number (4 Byte)
    Acknowlege Number (4 Byte)
    Data Offset (5 Bit)
    Reserved
    Flags
        ...
    ...

IP
    Source Address
    Destination Address
    TTL - Time 2 Live
    DSCP
    IHL
    ...

Networking Binarys
    ip ifconfig
    telnet
    route
    traceroute
    tracepath
    ping
    wget
    iptables
    netstat

iptables
    tables
    chains

    tables
        filter
        nat
        mangle
        raw

    chains
        INPUT
        PREROUTING
        FORWARD
        POSTROUTING
        OUTPUT
    action
        DROP
        REJECT
        ACCEPT
        LOG
        ...

    -d Destination Address
    -s Source Address

    -sport --source-port
    -dport --destination-port

    -p protocoll
        tcp/icmp/udp
    -j Action

    -A CHAIN

....

encryption algorithmns
    IDEA 3DES CAST5
    AES AES-192 AES-256
    CAMELLIA-192 CAMELLIA-256 CAMELLIA-512
    BLOWFISH
    TWOFISH