tcpip20250404.txt

(C) David Vajda
2025-04-04
TCP/IP Networking

ASCII Code
NUL     Null
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      Feed Feed
SO      Shift Out
SI      Shift In
DC1     Device Controll 1
CAN     Cancel
DEL     Delete
ESC     Escape
ACK     Acknowlege
NAK     Not Acknowlege
...

RS-232, CCITT-5

RxD     Recieve Data
TxD     Transmit Data
GND     Ground
CTS     Clear 2 Send
RTS     Ready 2 Send
DSR     Data Set Ready
DTR     Data Terminal Ready

...

Handshaking - Data Flow Controll
    Hardware
    Software
    Protocoll

5, 6, 7, 8, 9 Data Bits
no odd even parity
1/2 Stop Bit
1 Start Bit
Baudrate
    1200
    2400
    4800
    9600

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

TXEN - Transmit Enable
RXEN - Recieve Enable
URSEL
UCSZ1 UCZS0

Terminal - Datenendgeraet
Modem - Datenuebertragungsgeraet


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

DNS - Records
    A       IPv4
    AAAA    IPv6
    PTR     Pointer Record
    MX      mail eXchange
    CNAME   Cannonical Name (Kanonisch ^= Richtschnur)
    TXT     Text Record

TCP
    Source Port (2 Byte)
    Destination Port (2 Byte)
    Sequence Number (4 Byte)
    Acknowlegement Number (4 Byte)
    Data Offset (5 Bit)
    Reserved
    Flags
        ...
    Recieved Window
    Checksum
    Urgent Pointer
    Options

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

tcp/ip binaries
    ifconfig ip
    netstat
    telnet
    ping
    curl
    wget
    traceroute tracepath route
    whois

iptables
    tables
    chains

    tables
        filter
        nat
        mangle
        raw
    chains
        INPUT
        PREROUTING
        FORWARD
        POSTROUTING
        OUTPUT
    -A CHAIN
        INPUT
        PREROUTING
        ...
    -j ACTION
        DROP
        ACCEPT
        REJECT
        LOG
        ...
    -dport --destination-port
    -sport --source-port

    -d DESTINATION ADDRESS
    -s SOURCE ADDRESS

    -p PROTOCOLL
        icmp/udp/tcp

IDEA 3DEST CAST5 BLOWFISH
AES AES-192 AES-256
TWOFISH
CAMELLIA-192 CAMELLIA-256 CAMELLIA-512