network20250316.txt

(C) David Vajda
2025-03-16
Network Technology

ASCII
    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
    FF      Form Feed
    LF      Line Feed
    CR      Carriage Return
    CAN     Cancel
    DEL     Delete
    ACK     Acknowledge
    NAK     Not Acknoledge
    SI      Shift Out
    SO      Shift In
    DC1     Device Control 1

X-ON/X-OFF - DC1/DC3 oder SI/SO? Strg-S/Strg-Q
ACK/NAK

Handshaking
Dataflowcontroll - Datenfluss kontrolle

RS232
    1 Start Bit
    1 oder 2 Stop Bit
    Parity odd even non
    5 6 7 8 9 Data Bit

Baud Rate

Asynchron - kein gemeinsamer Takt

CCITT-1 Baudot-Code 1
Baud: Anzahl der Zeichen eines Zeichensatzes pro Sekunde

RS232
MAX232
    R1IN
    R2IN
    T1IN
    T2IN
    R1OUT
    R2OUT
    T1OUT
    T2OUT

Terminal: Datenendgeraet
Datenuebertragungsgeraet: Modem z.B.

TxD: Transmit Data
RxD: Recieve Data
RTS: Request To Send
CTS: Clear To Send
DSR: Data Set Ready
DTR: Data Terminal Ready

Sub-D-9 Stecker

UBRR UBRRH UBRRL UART Baud Rate Register
UCSRA UCSRB UCSRC UART Controll and Status Register
UDR UART Data Register

Ports - Application Layer
    15 netstat
    20 ftp
    22 ssh
    25 smtp
    53 nfs
    80 http
    110 pop3
    143 imap
    587 smtps

DNS - Records
    A IPv4 Address Record
    AAAA
    TXT
    MX Mail eXchange Record
    PTR Pointer Record

TCP
    Source Port (2 Byte)
    Destination Port (2 Byte)
    Sequence Number (4 Byte)
    Acknoledge Number (4 Byte)

    Reserved

IP
    TTL IHL DSCP
    Source IP Address
    Destination IP Address

iptables
    tables
    chains

    tables
        nat mangle raw
    chains
        PREROUTING
        INPUT
        FORWARDING
        OUTPUT
        POSTROUTINGs

    -j ACTION
        ACCEPT
        DROP
        REJECT
        LOG
    -d IP ADDR
    -s IP ADDR
    -dport --destination-port
    -sport --source-port
    -p tcp/icmp/udp

    -A INPUT

if iptables
netstat route traceroute
whois
nslookup
reverse dns lookup
ping