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SEVENSTAX TCP/IP is an Internet protocol stack developed specifically for application in embedded systems. The SEVENSTAX TCP/IP-PPP variant allows transfer of IP packets via a serial interfaces. Theses interfaces are e.g. modems (analog, ISDN or GSM/GPRS/UMTS/LTE), UART/RS232 or serial connections via Bluetooth (SPP, DUN).

In addition to the Internet Protocol Version 4 (IPv4) all important protocols are included.

  • Internet Protocol Version 4 (IPv4) based on RFC 791 
    • Subnet mask with CIDR blocks (Classless Inter-Domain Routing, RFC 1518 and RFC 1519) 
    • IP fragmentation and reassembly according to RFC 791, RFC 815 
    • Validation of IP address/subnet (RFC 3330) 
  • Transmission Control Protocol (TCP) based on RFC 675, RFC793, RFC 1323
    • Checksum according to RFC 1071
    • TCP extensions according to RFC 1323
    • Error correction algorithms (RFC 1122) 
    • Simultaneous operation in TCP server and TCP client mode 
    • No limitation of simultaneous connections 
    • Full frame size control (TCP segmentation according to RFC 879)
    • Sliding window technique (RFC 793)
    • Keep-alive packets (RFC 1122) 
    • Protection against “Sequence Number Attacks” (RFC 1948)
    • Fast retransmission algorithm
  • User Datagram Protocol (UDP) based on RFC 768
  • Domain-Name-System (DNS) client based on RFC 1034, RFC 1035
  • Internet Control Message Protocol (ICMP) based on RFC 792
    • Sending ICMP host messages
    • Receiving ICMP host and router messages
  • Internet Group Management Protocol (IGMP)
    • Version 1 (RFC 1112)
    • Version 2 (RFC 2236)
  • (Simple) Network Time Protocol (NTP/SNTP) based on RFC 958, 4330

Point-to-Point Protocol (PPP)

PPP (Point-to-Point-Protocol)-Client and-Server based on RFC 1661 for Transmission of IP-packets uing serial interfaces:

  • 'On the fly' HDLC encoding/decoding (RFC 1662)
  • Configuration and connection establishment with 
    LCP (Link Control Protocol)
  • Authentication using CHAP (RFC 1994) and PAP (RFC 1334)
  • Data compression with CCP (Compression Control Protocol)
  • IP-Configuration with IPCP (IP Control Protocol, RFC 1332)
  • IP-Header-Compression (Van Jacobson Compressed TCP/IP)
  • Protocol-Compression 
  • Supports ACCM (Asynchronous Control Character Map) 
  • automatic connection check (AutoPing)
  • PPP Identification-Message

Modem Connection Service

SEVENSTAX TCP/IP-PPP includes the SEVENSTAX Modem Connection Service (MCS). MCS is a module to monitor and control modems. A universal AT driver allows easy and fast connection of various modems (analogues, ISDN or GSM/GPRS/UMTS/LTE). SEVENSTAX MCS supports changing of the modems during runtime. Thereby, modems can be designed as changeable modules. Depending on the purpose a suitable modem can be inserted.

Features of SEVENSTAX MCS:

  • Extended AT command set 
  • Extensive modem state machine 
  • Error management upon broken connections 
  • Monitoring of telephone numbers on call acceptance (PPP-dial-in) 
  • Support of different modems with one firmware 
  • Automatic identification of modems

For GSM/GPRS/UMTS/LTE modems the following additional functions are supported:

  • Request and set a PIN
  • Limitation of PIN requests (not supported by all modems) 
  • Secret PIN: The PIN is generated by a secret function of the IMSI (International Mobile Subscriber Identity)
  • Scanning of signal strength
  • Sending and receiving of SMS 
  • State machine for CSD and GPRS/UMTS/etc. 
  • Permanent connection via GPRS/UMTS 

Adaptations of the universal AT driver are available for numerous modems. We also offer adaptations to so far unsupported modems.