Transfer Syntax Notation One (TSN.1)

A formal notation for describing messages in binary protocols

Features & Benefits

  • Support flexible and custom message encoding.
  • Handle messages that cannot be described by ASN.1.
  • Handle all CSN.1 messages yet is more intuitive and more compiler friendly.
  • Suitable for both standards based and proprietary messages.
  • Enable software development tools to auto-generate message parsers.
  • Independent of machine architecture and implementation language.
  • Validated against many wireless standards including GSM/UMTS/LTE, CDMA2000, and WiMAX.

Introduction

Messages in binary protocols are often defined using ad hoc encodings. They are especially prevalent in bandwidth constrained systems such as wireless protocols where bit efficiency is important. These messages cannot be easily described using existing message description languages such as ASN.1, or in the case of CSN.1, the notation does not support message parser generation well.

Without a formal notation to capture this type of messages, they are often described informally using tables, illustrations, and plain English. This forces software engineers to implement the message parsing code by hand. Some standards define a large number of messages, many of which have complicated structures. Hand coding these parsers leads to long development cycles and error-prone code.

All that has changed with the introduction of the Transfer Syntax Notation One (TSN.1). The notation is designed specifically for messages that require flexible and custom encoding. TSN.1 enables system designers to define a message directly in terms of the actual bit sequence transmitted. In various literatures, this is often referred as the concrete or transfer syntax of a message. As demonstrated by our flagship product, TSN.1 Compiler (patent pending), software development tools can be used to automatically generate message parsers.

TSN.1 Examples

As illustrated in the following examples, message in many existing network communication standards can be naturally expressed in TSN.1. For a complete specification of TSN.1, please refer to the TSN.1 Specification document.

TCP/IP Header Formats

TCPHeader() ::=
{
   SourcePort             16;
   DestinationPort        16;
   SequenceNumber         32;
   AcknowledgementNumber  32;
   HLen                   4;
   reserve                6;

   // Code Bits
   URG                    1;
   ACK                    1;
   PSH                    1;
   RST                    1;
   SYN                    1;
   FIN                    1;

   Window                 16;
   CheckSum               16;
   UrgentPointer          16;

   Options                (HLen - 5) * 32;
}

IPHeader() ::=
{
   Version               4;
   HLen                  4;
   ServiceType           8;
   TotalLength           16;
   Identifcation         16;
   Flags                 3;
   FragmentOffset        13;
   TimeToLive            8;
   Protocol              8;
   HeaderCheckSum        16;
   SourceIPAddress       32;
   DestinationIPAddress  32;
   Options               (HLen - 5) * 32;
}

CDMA2000 1X

is2000_fdsch_HDM() ::=
{
   USE_TIME      1;
   ACTION_TIME   6;
   HDM_SEQ       2;
   SRCH_WIN_A    4;
   T_ADD         6;
   T_DROP        6;
   T_COMP        4;
   T_TDROP       4;
   FRAME_OFFSET  4;
   PRIVATE_LCM   1;
   RESET_L2      1;
   ENCRYPT_MODE  2;
   FREQ_INCL     1;

   if(FREQ_INCL == 1)
   {
      CDMA_FREQ  11;
   }

   PILOTS[]  :
   {
      PILOT_PN      9;
      PWR_COMB_IND  1;
      CODE_CHAN     8;
   }
}

CDMA2000 1xEV-DO

is856_rup_TrafficChannelAssignment() ::=
{
   var N  4;

   MessageSequence  8;
   ChannelIncluded  1;

   if(ChannelIncluded == 1)
   {
      Channel  :
      {
         SystemType     8;
         BandClass      5;
         ChannelNumber  11;
      }
   }

   FrameOffset     4;
   DRCLength       2;
   DRCChannelGain  6;
   AckChannelGain  6;
   NumPilots       4;

   Pilots[NumPilots]  :
   {
      PilotPN        9;
      SofterHandoff  1;
      MACIndex       6;
      DRCCover       3;
      RABLength      2;
      RABOffset      3;

      if(SofterHandoff == 0)
      {
         N = N + 1;
      }
   }

   optional RELEASE_A :
   {
      MACIndexMSBsIncluded  1;

      if(MACIndexMSBsIncluded == 1)
      {
         MACIndexMSBs[NumPilots] :
         {
            MACIndexMSB    1;
            RAChannelGain  2;
         }

         DSCChannelGain  5;

         DSC[N]  3;
      }
   }
}

GSM/UMTS/LTE

ts24008_AttachRequest() ::=
{
   SkipIndicator          4 = 0x0; // 0000
   ProtocolDiscriminator  4 = 0x8; // 1000
   MessageType            8 = 0x1; // 00000001

   MSNetworkCapability     : ts24008_MSNetworkCapabilityIE;
   CipheringKeySequence    : ts24008_CipheringKeySequenceIE;
   AttachType              : ts24008_AttachTypeIE;
   DRXParameter            : ts24008_DRXParameterIE;
   PTMSIorIMSI             : ts24008_MobileIdentityIE;
   OldRoutingAreaId        : ts24008_RoutingAreaIdIE;
   MSRadioAccessCapability : ts24008_MSRadioAccessCapabilityIE;

   OptionalIES[] : // variable number of optional IEs
   {
      IEI_MSN  4; // IEI most significant nible

      if(IEI_MSN == 9) // TMSI Status
      {
         reserve   3;
         TMSIFlag  1;
      }
      else
      {
         IEI_LSN  4; // IEI least significant nible

         IE  : case (IEI_MSN << 4 | IEI_LSN)  of
         {
            0x19 => OldPTMSISignature   : ts24008_PTMSISignatureIE;
            0x17 => RequestedReadyTimer : ts24008_GPRSTimerIE;
            0x33 => PSLCSCapability     : ts24008_PSLCSCapabilityIE;
               _ => UnknownIE           : ts24008_UnknownIE;
         }
      }
   }
}

IEEE 802.11/WiFi

wifi_mac_CapabilityInformation() ::=
{
    ESS             1;
    IBSS            1;
    CFPollable      1;
    CFPollRequest   1;
    Privacy         1;
    ShortPreamble   1;
    PBCC            1;
    ChannelAgility  1;
    reserve         2;
    ShortSlotTime   1;
    reserve         2;
    DSSS_OFDM       1;
    reserve         2;
}

IEEE 802.16/WiMAX

wimax_mac_ARQFeedbackIE() ::=
{
   CID         16;
   LAST        1;
   ACKType     2;
   BSN         11;
   NumACKMaps  2;

   if(ACKType != 1)
   {
      ACKMaps [ NumACKMaps + 1 ]  : // Array of ACKMaps
      {
         if(ACKType != 3)
         {
            SelectiveACKMap  16;
         }
         else
         {
            SequenceFormat  1;

            if(SequenceFormat == 0)
            {
               SequenceACKMap   2;
               Sequence1Length  6;
               Sequence2Length  6;
               reserve          1;
            }
            else
            {
               SequenceACKMap   3;
               Sequence1Length  4;
               Sequence2Length  4;
               Sequenc32Length  4;
            }
         }
      }
   }

   if(LAST != 1)
   {
      Next  : wimax_mac_ARQFeedbackIE; // Recursion
   }
}