2.1.3.1 Clarifications for RFC 3208

  • Article

The following values SHOULD<4> be used for the constants defined in [RFC3208].

Constant

Value

TXW_MAX_RTE

70 kilobytes per second

TXW_SECS

300

TXW_ADV_SECS

15% of TXW_SECS

TXW_ADV_IVL

15% of TXW_SECS

IHB_MIN

1 second

IHB_MAX

15 seconds

NAK_RPT_IVL

0.75 seconds

NAK_RDATA_IVL

2 seconds

NAK_NCF_RETRIES

10

NAK_DATA_RETRIES

10

Token bucket size

40 milliseconds

In addition, [RFC3208] allows flexibility in implementing the following details:

  • The NAK_RB_IVL timer SHOULD be chosen randomly from the interval [0.05, 0.01] seconds.

  • The source path message (SPM) ambient time interval MUST be implemented such that ambient SPMs are sent when either 50 data packets (ODATA or RDATA packets) have been transmitted, or 0.5 seconds have passed since the last ambient SPM, whichever comes sooner.

  • Section 5.3 of [RFC3208] allows a source to delay RDATA retransmission to accommodate the arrival of additional negative acknowledgments (NAKs). An implementation of this specification SHOULD delay the retransmissions by a time computed according to the following formula.

     RDataDelayTime = 
 ((RDataSequenceNumber - TrailingSequenceNumber) * 60 msecs) / 
 ((LastODataSentSequenceNumber - TrailingSequenceNumber + 1))

  • Section 16 of [RFC3208] allows implementations to implement any scheme for advancing the transmit window. Implementations of this specification SHOULD advance the transmit window every TXW_ADV_IVL.

  • Implementations of this specification SHOULD delay transmit window advancement if the sender has pending NAK requests in the range of sequences that the trailing edge of the window is supposed to advance over. In this case, the trailing edge only advances up to the first pending NAK request.

  • Implementations of this specification SHOULD limit the size of application data packets (APDUs) to 64 kilobytes to protect the server from denial of service attacks.