The following errata report has been submitted for RFC5595, "The Datagram Congestion Control Protocol (DCCP) Service Codes". -------------------------------------- You may review the report below and at: http://www.rfc-editor.org/errata_search.php?rfc=5595&eid=1891 -------------------------------------- Type: Technical Reported by: Alfred Hoenes <ah@xxxxxxxxx> Section: 2.7, pg.10 Original Text ------------- int s_port; /* server port */ s_port = ((sc[0]<<7)^(sc[1]<<5)^(sc[2]<<3)^sc[3]) | 0xC000; [...] where [...] This algorithm has the following properties: o [...] o [...] | o It preserves the 4 lowest bits of the final bytes of the Service Code, which allows many common series of Service Codes to be | mapped to a set of adjacent port numbers, e.g., Foo1, and Foo2; | Fooa and Foob would be assigned adjacent ports. (Note: this | consecutive numbering only applies to characters in the range 0-9 | and A-O and P-Z. When the characters cross a range boundary, the | algorithm introduces a discontinuity, resulting in mapping to | non-consecutive ports. Hence, Fooo and Foop respectively map to | the decimal values of 65015 and 65000). Corrected Text -------------- | o It preserves the 3 lowest bits of the final bytes [...] | ... [[ t.b.d. ]] Notes ----- Simply trying the full example shows that the statement is not entirely correct. The quoted formula reveals that only the least significant *3* bits are left unchanged (due to the '<<3' operation on sc[2]). It turns out that ranges of *8* contiguous SC values are mapped to contiguous 8 port numbers but, depending on the two least significant bits of sc[2], groups of 4 adjacent ranges are shuffled around. More complicated patterns arise for the next higher level of 4-clusters of range-groups, etc. Thus, the situation is not hopeless for the indicated purpose, but much more complicated than indicated in the RFC text. I leave it as an exercise to the interested reader to figure out the details for the size of range she is interested in. A future revision of the RFC however should fix the text. [[ Verifiers: please edit this text and insert a full-fledged replacement text, should it be provided by a third party and be acceptable to the authors and the WG. ]] Instructions: ------------- This errata is currently posted as "Reported". If necessary, please use "Reply All" to discuss whether it should be verified or rejected. When a decision is reached, the verifying party (IESG) can log in to change the status and edit the report, if necessary. -------------------------------------- RFC5595 (draft-ietf-dccp-serv-codes-11) -------------------------------------- Title : The Datagram Congestion Control Protocol (DCCP) Service Codes Publication Date : September 2009 Author(s) : G. Fairhurst Category : PROPOSED STANDARD Source : Datagram Congestion Control Protocol Area : Transport Stream : IETF Verifying Party : IESG
