Browse Prior Art Database

Getting rid of marking (RFC0064)

IP.com Disclosure Number: IPCOM000003711D
Original Publication Date: 1970-Jul-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 3 page(s) / 7K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Elie: AUTHOR

Abstract

Though we realize that this improvement is perhaps somewhat late to be implemented, we believe that there exist better solutions than marking and suggest a simple modification to the IMP-HOST interface which would avoid it.

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Network Working Group M. Elie

Request for Comments #64 UCLA

Getting Rid of Marking

Though we realize that this improvement is perhaps somewhat late

to be implemented, we believe that there exist better solutions than

marking and suggest a simple modification to the IMP-HOST interface

which would avoid it.

1. The harm.

Marking was introduced to suit the sending Host because it permits

the text of a message to start on a word boundary, however, it does not

suit the receiving Host with a different word length. Moreover,it

introduces in the message useless bits. Let us illustrate this by the

example of our Sigma 7, a 32 bit machine.

1.1 Inefficiency in Computation

Suppose we receive a message from an 18 bit machine (figure 1.1)

coded in 8 bit ASCII characters which will eventually become standard on

the network. In order to translate this message into our EBCDIC

internal code, for instance.

0 17 0 31

-------------------------- ------------------------------

| leader | | leader |

-------------------------- ------------------------------

| | 0 0 0 1| | 0 0 0 1 | |

-------------------------- ----------- |

| | | |

| | | |

| | | |

| message | | message |

| | | |

| | | |

| | | |

| | | |

| | | |

| | | |

figure 1.1

we first have to shift the whole message. We must detect the firsl 1

following the leader, and from this determine that we must shift the

message 4 bits to the left. This takes approximately 12 ┬Ásec per double

word, which makes 1,5 msec per full regular message. This is not huge,

but still it is about one-third of the time it will take to translate

the message in internal code.

1.2 Inefficiency in transmission

More important is the inefficiency resulting from adding

unnecessary bits to the message, especially if it turns out that one

...