indra@amdcad.AMD.COM (Indra K. Singhal) (06/03/88)
Has anyone put together a program/shell script that converts
/etc/hosts to the standard RR format as specified in the RFCs listed?
Thought I'd ask before I get a coleague to spend time reinventing
it. Thanks !!
--
Indra K. Singhal | |
{ucbvax,decwrl,allegra}!amdcad!indra | This space for rent ! |
amdcad!indra@decwrl.dec.com | |
(408) 749-5445(w) | | KASTEN@MITVMA.MIT.EDU (Frank Kastenholz) (06/09/88)
In article <8805261929.AA04199@RHEA.CAM.UNISYS.COM>, jonab@CAM.UNISYS.COM (Jonathan P. Biggar) writes: >>> The TCP URGENT mechanism uses a pointer; I do not think that there >>> is any specification which says that packet boundaries are >>> significant with respect to URGENTs. >> Not so! RFC 793 states: >> If there is urgent data [...]. *****Note that data following >> the urgent pointer (non-urgent data) cannot be delivered to the >> user in the same buffer with preceeding urgent data unless the >> boundary is clearly marked for the user.***** > >What does this have to do with packet boundaries? Jonab said "packet", >not "user buffer". This sounds to me like there is some confusion over the meaning of some of the terms used (which, to the best of my limited knowledge, have never been fully codified - perhaps an addendum to the Assigned Numbers RFC is in order - "Assigned Abbreviations and Terms and Their Meanings"). As I understand things the "hierarchy" of terms in use in the Internet protocols (among others) are: FRAME - lowest level of bits/bytes. One speaks of Ethernet Frames, etc A FRAME has ONE data link header (e.g. Ethernet header). FRAGMENT - the thing that IP spits out to the data link driver. Each FRAGMENT has ONE IP header. A FRAGMENT may be split into multiple FRAMES by the lower layers. SEGMENT - the thing that TCP spits into IP. Each SEGMENT has one TCP header. It may be broken into FRAGMENTS by IP. Noe things get a little weird..... DATAGRAM - this is also the 'larger' thing that IP tries to send. A DATAGRAM USUALLY has a one to one relationship with a SEGMENT. It may be broken up (fragmented) into a number of FRAGMENTS by IP before being sent through the data link. A DATAGRAM is ALSO what UDP and other "datagram" oriented protocols may give to IP for transmission. PACKET - a generic term that can mean anything at any time - usually its meaning is derived from the context, other times by a prefix (such as IP PACKET), other times ..... BUFFER - what is passed to TCP/UDP for transmission. Usually. Of course, a device driver reads stuff out of the I/O interface into a buffer.... These are terms that I use, based on "common usage, the literature, etc" Frank Kastenholz.
cire@CLASH.CISCO.COM (06/10/88)
>> Date: Thu, 09 Jun 88 09:33:04 EDT >> From: Frank Kastenholz <KASTEN@MITVMA.MIT.EDU> >> Subject: Re: Convert /etc/hosts to RR format pgm anyone? >> To: der Mouse <mcgill-vision!mouse@bloom-beacon.mit.edu> >> Cc: tcp-ip@sri-nic.arpa >> Good start! I've added some corrections to the heirarchy. It strikes me that this kind of info would be reasonable in an intro of some kind to IP. >> This sounds to me like there is some confusion over the meaning of >> some of the terms used (which, to the best of my limited knowledge, >> have never been fully codified - perhaps an addendum to the Assigned >> Numbers RFC is in order - "Assigned Abbreviations and Terms and Their >> Meanings"). >> I'd recommend Douglas Comer's book 'Internetworking with TCP/IP, Principals, Protocols, and Architecture' or Andrew Tanenbaum's book 'Computer Networks'. Both include a glossary at the back with very succinct definitions of most everything you mention below. >> As I understand things the "hierarchy" of terms in use in the Internet >> protocols (among others) are: >> Here is perhaps a better set of definitions: (some of these are essentially pulled from Comer's book). FRAME - The unit of information encapsulated for transmission on physical media or network. FRAGMENT - a unit that the IP layer breaks a DATAGRAM into if necessary for transmission across networks that can not handle the size of the entire DATAGRAM. A FRAGMENT has essentially the same IP header as the original DATAGRAM. DATAGRAM - The basic unit of information dealt with by the IP layer. This is what is sent across the TCP/IP Internet. It may be broken into FRAGMENTS if a network can not handle the DATAGRAM's size. SEGMENT - the basic unit that TCP deals with. A segment consists of a block of bytes that arrive or are sent at one time. These bytes make up part of stream of bytes. Information in the segment identifies where in the stream these bytes exist. A segment will be passed to the IP layer as one or more DATAGRAMS for transmission by that layer. PACKET - the basic unit of information sent across a packet-switching network. It's exact meaning is dependent upon the context. BUFFER - an implementation detail that is used for passing blocks of information including DATAGRAMS to the layers for processing. -c cire|eric Eric B. Decker cisco Systems Menlo Park, California email: cire@cisco.com uSnail: 1360 Willow Rd., Menlo Park, CA 94025 Phone : (415) 326-1941