On Mon, Feb 10, 2014 at 11:21 AM, Scott Griepentrog <[email protected] > wrote:
> If it helps understanding the difference between DSCP and TOS, here is a > table I put together years back that shows all the common values. > > QoS Values are very confusing, so I'm making a table of the different > types of values that mean the same thing. > To highlight the problem... a pjsip transport uses column 6 to set the signalling because pjproject only accepts DSCP decimal values but a pjsip endpoint uses column 8 to set the media because rtp_engine only accepts TOS decimal values. chan_sip accepts columns 2, 7, or 8 and does any appropriate conversion/lookup, but it doesn't accept 5 or 6. > > USED FOR Cisco Type Prec. Level DSCP Binary DSCP Hex DSCP Decimal Diffserv/ > TOS Hex Diffserv/ TOS Dec. Not Used cs7 7 111XXX 40-4E Not Used cs6 6 > 110XXX 30-3E AUDIO ef 5 101110 2E 46 B8 184 cs5 5 101000 28 40 A0 > 160 > af43 4 100110 26 38 98 152 > af42 4 10010024 3690144 af41 4 100010 22 34 88 136 cs44100000 20 32 > 80 128 af33 3 011110 1E 30 78 120 af32 3 011100 1D 28 70 112 af31 3 > 011010 1A 26 68 104 SIP cs3 3 011000 18 24 60 96 > af23 2 010110 16 22 58 88 af22 2 010100 14 20 50 80 af21 2 010010 > 12 18 48 72 cs2 2 010000 10 16 40 64 af13 1 001110 0E 14 38 56 af12 1 > 001100 0D 12 30 48 af11 1 001010 0A 10 28 40 cs1 1 001000 08 8 20 32 > DATA be 0 000000 00 0 0 0 > Precedence Values: > 7 Reserved 6 Routing 5 Voice 4 Streaming Video 3 Call Signalling 2 > Transactional 1 Bulk Data 0 Best Effort > > > > On Mon, Feb 10, 2014 at 11:23 AM, Jonathan Rose <[email protected]> wrote: > >> I've been looking into this issue and researching how TOS became the >> DiffServ field, but there are some issues with changing configuration >> options during a release that we feel the community needs to have some >> input on. We have a few options for going forward here, and some are more >> disruptive to existing configurations than others. >> >> 1. We can change the names of the fields and correct the behavior so that >> all values set for pjsip.conf are DSCP values. In this case, 'tos' becomes >> 'dscp' while 'tos_audio' and 'tos_video' become 'dscp_audio' and >> 'dscp_video' respectively. Databases and the alembic scripts we supply for >> building them would need to add the new fields. This change would certainly >> break existing configurations if we don't alias the TOS fields. If we do >> alias the TOS fields, then people expecting the current behavior will >> likely have QOS values that don't reflect their expectations. It's an >> obscure problem that would probably go unnoticed for a while. >> >> 2. We can have the 'tos' value for transports be set correctly by >> dropping the ECN portion (bits 7 and 8) and have the remaining 6 bits form >> the DSCP value so that it is being set as a TOS value would be. The >> benefit here is that this would require no significant changes on the >> configuration end while still being more or less accurate to what the >> settings are. We would probably want to display a warning message >> indicating that the field doesn't have support for the ECN bits if a value >> is supplied that includes them. In this scenario, 'tos_audio' and >> 'tos_video' for endpoints could be left alone and remain functioning as >> they do in chan_sip. >> >> 3. We can leave the existing TOS values functioning in the TOS manner >> while adding DSCP values that override them if provided. This would require >> correcting the behavior of the 'tos' setting for transports while we leave >> 'tos_audio' and 'tos_video' in 12 and then adding options for 'dscp', >> 'dscp_audio', and 'dscp_video' to trunk. In trunk the TOS options would be >> considered deprecated (but still functional). This is probably the cleanest >> way to do it, but it's still a bit more disruptive (when Asterisk 13 gets >> rolled out anyway) than option 2. >> >> Another thing to consider is whether or not we want to add support for >> reading the TOS/DSCP values as strings. While this wouldn't break any >> existing pjsip.conf files, we would need to update the alembic scripts for >> changing the TOS values to be strings in databases and this would require a >> little effort in upgrades. This is another change that might be better left >> as trunk only. >> >> Personally, I favor options 2 and 3. If the community feels differently >> though, I'm open to other approaches. >> >> >> On Mon, Feb 3, 2014 at 11:24 AM, George Joseph < >> [email protected]> wrote: >> >>> >>> As I was playing around with TOS/COS in pjsip last week I noticed some >>> inconsistencies that I'd like to correct... >>> >>> There's a 'tos' parameter on the transport object but not only does it >>> actually set DSCP instead of TOS, it sets it in pjproject only and >>> therefore for signalling only. >>> >>> There are tos_audio and tos_video parameters on endpoint which do set >>> tos for the rtp engine but they don't accept hex or symbolic values as >>> chan_sip does. >>> >>> So, given that DSCP has been around for a while and that's what the >>> symbolic values represent anyway, Id like to do the following... >>> >>> In transport, rename tos and cos to dscp_sip and cos_sip respectively >>> and for dscp_sip, create a new function ast_str2dscp() as a companion to >>> the existing ast_str2tos that resolves the symbolics. The new function is >>> needed because while the existing ast_str2tos function takes in a string >>> representation of DSCP, it left-shifts it 2 bits to go into the >>> rtp_engine's tos field. pjproject only accepts dscp. >>> >>> In endpoint, rename tos_audio and tos_video to dscp_audio and dscp_video >>> respectively, then use ast_str2tos to resolve the symbolics. >>> >>> I could also add the new parameters and leave the old ones there for >>> backwards compatibility for a while if that makes sense. >>> >>> What do you think? >>> https://issues.asterisk.org/jira/browse/ASTERISK-23235 >>> >>> >>> >>> >>> >>>
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