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diff --git a/trunk/doc/tex/qos.tex b/trunk/doc/tex/qos.tex new file mode 100644 index 000000000..acbf7f443 --- /dev/null +++ b/trunk/doc/tex/qos.tex @@ -0,0 +1,135 @@ +\subsubsection{Introduction} + +Asterisk support different QoS settings on application level on various protocol +on any of signaling and media. Type of Service (TOS) byte can be set on +outgoing IP packets for various protocols. The TOS byte is used by the network +to provide some level of Quality of Service (QoS) even if the network is +congested with other traffic. + +Also asterisk running on Linux can set 802.1p CoS marks in VLAN packets for all +used VoIP protocols. It is useful when you are working in switched environment. +In fact asterisk only set priority for Linux socket. For mapping this priority +and VLAN CoS mark you need to use this command: + +\begin{verbatim} +vconfig set_egress_map [vlan-device] [skb-priority] [vlan-qos] +\end{verbatim} + +In table behind shown all voice channels and other modules of asterisk, that +support QoS settings for network traffic and type of traffic which can have +QoS settings. + +\begin{verbatim} + Channel Drivers ++==============+===========+=====+=====+=====+ +| | Signaling |Audio|Video| Text| ++==============+===========+=====+=====+=====+ +|chan_sip | + | + | + | + | +|--------------+-----------+-----+-----+-----+ +|chan_skinny | + | + | + | | +|--------------+-----------+-----+-----+-----+ +|chan_mgcp | + | + | | | +|--------------+-----------+-----+-----+-----+ +|chan_unistim | + | + | | | +|--------------+-----------+-----+-----+-----+ +|chan_h323 | | + | | | +|--------------+-----------+-----+-----+-----+ +|chan_iax2 | + | ++==============+=============================+ + Other ++==============+=============================+ +| dundi.conf | + (tos setting) | +|--------------+-----------------------------+ +| iaxprov.conf | + (tos setting) | ++==============+=============================+ +\end{verbatim} + + +\subsubsection{IP TOS values} + +The allowable values for any of the tos* parameters are: +CS0, CS1, CS2, CS3, CS4, CS5, CS6, CS7, AF11, AF12, AF13, AF21, AF22, AF23, +AF31, AF32, AF33, AF41, AF42, AF43 and ef (expedited forwarding), + +The tos* parameters also take numeric values. + +Note, that on Linux system you can use ef value in case your asterisk is running +from a user other then root only when you have compiled asterisk with libcap. + +The lowdelay, throughput, reliability, mincost, and none values are removed +in current releases. + +\subsubsection{802.1p CoS values} + +As far as 802.1p uses 3 bites from VLAN header, there are parameter can take +integer values from 0 to 7. + +\subsubsection{Recommended values} +Recommended values shown above and also included in sample configuration files: +\begin{verbatim} ++============+=========+======+ +| | tos | cos | ++============+=========+======+ +|Signaling | cs3 | 3 | +|Audio | ef | 5 | +|Video | af41 | 4 | +|Text | af41 | 3 | +|Other | ef | | ++============+=========+======+ +\end{verbatim} + +\subsubsection{IAX2} + +In iax.conf, there is a "tos" parameter that sets the global default TOS +for IAX packets generated by chan\_iax2. Since IAX connections combine +signalling, audio, and video into one UDP stream, it is not possible +to set the TOS separately for the different types of traffic. + +In iaxprov.conf, there is a "tos" parameter that tells the IAXy what TOS +to set on packets it generates. As with the parameter in iax.conf, +IAX packets generated by an IAXy cannot have different TOS settings +based upon the type of packet. However different IAXy devices can +have different TOS settings. + +\subsubsection{SIP} + +In sip.conf, there are three parameters that control the TOS settings: +"tos\_sip", "tos\_audio", "tos\_video" and "tos\_text". tos\_sip controls +what TOS SIP call signaling packets are set to. tos\_audio, tos\_video +and tos\_text controls what TOS RTP audio, video or text accordingly +packets are set to. + +There are four parameters to control 802.1p CoS: "cos\_sip", "cos\_audio", +"cos\_video" and "cos\_text". It behavior the same as written above. + +\subsubsection{Other RTP channels} + +chan\_mgcp, chan\_h323, chan\_skinny and chan\_unistim also support TOS and +CoS via setting tos and cos parameters in correspond to module config +files. Naming style and behavior same as for chan\_sip. + +\subsubsection{Reference} + +IEEE 802.1Q Standard: +\url{http://standards.ieee.org/getieee802/download/802.1Q-1998.pdf} +Related protocols: IEEE 802.3, 802.2, 802.1D, 802.1Q + +RFC 2474 - "Definition of the Differentiated Services Field +(DS field) in the IPv4 and IPv6 Headers", Nichols, K., et al, +December 1998. + +IANA Assignments, DSCP registry +Differentiated Services Field Codepoints +\url{http://www.iana.org/assignments/dscp-registry} + +To get the most out of setting the TOS on packets generated by +Asterisk, you will need to ensure that your network handles packets +with a TOS properly. For Cisco devices, see the previously mentioned +"Enterprise QoS Solution Reference Network Design Guide". For Linux +systems see the "Linux Advanced Routing \& Traffic Control HOWTO" at +\url{http://www.lartc.org/}. + +For more information on Quality of +Service for VoIP networks see the "Enterprise QoS Solution Reference +Network Design Guide" version 3.3 from Cisco at: +\url{http://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/ccmigration\_09186a008049b062.pdf} |