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diff --git a/doc/qos.tex b/doc/qos.tex new file mode 100644 index 000000000..c4d06e8de --- /dev/null +++ b/doc/qos.tex @@ -0,0 +1,119 @@ +\subsubsection{Introduction} + +Asterisk can set the Type of Service (TOS) byte 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 +enviropment. For maping skb->priority and VLAN CoS mark you need to use +command "vconfig set_egress_map [vlan-device] [skb-priority] [vlan-qos]". + +\subsubsection{SIP} + +In sip.conf, there are three parameters that control the TOS settings: +"tos\_sip", "tos\_audio" and "tos\_video". tos\_sip controls what TOS SIP +call signalling packets are set to. tos\_audio controls what TOS RTP audio +packets are set to. tos\_video controls what TOS RTP video packets are +set to. + +There are four parameters to control 802.1p CoS: "cos\_sip", "cos\_audio", +"cos\_video" and "cos\_text". It's behavior the same as writen above. + +There is a "tos" parameter that is supported for backwards +compatibility. The tos parameter should be avoided in sip.conf +because it sets all three tos settings in sip.conf to the same value. + +\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{H.323} +Also support TOS and CoS. + +\subsubsection{MGCP} +Also support TOS and CoS. + +\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. + +The lowdelay, throughput, reliability, mincost, and none values are +deprecated because they set the IP TOS using the outdated "IP +precedence" model as defined in RFC 791 and RFC 1349. They still +work in this version of Asterisk, but will be removed in future releases. + +\subsubsection{802.1p CoS values} + +As 802.1p uses 3 bites from VLAN header, there are parameter can take +integer values from 0 to 7. + + +\begin{verbatim} +=========================================== +Configuration Parameter Recommended +File Setting +------------------------------------------- +sip.conf tos\_sip cs3 +sip.conf tos\_audio ef +sip.conf tos\_video af41 +sip.conf tos\_text af41 +sip.conf cos\_sip 4 +sip.conf cos\_audio 6 +sip.conf cos\_video 5 +sip.conf cos\_text 0 +------------------------------------------- +iax.conf tos ef +iax.conf cos 6 +------------------------------------------- +iaxprov.conf tos ef +------------------------------------------- +mgcp.conf tos ef +mgcp.conf cos 6 +------------------------------------------- +h323.conf tos ef +h323.conf cos 6 +=========================================== +\end{verbatim} + +\subsubsection{Reference} + +IEEE 802.1Q Standard: +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 +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 +<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: + +<http://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/ccmigration\_09186a008049b062.pdf> + |