IP QUALITY OF SERVICE CATEGORY
One of the ways of ensuring good audio quality in the framework of VOIP is to use a QoS mechanism (QoS: Quality of Service) at IP protocol level.
Alcatel-Lucent VOIP products such as LIOE/TSC-LIOE/INT-IP/IP-Phones/UA-HUB and Poly-HUB etc. are assigned in an IP QoS Category.
The Quality of Service category is to be entered:
- for IP Phones and the INTIP B board (Remote IP): in the "IP DOMAIN" sub-object.
- for the LIOE, TSC_LIOE and INT-IP A boards: in the "ETHERNET PARAMETERS" sub-object (see SHELVES>BOARDS>ETHERNET PARAMETERS).
(Note: in versions previous to version 4.1, the TSC_LIOE and INT-IP A boards are given in the IP DOMAIN sub-object.)
If the DATA network has no QoS functions, all attributes must remain at their default values.
IP Quality of service Category ID
Index of the IP quality of service COS.
Quality of Service Category Name
802.1Q used
YES: 802. 1Q of IEEE is managed on the network.
NO by default
802.1p priority
0 = lowest user priority
5 = highest user priority (the packet will be routed as quickly as possible)
5 by default
VLAN ID
This attribute identifies the VLAN to which the frame belongs
0 signifies that no LAN identifiers are indicated in the frame.
2 methods:
- the VLAN ID is explicitly specified in the Ethernet frame: request the VLAN ID from the administrator,
- the IS administrator specifies the VLAN ID in the LAN exchange. Set the VLAN ID to 0.
0 by default
TOS/Diffserv
This attribute specifies the type of packet management to apply in the network nodes (the IETF RFC references are 2474 and 2598).
According to the type of use, the value to be entered is:
- TOS: use a value between 0 and 7 (corresponding to the DTR fields) (the best value is 5).
- service differentiation: use a value between 0 and 63 (the best decimal value for the voice is 46).
Default value: 0
The QoS mechanism consists in marking ("tagging") the VOIP frames in order to give them priority at the IP level with respect to other IP frames such as Data frames (client/server IT applications, file transfer, FTP, etc.).
The tagging of an IP frame is made possible by a TOS (Type Of Service) field contained in the IP frame header.
The TOS field represents a byte in the header of an IP frame and enables the use of two IP frame tagging mechanisms: "Precedence" or "DiffServ".
The TOS byte is composed as follows:
The TOS consists of 2 parts:
- the first one, significant, concerns the six first high-order bits,
- the second one, unused, concerns the two last low-order bits, this part is called CU "Currently Unused".
If "Precedence" QoS mechanism is used, only the three first high-order bits of TOS byte are used (Value between 0 and 7, recommended value: 5).
If "Differentiated Services" QoS mechanism is used, the six first high-order bits are used (Value between 0 and 63, recommended value : 46).
Calculation rule to be used
A specific procedure must be followed to manage correctly "Precedence" or "DiffServ" in OmniPCX 4400.
Example 1
The computer network manager uses the QoS "Precedence" mechanism with decimal value 5.
To set it up in OmniPCX 4400, you must:
- convert the decimal value to binary : 5 -> 101,
- as "Precedence" corresponds to the three first high-order bits of the six bits used in the TOS field, you must add 3 zeros to the previous result: 101000 ,
- convert 101000 to decimal => 40.
=> 40 is the value to be completed in the "TOS/diffServ" attribute.
Example 2
The computer network manager announces that in his routers/routers switches, the tagging intended for VOIP frames is B8.
As the value to be entered in OmniPCX 4400 is decimal, a conversion must be carried out as follows:
To set it up in OmniPCX 4400, you must:
- convert the hexadecimal value to binary: B8 -> 10111000,
- as the marking on IP uses only the six first bits in the TOS field, you must remove the two last zeros to the previous result: 101110,
- convert 101110 to decimal => 46.
=> 46 is the value to be completed in the "TOS/DiffServ" attribute.
UDP Lost
Reserved for specialists.
Link loss detection timeout, receive direction (no traffic or keepalive), transmission direction (not acknowledged frame after several attempts).
Default value:7
UDP Lost Reinit
Reserved for specialists.
TSC-IP reset timeout after link loss is detected.
It is possible to re-establish a new UA link during this timeout.
Default value:7
UDP Keep Alive
Reserved for specialists.
Default value: 15
SIP Diff. Service
SIP Lost
SIP Lost: Min 1 - Max 255. Default value 5
SIP Keep Alive
SIP Keep Alive: Min 1 - Max 255. Default value 30