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Answer

TOS significates "Type of service" and represents the 2nd byte in the IP datagramm. TOS usually refers to "Quality of Service" in packet networks.

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Traditionally, the first three IP precedence (-> RFC 791) bits were supposed to be used in TOS Application Routing (RFC 1583-> OSPF, IS-IS) but no application really supports it. The TOS field has then been redefined as the Differentiated Services Code Point (DSCP-> RFC 2474) which consists of the first 6 bits and 2 bits used for a TCP mechanism called Explicit Congestion Notification (ECN) defined in RFC 3168.

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The value 160 (Binary 10100000) means IP precedence 5 (Binary 101) or DSCP Class Selector 5 (Binary 101000 = 0x28).
In order to obtain low-delay, low-jitter, low-loss service Expedited Forwarding should be used instead (= 184):

IP PrecIP Prec BinDSCP ClassDSCP BinDSCP HexDCSP DecTOS value (snom)
0000Best Effort0000000x0000
1001CS 10010000x08832
AF11-Low0010100x0A1040
AF12-Medium0011000x0C1248
AF13-High0011100x0E1456
2010CS 20100000x101664
AF21-Low0100100x121872
AF22-Medium0101000x142080
AF23-High0101100x162288
3011CS 30110000x182496
AF31-Low0110100x1A26104
AF32-Medium0111000x1C28112
AF33-High0111100x1E30120
4100CS 41000000x2032128
AF41-Low1000100x2234136
AF42-Medium1001000x2436144
AF43-High1001100x2638152
5101CS 51010000x2840160
Expedited Fwdg1011100x2E46184


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Antwort

TOS bedeutet "Type of Service" und stellt das 2. Byte im IP-Datagramm dar. TOS bezieht sich in der Regel auf "Quality of Service" in Paketnetzen.

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Traditionell sollten die ersten drei IP-Präzedenzbits (-> RFC 791) im TOS Anwendungs-Routing (RFC 1583-> OSPF, IS-IS) verwendet werden, aber keine Anwendung unterstützt dies wirklich. Das TOS-Feld wurde dann als Differentiated Services Code Point (DSCP-> RFC 2474) neu definiert, der aus den ersten 6 Bits besteht und 2 Bits, die für einen TCP-Mechanismus namens Explicit Congestion Notification (ECN) verwendet werden, der in RFC 3168 definiert ist.

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Der Wert 160 (Binär 10100000) bedeutet IP-Präzedenz 5 (Binär 101) oder DSCP Klassenselektor 5 (Binär 101000 = 0x28).
Um einen verzögerungsarmen, jitter- und verlustarmen Dienst zu erhalten, sollte stattdessen Expedited Forwarding verwendet werden (= 184):

IP PrecIP Prec BinDSCP KlasseDSCP BinDSCP HexDCSP DecTOS Wert (Snom)
0000Best Effort0000000x0000
1001CS 10010000x08832
AF11-Low0010100x0A1040
AF12-Medium0011000x0C1248
AF13-High0011100x0E1456
2010CS 20100000x101664
AF21-Low0100100x121872
AF22-Medium0101000x142080
AF23-High0101100x162288
3011CS 30110000x182496
AF31-Low0110100x1A26104
AF32-Medium0111000x1C28112
AF33-High0111100x1E30120
4100CS 41000000x2032128
AF41-Low1000100x2234136
AF42-Medium1001000x2436144
AF43-High1001100x2638152
5101CS 51010000x2840160
Expedited Fwdg1011100x2E46184


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