CoS and DSCP are two important parameters that user used when implementing QoS. Class of Service or CoS is a value that exists within the VLAN tag at Layer 2 and is used to prioritize frames that traverse a trunk. Particular frames of specific VLANs are given priorities within that VLAN 802.1Q tag.

CoS (Class of Service): This is a 3-bit field found in an Ethernet frame’s VLAN tag (802.1Q). It’s used to prioritize traffic on LANs, especially for trunk links between switches. Precedence: This is part of the older TOS field in the IP header and uses the first 3 bits of the TOS byte.

Oct 11, 2012 · The DSCP is superior to CoS in most ways - it is retained end-to-end, has a finer granularity, can be easily used both by end hosts and intermediary devices, and is an integral part of. That makes it the preferred place of QoS marking. However, there are protocols other than IP.

Differentiated services or DiffServ is a computer networking architecture that specifies a mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern IP networks.

CoS to DSCP mapping can be configured using the mls qos commands. The CoS values range from 0 to 7, and the DSCP values can range from 0 to 63. Here's a simple example of a CoS to DSCP mapping configuration:

Table 6-1 lists the commonly used DSCP values described in RFC 2475. Table 6-2 lists the RFC 791 precedence values from least to most important. Flash - mainly used for Voice Signaling or for Video. Critical -mainly used for Voice RTP.

Class of service (COS or CoS) is a parameter used in data and voice protocols to differentiate the types of payloads contained in the packet being transmitted. The objective of such differentiation is generally associated with assigning priorities to …

Jan 7, 2014 · There is no such convertion from CoS -> DSCP. There is only a CoS -> DSCP Mapping. Let's use this example an IP phone will generate a voice packet which has CoS5/DSCP46. We need to keep in mind that CoS is Layer2 and DSCP is Layer3.

In this lesson, I’ll explain everything there is to know about the TOS byte, IP precedence, and DSCP values. Let’s take a look at the TOS byte: Above, you see the IP header with all its fields, including the TOS byte. Don’t mix up TOS (Type of Service) and COS (Class of Service).

Nov 10, 2010 · CoS is a L2 marking contained within an 802.1q tag,. The values for CoS are 0 - 7. DSCP is a L3 marking and has values 0 - 63. Switches use an internal DSCP value when moving traffic through the switch.