What is the number of bits of DSCP field?
DiffServ uses a 6-bit differentiated services code point (DSCP) in the 8-bit differentiated services field (DS field) in the IP header for packet classification purposes. The DS field replaces the outdated IPv4 TOS field.
What is the DSCP value for EF?
DSCP 46
The Expedited Forwarding (EF) model is used to provide resources to latency (delay) sensitive real-time, interactive traffic. The EF model uses one marking — DSCP 46.
What is DSCP EF PHB?
This RFC defines a very simple PHB (low latency, with a cap on bandwidth), and a single DSCP (EF) to represent it. Expedited forwarding simply states that a packet with the EF DSCP should minimize delay, jitter, and loss, up to a guaranteed bandwidth level for the class.
What is DSCP value QoS?
Quality of Service (QoS) DSCP Marking determines traffic classification for network data. This can be used to determine which network traffic requires higher bandwidth, has a higher priority, and is more likely to drop packets.
What is EF PHB?
Expedited forwarding (EF) guarantees that any packets that are marked with the recommended EF codepoint 46 (101110) receive the best treatment available on release to the network. EF forwarding is often compared to a leased line.
How does DSCP marking work?
Once a packet is identified, it is typically marked near the source of the traffic flow, allowing the packets to receive differentiated treatment. Marking is typically done at the Layer 3 IP header using the Differentiated Services Code Point (DSCP); LAN implementations use the Class of Service (COS) field.
What is PHB in QoS?
In Diffserv terminology, the forwarding behavior that is assigned to a DSCP is called the per-hop behavior (PHB). The PHB defines the forwarding precedence that a marked packet receives in relation to other traffic on the Diffserv-aware system.
What is PHB in DSCP?
What is the DSCP value of CS4 and AF41?
CS and AF values have different dscp values. CS4 is 32 the nearest next dscp value is AF41 which is 34 followed by AF42 (36) and AF43 (38).
What is the AF41 formula?
For example, AF41 gives you a formula of (8 * 4) + (2 * 1) = 34. • An overriding goal to provide PHBs that provide enough bandwidth for each class, with the ability to drop less important traffic, hoping to avoid dropping more important traffic, if congestion does occur. • A convention that provides 4 classes for queuing.
What do binary DSCP values mean?
The binary DSCP values imply the queuing class with the first 3 bits (bits 0 through 2), and the drop preference in the next two bits (bits 3 and 4). Queuing tools that operate only on IP precedence can still react to the AF DSCP values, essentially making the AF DSCPs backward compatible with non-DiffServ nodes for queuing, at least.
How many DSCP values are needed to mark an AF PHB?
• To mark these packets, 12 DSCP values are needed; the names of these values as start with “AF” (assured forwarding). NOTE RFC 2360 clarifies some of the meaning and terminology used with DiffServ. Technically, the AF PHB, according to RFC 3260, is actually four different PHBs—one for each class.