QoS for the CCNA - the basics

When contracting a routed IP circuit for a university, a network analyst needs to ensure that quality of service requirements for some of its internal services are met. The contracted operator offers DiffServ contracts, which already include network control and OAM, but the contractor needs to specify the Per-Hop Behaviors (PHB) required to provide other services. According to RFC 4594, to handle telephony, signaling, multimedia conferences and Internet traffic, the analyst must indicate, respectively, for the contract with the operator, the following Differentiated Services Code Point (DSCP): reminder: Class of service: CS Standard CS0 (DF) Low-priority data CS1 Network operations, administration and management (OAM) CS2 Broadcast video CS3 Real-time interactive CS4 Signaling CS5 Network control CS6 Reserved for future use CS7 Expedited Forwarding (EF) has the characteristics of low delay, low loss and low jitter. suitable for voice, video and other realtime services. EF traffic is often given strict priority queuing above all other traffic classes. Expedite Forwarding - Class Selector 5 - Assured Forwarding 41, 42, 43 - Default Forwarding. Assured Routing 31, 32, 33 - Class Selector 5 - Assured Routing 41, 42, 43 - Standard Routing. Assured Forwarding 31, 32, 33 - Class Selector 4 - Expedited Forwarding - Standard Forwarding. Expedite Forwarding - Class Selector 4 - Assured Forwarding 41, 42, 43 - Class Selector 7. Assured Forwarding 31, 32, 33 - Class Selector 4 - Expedited Forwarding - Standard Forwarding.

A Differentiated Services (DiffServ) QoS implementation was established to prioritize end-to-end video conferencing traffic. As in this solution traffic is marked and classified along its entire path, the layer 2 frame was marked with a CoS (Class of Service) value equal to 4. In this context, mark the alternative with the corresponding DSCP value following the RFC 2474 and the value of the AF (Guaranteed Forwarding) category in the layer 3 packet, as this data must fall into the high discard precedence group. DSCP=38; AF=43. DSCP=36; AF=41. DSCP=34; AF=42. DSCP=28; AF=31. DSCP=30; AF=43.

The IPv4 protocol header has the 8-bit DS (Differentiated Services) field, which replaced the old ToS (Type of Service). DS is subdivided into 6-bit DSCP (Differentiated Services Code Point) and 2-bit ECN (Explicit Congestion Notification). One of the traffic classes encoded by DSCP is known as Expedited Forwarding. The characteristics of this class are related to applications of. voice, video transmission and real-time services. access to conventional websites, such as corporate systems and e-commerce. file transfers that can wait to complete, such as FTP or SFTP. sending and receiving emails. DNS name resolution.

The DiffServ architecture, which makes it possible to classify IPv4 datagrams according to the desired type of traffic through a value called DSCP (Differentiated Services Code Point), supports classifying a maximum number of traffic classes, equal to. 4 classes. 6 classes. 8 classes. 64 classes. 256 classes.

One of the fields in the IPv4 packet header is the 8-bit DiffServ (DS), formerly called Type of Service (ToS), used to determine the priority of each packet. Of these 8 bits, the. 5 bits from the left identify the DHCP value, used by QoS mechanisms to avoid congestion. Last 3 bits, on the right, are used as explicit congestion notification bits. 4 left bits identify the DSCP value, used by QoS mechanisms for congestion notification. 6 bits on the left identify the ECN value, used by Quality of Service mechanisms to prioritize sending packets. 6 bits from the left identify the DSCP value, used by Quality of Service (QoS) mechanisms.

DiffServ is a mechanism for classifying and managing network traffic and providing Quality of Service (QoS). In IPv4, DiffServ uses 6 bits that make up the Differentiated Services Code Point (DSCP) and which occupies the field called. TTL. Flow Label. COS. Traffic Class. TOS.

The Diffserv architecture is capable of providing QoS in IP networks. Regarding this architecture, consider the statements below. I - The Differentiated Services (DS) field in the IPv6 packet is marked with a specific binary standard called DSCP (DS Codepoint) and is used to indicate how routers should treat the packet in terms of QoS. II - The QoS treatment given to each packet, on each router in the network, is called Per Hop Behavior (PHB), and each router in a Diffserv domain has its own table for determining the PHB based on the DSCP of the packet. III - The set of traffic flows belonging to the same class of service is called, in the Diffserv nomenclature on MPLS, Behavior Aggregates (BA). Only the following statement(s) are correct: Class-of-service (CoS) processing for IPv6 traffic uses the IPv6 DiffServ code point (DSCP) value. The IPv6 DSCP value is the first six bits in the 8-bit Traffic Class field of the IPv6 header. The DSCP value is used to determine the behavior aggregate (BA) classification for the packet entering the network device. I. I , II. I , III. II , III. I, II , III.

The ToS (type of service) field in the IP protocol is used by the differentiated services architecture. Currently, it is defined as DSCP (diff serv code point). true. false.