Which statement is true about the IntServ QoS model?
A.
QoS traffic flows are managed on a hop-by-hop basis.
B.
QoS traffic flows are guaranteed end-to-end.
C.
QoS policies are not implemented, relying on best-effort delivery of packets.
D.
QoS policies require that traffic be divided into classes.
Explanation:
Integrated services (IntServ) is the name given to QoS signaling. QoS signaling allows an end station (or network node, such as a router) to communicate with its neighbors to request specific treatment for a given traffic type. This type of QoS allows for end-to-end QoS in the sense that the original end station can make a request for special treatment of its packets through the network, and that request is propagated through every hop in the packet’s path to the destination. True end-to-end QoS requires the participation of every networking device along the path (routers, switches, and so forth), and this can be accomplished with QoS signaling.
In 1994, RFC 1633 first defined the IntServ model. The following text, taken from RFC 1633, provides some insight as to the original intent of IntServ:
We conclude that there is an inescapable requirement for routers to be able to reserve resources, in order to provide special QoS for specific user packet streams, or “flows”. This in turn requires flow-specific state in the routers, which represents an important and fundamental change to the Internet model.
As it turns out, the requirement was not as inescapable as the engineers who authored RFC 1633 originally thought, as evidenced by the fact that the Internet still relies almost entirely on BE delivery for packets.