<Li> Integrated services ("IntServ") implements the parameterized approach . In this model, applications use the Resource Reservation Protocol (RSVP) to request and reserve resources through a network . </Li> <Li> Differentiated services ("DiffServ") implements the prioritized model . DiffServ marks packets according to the type of service they desire . In response to these markings, routers and switches use various queueing strategies to tailor performance to expectations . Differentiated services code point (DSCP) markings use the first 6 bits in the ToS field (now renamed as the DS Byte) of the IP (v4) packet header . </Li> <P> Early work used the integrated services (IntServ) philosophy of reserving network resources . In this model, applications used the Resource reservation protocol (RSVP) to request and reserve resources through a network . While IntServ mechanisms do work, it was realized that in a broadband network typical of a larger service provider, Core routers would be required to accept, maintain, and tear down thousands or possibly tens of thousands of reservations . It was believed that this approach would not scale with the growth of the Internet, and in any event was antithetical to the notion of designing networks so that Core routers do little more than simply switch packets at the highest possible rates . </P> <P> In response to these markings, routers and switches use various queuing strategies to tailor performance to requirements . At the IP layer, DSCP markings use the 6 bits in the IP packet header . At the MAC layer, VLAN IEEE 802.1 Q and IEEE 802.1 p can be used to carry essentially the same information . </P>

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