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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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Intserv model end-to-end across a network containing one or more Diffserv<br />

regions.<br />

Intserv views the Diffserv regions as virtual links connecting Intserv-capable<br />

routers or hosts running Intserv. Within the Diffserv regions, the routers are<br />

implemented with specific PHB definitions to provide aggregate traffic control.<br />

The total amount of traffic that is admitted into the Diffserv region may be limited<br />

by a determined policy at the edges of the Diffserv network. The Intserv traffic<br />

has to be adapted to the limits of the Diffserv region.<br />

There are two possible approaches for connecting Intserv networks with Diffserv<br />

networks:<br />

► Resources within the Diffserv network or region include RSVP-aware devices<br />

that participate in RSVP signalling.<br />

► Resources within the Diffserv region include no RSVP signalling.<br />

In our sample (Figure 8-20), we describe the second configuration, because it is<br />

assumed to become the most current approach to use.<br />

hostA<br />

Intranet<br />

Intserv<br />

RSVP<br />

R1<br />

Figure 8-20 Integrated Services <strong>and</strong> RSVP using Differentiated Services<br />

This configuration consists of two RSVP-capable intranets that are connected to<br />

Diffserv regions. Within the intranets, there are hosts using RSVP to<br />

communicate the quantitative QoS requirements with a partner host in another<br />

intranet running QoS-aware applications.<br />

The intranets contain edge routers R1 <strong>and</strong> R4, which are adjacent to the Diffserv<br />

region interface. They are connected with the border routers R2 <strong>and</strong> R3, which<br />

are located within the Diffserv region.<br />

The RSVP signalling process is initiated by the service requesting application on<br />

the host (for example, hostA). Traffic control on the host can mark the DSCP in<br />

320 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong><br />

R2<br />

Internet<br />

Diffserv<br />

R3<br />

R4<br />

Intranet<br />

Intserv<br />

RSVP<br />

hostB

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