TCP/IP Tutorial and Technical Overview - IBM Redbooks

2. HostA generates a RSVP PATH message, which describes the traffic offered
by the sending application.
3. The PATH message is sent over the intranet to router R1. Standard
RSVP/Intserv processing is done by the network devices within the intranet.
4. The PATH state is defined in the router R1, and is forwarded to the Router R2
in the Diffserv network.
5. The PATH message is ignored in the Diffserv network at R2 and R3. It is sent
to R4 in the intranet and to hostB.
6. When the PATH message is received by hostB, a RSVP RESV message is
built, indicating the offered traffic of a specific Intserv service type.
7. The RESV message is sent to the Diffserv network.
8. The Diffserv network transparently transmits the message to router R1.
9. In R1, the RESV message triggers admission control processing. This means
requested resources in the initial RSVP/Intserv request are compared to the
resources available in the Diffserv network at the corresponding Diffserv
service level. The corresponding service level is determined by the Intserv to
Diffserv mapping function. The availability of resources is determined by the
capacity defined in the SLA.
10.If R1 approves the request, the RESV message is admitted and is allowed to
be sent to the sender, hostA. R1 updates its tables with reduced capacity
available at the admitted service level on this particular transmit interface.
11.If the RESV message is not rejected by any RSVP node in the intranet, it will
be received at hostA. The QoS process interprets the receipt of the message
as an indication that the specified message flow has been admitted for the
specified Intserv service type. It also learns the DSCP marking, which will be
used for subsequent packets to be sent for this flow.
8.3.3 Configuration and administration of DS with LDAP
In a Differentiated Services network, the service level information must be
provided to all network elements to ensure correct administrative control of
bandwidth, delay, or dropping preferences for a given customer flow. All DS
boundary components must have the same policy information for the defined
service levels. This makes sure that the packets marked with the DS field receive
the same service in all DS domains. If only one domain in the DS network has
different policy information, it is possible that the data packets passing this
domain will not receive the service that was contracted in the SLA between client
and service provider.
Network administrators can define different service levels for different clients and
manually provide this information to all boundary components. This policy
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