TCP/IP Tutorial and Technical Overview - IBM Redbooks

Figure 8-15 shows the use of boundary and interior components for two DS
domains.
Figure 8-15 DS domain
A DS domain normally consists of one or more networks under the same
administration. This can be, for example, a corporate intranet or an Internet
service provider (ISP). The administrator of the DS domain is responsible for
ensuring that adequate resources are provisioned and reserved to support the
SLAs offered by the domain. Network administrators must use appropriate
measurement techniques to monitor if the network resources in a DS domain are
sufficient to satisfy all authorized QoS requests.
DS boundary nodes
All data packets that travel from one DS domain to another must pass a
boundary node, which can be a router, a host, or a firewall. A DS boundary node
that handles traffic leaving a DS domain is called an egress node and a boundary
node that handles traffic entering a DS domain is called an ingress node.
Normally, DS boundary nodes act both as an ingress node and an egress node,
depending on the traffic direction. The ingress node must make sure that the
packets entering a domain receive the same QoS as in the domain the packets
traveled before. A DS egress node performs conditioning functions on traffic that
is forwarded to a directly connected peering domain. The traffic conditioning is
done inside of a boundary node by a traffic conditioner. It classifies, marks, and
314 TCP/IP Tutorial and Technical Overview
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B I B I B
I
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B = Boundary Component
I = Interior Component
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