Red Hat Fedora 5 Unleashed

2017-07-07 02:10:07

The Foundation Summary is a collection of tables and figures that provides a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary might help you recall a few details. If you just read this chapter, this review should help solidify some key facts. If you are doing your final preparation before the exam, the following tables and figures are a convenient way to review the day before the exam.

Table 1-4. Layers of Data Communications
OSI Layer	Protocol Data Unit	Mechanism to Process PDU
7 (application)
6 (presentation)
5 (session)
4 (transport)	TCP segment	TCP port
3 (network)	Packet	Router
2 (data link)	Frame	Switch/bridge
1 (physical)

Table 1-5. Types of Network Services
Service Type	Location of Service	Extent of Traffic Flow
Local	Same segment/VLAN as user	Access layer only
Remote	Different segment/VLAN as user	Access to distribution layers
Enterprise	Central to all campus users	Access to distribution to core layers

Table 1-6. Comparison of Hierarchical Layers
Layer	Attributes
Access	High port density to connect to end users, low cost, uplinks to higher layers of the campus network, and Layer 2 services (traffic filtering, VLAN membership, and basic QoS)
Distribution	Aggregation of access-layer devices, high Layer 3 throughput, QoS features, security- and policy-based functions, and scalable and resilient high-speed links into the core and access layers
Core	Fast data transport, no "expensive" Layer 3 processing, redundancy and resiliency for high availability, and advanced QoS

Table 1-4. Layers of Data Communications

Table 1-5. Types of Network Services

Table 1-6. Comparison of Hierarchical Layers

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