Wednesday, January 4, 2012

CCDA 640-864 Official Cert Guide - Chapter 6 Summary


WAN Overview

WAN Defined



Cost and Usage

Enterprise WAN



WAN Connection Modules


WAN Interconnections

WAN Transport Technologies

WAN Comparison












WAN Design Methodology

By PPDIOO;
Analyzing the network requirements
Characterizing the existing network
Designing the topology

Application Requirements

Response Time - Response time measures the time between the client user request and the response from the server host.

Throughput - In network communications, throughput is the measure of data transferred from one host to another in a given amount of time.

Reliability - Reliability is the measure of a given application’s availability to its users.

Bandwidth Considerations:
Copper
Fiber
Wireless

WAN Link Categories:
Private
Leased
Shared

Optimizing Bandwidth Using QoS

            Queuing, Traffic Shaping, and Policing

Classification - Identifies and marks flow and provides priority to certain flows:
            NBAR - Network-Based Application Recognition
            CAR - Committed access rate
Congestion management - Mechanism to handle traffic overflow using a queuing algorithm:
The hardware queue uses the strategy of first in, first out (FIFO). The software queue schedules packets first and then places them in the hardware queue. Keep in mind that the software queue is used only during periods of congestion. The software queue uses QoS techniques such as priority queuing, custom queuing, weighted fair queuing, class-based weighted fair queuing, low-latency queuing, and traffic shaping and policing.
Link-efficiency mechanisms - Reduce latency and jitter for network traffic on low-speed links:
Link fragmentation and interleaving (LFI), Multilink PPP (MLP), and Real-Time Transport Protocol (RTP) header compression provide for more efficient use of available bandwidth.
Traffic shaping and policing - Avoids congestion by policing ingress and egress flows:
Traffic shaping and policing are mechanisms that inspect traffic and take an action based on the traffic’s characteristics, such as DSCP or IP precedence its set in the IP header.

Window Size - The window size defines the upper limit of frames that can be transmitted without getting a return acknowledgment (8192).

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