APC IP DSLAM User's Guide download pdf (Page 10)

EDA 1200 System Overview

Figure 3 ADSL and VDSL Protocol Stack

Further, the segmentation unit in VDSL (codeword) is larger than in ADSL (cell),

which gives a higher payload/header utilization ratio:

Table 1 ADSL and VDSL Segmentation

ADSL VDSL

Segmentation 53 Bytes (cell) 65 bytes (codeword)

Segmentation header 5 Bytes 1 Byte

Payload utilization

(maximum) per unit

90,6% 98,5%

Apart from the theoretical maximum utilization ratio, per segmentation unit, the

payload size of 64 Bytes in PTM is equal to a minimum Ethernet frame size.

This will result in less padding, on average, in PTM than in ATM.

2.1.1.2 Fiber

Fiber to the home uses Ethernet directly over the physical media. There is

no further segmentation, which reduces both the overhead and the needed

processing capacity. The EDA solution allows for both single- and multi-mode

fibers.

2.1.1.3 Cat5

Cat5 is an Ethernet connection. There is no further segmentation, which

reduces overhead and needed processing capacity. Cat5 can only be used

indoors, and has a reach of approximately 100 m. On the other hand, there is

no need for special termination in the Customer Premises Equipment (CPE).

Any off the shelf Ethernet product can be used as CPE.

2.1.1.4 Telephony

The different telephony drop technologies are based on different concepts, and

therefore offer different properties. The principle difference between the three

voice services offered by EDA 1200 is illustrated in Figure 4 on page 7.

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APC IP DSLAM User's Guide Page 10