Page 81 - Optical Switching And Networking Handbook

04_200023_CH03/Batesx 1/17/01 9:42 AM Page 66

66 Chapter 3

The remaining 87 columns and 9 rows (783 bytes) are designated
as the synchronous payload envelope (SPE). Inside the SPE, an addi-
tional one column nine rows high (9 bytes) is set aside for path over-
head. This is shown in Figure 3-9. After the path overhead is set
aside, the resulting payload is 774 bytes. In these 774 bytes, the ser-
vices are then mapped into the frame. The STS-1 payload can carry
the following:
1 DS-3
7 DS-2s

21 E-1s
28 DS-1s

Combinations of these payloads are also allowable. Two columns
are reserved as fixed stuff columns; these are columns 30 and 59.
The remaining 756 bytes carry the actual payload.

TEAMFLY

Figure 3-9
The SPE

SPE: 87x 9 = 783 bytes

®
Team-Fly