Cisco Systems 8600 Series manual Protocol Stack Operation

Models: 8600 Series

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AIT/BTM Interworking and the ATM Protocol Stack

Figure 12-8 Protocol Stack Operation

Q.922 Fr Rly PDU

8

7

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2

1

 

 

 

 

 

 

 

 

 

 

 

 

 

FLAG

 

 

 

 

 

 

 

 

 

 

 

DLCI upper

 

 

 

 

 

CR

EA

 

 

 

 

 

 

 

 

DLCI lower

 

 

 

FECN

BECN

DE

EA

 

 

 

 

 

 

 

 

 

Data field

FLAG

8

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5

4

3

2

1

DLCI upper

 

 

FLAG

 

CR

EA

DLCI lower

 

 

FECN

BECN

DE

EA

FR-SSCS PDU

Data

Trailer

AAL5 PDU payload

CPCS PDU

N byte (1-65535)

PAD

0-47 byte

Length of user data

2 byte

CRC32

4 byte

SAR PDU

ATM PDU (adds in 5-byte header)

FFCI = ForeSight forward congestion indicator

48-byte PDU

48-byte PDU

...........

 

48-byte PDU

 

8

7

6

5

 

4

3

2

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HCF

 

 

 

 

 

VPI

 

 

 

 

 

00 = STI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VPI

 

 

 

VCI

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCI

 

 

 

Payload class

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5-byte

Congestion

FFCI

Re-

 

 

PTI

 

 

CLP

 

control

 

 

served

 

 

(payload type

 

 

(cell

 

header

 

 

 

 

 

 

 

 

(bursty

 

 

 

 

 

indicator)

 

 

loss

 

 

data)

 

 

 

 

 

 

 

 

prior-

 

 

 

 

 

 

 

 

 

 

 

ity)

 

 

 

 

 

HEC

 

 

 

 

 

 

 

 

 

 

48 data byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Physical

(line framing, coding, physical interface, etc.)

53-byte

ATM cell

53-byte

ATM cell

...........

53-byte

ATM cell

S5242

Frame Relay to ATM Network and Service Interworking 12-9

Page 323
Image 323
Cisco Systems 8600 Series manual Protocol Stack Operation