ATM

1
ATM NETWORK
2
ATM Cell Structure
AAL
ATM Switch
ATM reference model
A T M
???????????? cell ??????
ATM V.S. OSI
????? ??????? ??? ATM
Connection Type
3
General About ATM

• ???????????????????????????????????????
• Packet Switching
• banwidth requirement
• resource allocation
• Time Division Multiplexing

4
General About ATM

• ATM Feature
• Error flow control
• Fixed cell size
• ??? ? cell ?????????????????????? virtual
  circuit ?????????????? ATM Switching
• IS Scalable and flexible
• ATM ????????????????????????????????? ?????
  video ??? data ????? network ????????

5
ATM Cell Format
6
ATM
Cell Header Format

• ??? interface ????????????? 2 ?????
  ??? User-Network Interfaces (UNI) ???
  Network-Node Interfaces (NNI)
• UNI ??? interface ??????????????????
  ATM endpoint ??? ATM switch
• NNI ??? interface ????????????????
  ATM ????????????????????????? ATM switch ??? 2
  ???

UNI
NNI
7
ATM
Cell Header Format
UNI
Cell
Structure
NNI
8
BACK
ATM
Cell Header Format
Cell
Structure
9
ATM MODEL
User Layer
Adaptation Layer
ATM Layer
Physical Layer
10
ATM MODEL
11
ATM MODEL
Physical Layer ??????? ?????????????? ?????????
?????????????? ????????????????????????
ATM Layer ?????????????????? header ????????
??????????????? header ????????????????????
12
ATM MODEL
ATM Adaptation Layer (AAL)
??????????????????????????????????? ATM
????????????????????????? ????????????????????????
?? ?????? higher layer
User Layer ??????????????????????? ???????????
????????????????????? ??? ATM Model
??????????????????
13
ATM Model V.S. OSI Model
14
ATM Adaptation Layer (AAL)

• ???? AAL ??????????????????? 2???? ???
• 1. Convergence Sublayer (CS) ???????????????????
  Protocol Data Unit (PDU)
• 2. Segmentation and Reassembly Sublayer(SAR)
• ????????????? PDU ????????????????????????????????
  ??????????? SAR header ??????????????? SAR -PDU
  ?????????????????????? ???
• Type
• Sequence number
• Multiplexing identifier

15
??????? AAL
AAL 1

• ?????? payload 47 bytes ??? cell

• Sequence Number(SN) ????????????????????????????
  ???????????????????????????????????
• Sequence Number Protection(SNP)
  ??????????????????????????????????????????????????
  ????????????????????????? 1 bit
  ?????????????????????????????? 2 bit

16
AAL 2

• payload ?????? 45 bytes ??? cell
• SN ?????????????????????????????????????????????
  ?????????????????????????
• Information Type (IT) ??????????????????????????
  ????(??????????????????,???????? ????????????)
• Length Indicator(LI)????????????????????????????
  ???????(0 ??? 45 byte)
• Cyclic-Redundancy-Check (CRC)???????????????????
  ?????????????????

17
AAL 3/4

• Payload ?????? 44 bytes ??? cell
• Segment Type (ST) ????????????????????????
• Sequence Number (SN) ???????????????????????
• MID ?????????????????????????????????????
• Length Indicator (LI) ??????????????????????????
  ????
• CRC ????????????????????????????????????

18
AAL 5

• Payload ?????? 48 bytes ??? cell

19

• CONNECTION TYPES
• Point-to-Point
• Point-to-Multipoint

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21
ATM Switch ????????? ?????? ATM
????????????????? 2 ?????? ??? 1.
???????????????????????????????? 2.
?????????????????????????? virtual circuit
?????????????????????????? ???????????????????????
?????????????????????? ???????????????????????????
?? ???????????? ???????????????????????????????
??? ????????????????????????????????????????
????????????
Cells come in Cells are switched Cells go
out
22
Cell destined Start for line 2 of
cycle 1
Start of cycle 2
Start of cycle 3
Start of cycle 4
23
Start of cycle 1 Start of cycle 2 Start of
cycle 3
24
ATM
???????????
???????????
?????????????????
25
???????????

• ???????????????????????????????????????
  ????????? ATM ????????????????????????
  ????????????????????????? 5 ????
  ???????????????????????????????????? TC ???? TC
  ????????????????????????????????????? (HEC
  Header Error Control) ???????????????????????????
  ??????????????????????????????????????????????????
  ?????????????????

26
???????????

• ??????????????????????? ????????????? TC
  ??????????????????????????????????????????????????
  ????? ??????????????????????????????
  ??????????????????????????????????????????? ATM

27
?????????????????

• ?????????????????? ATM ???????
  connection-oriented ????????????????????
  connection ???????????????????????????????????????
  ????? ????????????????????? ??????????????????????
  ?? connection
• ??????????????????????????????
• ???????????????????????????? 0
  ??????????????????????? 5
• ?????????????????????????????????????????????
  ????????????????????

28
Adventage
AND
Disadventage
29
3.??????????????? ?????????
4. ??????????????? ??????????????? ????????(LAN) ?
?????(WAN)
2. ???????????? ??? ?????????????
1.??????????? ????????????? ????????? ???????????
????????????? ????????
5.????? ????????? ?????? ??????
30
(No Transcript)
31
???????????? ?????????????????
Overhead
??????????????
32
?????????

• By..
• YING AAE BAS