Voice And Telephony over ATM: Status Raj Jain The Ohio State University Columbus, OH 43210
[email protected] http://www.cis.ohio-state.edu/~jain/ March 1998 The Ohio State University 1
Raj Jain
Overview q q q
VTOA: Protocol Stack and Services AAL: AAL1, AAL5, New AAL2 Interworking Function m Signaling m Addressing m Timing and Synchronization Raj Jain
The Ohio State University
2
Voice over ATM: Issues ATM Network
q q q
q
Connection Setup Coding/decoding of voice in to bits Packing of digital bit stream into cells (AAL1 or AAL5) End-to-end transmission of cells (Trunking) Raj Jain
The Ohio State University
3
Why VOA? q
q
Single physical connection for voice, video, data Integrated management, maintenance, signaling ⇒ Reduced cost
Raj Jain
The Ohio State University
4
Protocol Reference Model DSS2 Q.2931
G.711
SAAL
AAL ATM Physical
q q q
AAL1 or AAL5. AAL5 required. One packet per cell 64 kbps PCM µ-law or A-law (G.711)
Raj Jain
The Ohio State University
5
VTOA Services q
q
N-ISDN m 64 kbps m 2×64 kbps m 384 kbps m 1536 kbps m 1920 kbps m Multirate N×64 kbps Analog m 3.1 kHz Voice m 7 kHz tones and announcements
The Ohio State University
6
Raj Jain
Supplementary Services Direct Dialing In (DDI) q Multiple Subscriber Number (MSN) q Caller Id Presentation q Caller ID Restriction q Connected Line ID Presentation q Connected Line ID Restriction q Subaddressing Note: All these are available from UNI 4.0 q
Raj Jain
The Ohio State University
7
ISO Supplementary Services q q q q q q q q
Name Id Call Transfer Call Diversion/forwarding Call Completion Call offer Call Intrusion Do Not Disturb Call Interception Raj Jain
The Ohio State University
8
AAL1 Sequence Number Convergence Sequence Sequence Sublayer Number Parity Count Indication Protection 1b q q
q q
3b
1b
3b
Payload 47B
Misordering bad ⇒ Sequence number Convergence Sublayer Indication (CSI) Used for clock synchronization Constant Bit Rate (CBR) Indication of lost or errored cells (Seq #) Raj Jain
The Ohio State University
9
AAL 1 Problems q q q q q
q
Fixed size (47B) payload Single user per VC No partial fill ⇒ Bandwidth Only 64k or N×64k No support for m Forward error correction m Compression (VBR), m Silence suppression, m Idle channel removal Not generally available
The Ohio State University
10
Raj Jain
AAL 5 q q q
Designed for data traffic No per cell length field, No per cell CRC One voice packet/cell ⇒ Payload = 8 to 40 bytes Common Common User Part PAD Part Length CRC-32 Payload Convergence Indicator Sublayer 1B 0-64kB 0-47B 1B 2B 4B
0
1 AAU bit in PTI indicates last cell Raj Jain
The Ohio State University
11
Delay q
q q q
q
48 bytes at 64 kbps = 6 ms ⇒ Need Echo cancellers 48 bytes at 16 kbps = 24 ms ⇒ too long Can't fill a cell completely Current AALs allow segmentation (long packets to multiple cells). Do not allow blocking (short packets in one cell) AAL Raj Jain
The Ohio State University
12
Low-Bit Rate Voice q
Time to fill 48-byte payload @8 kbps = 48 ms
ATM ATM Leased T1/E1 ATM Base ATM Cell Base Cell Switch Station Switch Station Assembler Assembler Dissembler Dissembler
Raj Jain
The Ohio State University
13
AAL2: History q
q q
Sept 95: T1S1.5 "Short Multiplexed AAL (SMAAL)" May 96: ITU-T started AAL-CU Feb 97: ITU-T Completed AAL2 (Record: 9 Months)
Raj Jain
The Ohio State University
14
AAL2 q q q q q
Ideal for low bit rate voice Variable/constant rate voice Multiple users per VC Compression and Silence suppression Idle channel suppression Payload 1
Payload 2
Payload 3
Pkt Pkt Pkt Payload 1 Payload 2 Payload 3 Hdr Hdr Hdr Cell Cell Header Header
Pkt Pkt Pkt Payload 1 Payload 2 Payload 3 Hdr Hdr Hdr Raj Jain
The Ohio State University
15
Protocol Structure q q
User 1
User 2
SSCS
SSCS
Layer Mgmt ANP
q
Common Part specification (CPS) AAL2 Negotiation procedure (ANP) Service Specific Convergence Sublayer (SSCS) Null for Mobile Voice. May have SSCS for Trunking User 3 SSCS
User n SSCS
CPS ATM Raj Jain
The Ohio State University
16
Cell Format q q q q q
STF: Start field = CPS PDU header OSF: Offset of the first packet SN: Sequence number mod 2, 0 or 1 P: Parity (odd) of start field Pad: Padding (0-47 bytes) Cell Header
OSF
S CPS CPS CPS P N Packet Packet Packet
Pad
STF
CID
LI UUI
HEC
Info Raj Jain
The Ohio State University
17
CPS Packet Format CID
LI UUI
8b 6b q
q q
5b
HEC
Info
5b
1-64B
Channel ID (CID): 0 = Not used, 1= Mgmt, 2-7=Reserved, 8-255=User ID Length (LI): 0-64, Default=45B User-to-User Indication (UUI): 0-27 = ID, 28-29=Resvd 30-31=OAM Raj Jain
The Ohio State University
18
Protocol Efficiency 16
16 10
Cell Header 5B
6 16
15
Start Field 1B
1 16 Pad 27 Fill Delay 32 kbps ADPCM 4 ms 32 kbps ADPCM 8 ms 64 kbps PCM 4 ms 64 kbps PCM 8 ms 64 kbps PCM 5.6 ms
CPS Header 3B Size 16 B 32 B 32 B 64 B 45 B
Efficiency 84% 91% 91% 96% 94% Raj Jain
The Ohio State University
19
AAL2: Status q q q q
q
Sept 97: I.363.2 approved Sept 97: Segmentation and reassembly I.366.1 frozen June 98: I.trunk to be frozen On-Going: m AAL2 negotiations procedures (ANP) m Operations, Administration and Maintenance (OAM) Future: Interworking with m Voice over IP m Voice over Frame Relay
The Ohio State University
20
Raj Jain
VTOA Desktop Desktop
Desktop Desktop
PBX PBX
IWF IWF
ISDN ISDN IWF IWF Desktop Desktop IWF IWF
ATM ATM Network Network (LAN, (LAN, WAN, WAN, or or Satellite) Satellite)
IWF IWF
PBX PBX
IWF ISDN IWF ISDN IWF Desktop IWF Desktop Legacy Legacy networks networks
Legacy Legacy networks networks
Raj Jain
The Ohio State University
21
ATM-ISDN Interworking q
q
One ATM connection per N-ISDN channel per call (Current) ATM signaling channel (VC=5) mapped to ISDN D channel ATM Private Public IWF Terminal ATM ISDN Private UNI UNI T or S/T ATM Private Terminal ATM Private UNI
Private ISDN
IWF PNNI
Q Raj Jain
The Ohio State University
22
IWF Functionality q q q q
User Plane Protocols Signaling: Control Plane Protocols Timing & Synchronization Addressing
Raj Jain
The Ohio State University
23
User Plane Protocols
G.711
G.711
AAL
AAL
ATM
ATM
ATM
Phy
Phy
Phy
B-TE Private B-ISDN SB
G.711
Phy
Phy
IWF
PNNI or TB
Phy
ISDN TE Q or T
T or S/T Raj Jain
The Ohio State University
24
Control Plane Protocols q q q q
Q.Sig Private N-ISDN (PSS1) Q.921+DSS1 Public N-ISDN SAAL+DSS2 Public B-ISDN PNNI Signaling Private B-ISDN DSS2
DSS2 DSS2
DSS2 DSS1
SAAL
SAAL SAAL
SAAL
ATM
ATM ATM
ATM
Phy
Phy
Phy
Phy
B-TE SB Private B-ISDN TB
DSS1
Q.921
Q.921
Phy
Phy
IWF
S/T Public ISDN Raj Jain
The Ohio State University
25
DSS2
DSS2 PNNI
PNNI PSS1
SAAL
SAAL SAAL
SAAL
ATM
ATM ATM
ATM
Phy
Phy
Phy
Phy
B-TE SB Private B-ISDN PNNI
Q.921
Q.921
Phy
Phy
DSS2 DSS2
DSS2 PSS1
SAAL
SAAL SAAL
SAAL
ATM
ATM ATM
ATM
Phy
Phy
Phy
B-TE SB Private B-ISDN TB
Q
IWF
DSS2
Phy
PSS1
Private ISDN PSS1
Q.921
Q.921
Phy
Phy
IWF
Q
Private ISDN Raj Jain
The Ohio State University
26
Q.2931 Signaling Setup Setup Setup Call Proceeding Call Proceeding Alerting Alerting Connect Connect
Call Proceeding Alerting Connect
Accept
Connect Ack Connect Ack
Connect Ack Raj Jain
The Ohio State University
27
Setup Mapping q
Terminate each protocol, or Map each message ATM
IWF
ISDN
Connect
Connect Connect Ack
Connect
Connect Connect Ack Raj Jain
The Ohio State University
28
Call Clear Mapping ATM
IWF
ISDN
Release Release Complete
Disconnect T305 Release Release Complete
Release
Disconnect
Release Complete T308
Release T308
Release Complete Raj Jain
The Ohio State University
29
Timing & Synchronization q q q
Phy based (Stratum 4) Adaptive (buffer fill based) Free-running ~
B-TE
ATM
~ IWF
ISDN
TE
Raj Jain
The Ohio State University
30
E.164 Numbers q
q q q q
q
North American Numbering Plan (NANP): 1(614)-555-1212 E.163 numbering plan for telephony: 12 digits E164 numbering plan for ISDN: 15 digits Defined in ITU-T recommendation E.164 for ISDN ISDN numbers uniquely identify interfaces to public networks Administered by public networks (Therefore, are not easily available for private network use) Raj Jain
The Ohio State University
31
ATM Addresses q
q
ATM Forum specifies three NSAP-like address formats: DCC Format, ICD Format,E.164 NSAP = Network Service Access Point Network supplied 39 47
Data Country Code (2B)
End System Not Used Supplied in Routing High-Order End System Selector DSP (10B) ID (6B) (1B)
International Code High-Order End System Selector Designator (2B) DSP (10B) ID (6B) (1B)
High-Order End System Selector 45 E.164 Number (8 B) DSP (4B) ID (6B) (1B) AFI Initial Domain Id
Domain Specific Part (DSP) Raj Jain
The Ohio State University
32
Addressing q
q
q q
Authority and Format Identifier (AFI) 39 = ISO DCC, 47 = British Standards Institute ICD, 45 = ITU ISDN Initial Domain Identifier (IDI). Domain Specific Part (DSP) ISDN uses E.164 numbers (up to 15 BCD digits) ATM forum extended E.164 addresses to NSAP format. E.164 number is filled with leading zeros to make 15 digits. Raj Jain
The Ohio State University
33
Addressing (Cont) q
q
q q
End System Identifier (ESI): 48-bit IEEE MAC address Selector is for use inside the host and is not used for routing. All ATM addresses are 20 bytes long. ATM forum removed the division of DSP into areas, etc.
Raj Jain
The Ohio State University
34
q
q
Private networks must support all three formats Type of Number field = Unknown Numbering Plan Indication field = ISO NSAP Public networks must support native E.164 and may optionally support three NSAP-encoded formats. For E.164: Type of Number field = International number Numbering Plan Indication field = Recommendation E.164
Raj Jain
The Ohio State University
35
NSAP is a Misnomer! NSAP = Network Service Access Point Identifies network layer service entry q SNPA = Subnetwork point of attachment Identifies the interface to subnetwork NSAP q SNPA address (or part of it) is used to carry the packet across the network. q CLNP uses NSAP to deliver the packet Network to the right entity inside the host. Datalink q ATM uses NSAP-like encoding Physical but ATM addresses identify SNPA and not NSAP. SNPA The Ohio State University Raj Jain q
36
Summary
q
q
q
Circuit emulation services for CBR using AAL1 or AAL5. ATM Trunking using AAL2 is being developed. Allows low bit rate VBR, multiple users/cell IWF has to deal with data forwarding, signaling, addressing, and clock synchronization. Raj Jain
The Ohio State University
37
References q
q
q
q
For a tutorials on VTOA, Signaling, and PNNI see: http://www.cis.ohio-state.edu/~jain/ ATM Forum, "Voice and Telephony over ATM to the Desktop," af-vtoa-0083.000, May 1997 ATM Forum, "Circuit Emulation Service Specification V2.0," af-vtoa-0078.000, January 1997. ATM Forum, "Dynamic Bandwidth Utilization in 65 kbps time-slot trunking over ATM- using CES," afvtoa-0085.000, July 1997 Raj Jain
The Ohio State University
38
q
q
q
q
q
ATM Forum, "ATM Trunking using AAL1 for Narrowband Services V1.0," af-vtoa-0089.00, July 1997 ATM Forum, "PNNI V1.0," af-pnni-0055.000, March 1996. ATM Forum, "UNI Signaling 4.0," af-sig-0061.000, July 1996. ITU-T, "B-ISDN ATM Adaptation Layer Specification: Type 2 AAL," I.363.2 ITU-T, "B-ISDN ATM Adaptation Layer Specification: Type 1 AAL," I.363.1, Aug 96.
Raj Jain
The Ohio State University
39
q
q
ITU-T, "B-ISDN ATM Adaptation Layer Specification: Type 5 AAAL," I.363.5, Aug 96. ITU-T, "General Arrangements for Interworking Between B-ISDN and 64 kb/s Based ISDN," I.580, March 1993.
Raj Jain
The Ohio State University
40
VOA Products q
q
q
GDC, "APEX Family of ATM Products," http://www.gdc.com/products/prod_atm_vsm.html Implements AAL2. Nortel, "Magellan Passport ATM Switch," VBR Voice. Not AAL2. CISCO, Stratacom ATM Switches, Not AAL2.
Raj Jain
The Ohio State University
41
Abbreviation AAL AAL-CU ADPCM ANSI ATM CBR CCS CES CID CPS ITU-T LI
ATM Adaptation Layer AAL Composit User Adaptive Differential Pulse Code Modification American National Standards Institute Asynchronous Transfer Mode Constant Bit Rate Common Channel Signaling Circuit Emulation Service Channel Identifier Common Part Sublayer International Telecommunications Union Telecommunications Sector Length Indicator Raj Jain
The Ohio State University
42
PCM PCR PDU SMAAL SSCS UUI VBR VTOA
Pulse Code Modulation Peak Cell Rate Protocol Data Unit Short Multiplexed AAL Service Specific Convergence Sublayer User-to-User Indication Variable Bit Rate Voice and Telephony over ATM
Raj Jain
The Ohio State University
43
Thank You!
Raj Jain
The Ohio State University
44
