DATKO - WAN : PPP , FrameRelay , ATM , IP over ATM , IP over SONET / SDH

DATKO DATenKOmmunikation

WAN Protocols

( no warranty ) not yet ready

OSI Layer	PPP ( Point-to-Point )	FrameRelay	ISDN D Channel	ISDN B Channel	HDLC	SDLC	ATM	IP over SONET / SDH	Ethernet New (2001)	SMDS	X.25 ( out of date)
7.Application
6.Presentation
5.Session
4.Transport
3.Network	IP , IPX , ...	IP	DSS1 IP --> ( Q.931 )	IP			IP	IP	IP	SIP L3	X.25-PLP ( IP --> X.121 --> Link )
2.Data Link	PPP	LAPF	LAPD ( Q.921 )	PPP / HDLC / FR	HDLC	SDLC	AAL ATM-Layer	PPP	Ethernet 1Gbit/s 10GBit/s	SIP L2 ; DXI	LAPB ( X.25 Layer 2 )
1.Physical	Modem , T1 , ...	Modem , T1 , ...	I.430 , I.431			V.24 , V.35 , X.21	SONET , SDH	SONET , SDH	Fiber	SIP L1 DS1 , DS3 , ...	V.35 , RS232 , X.21 , X21.bis , ...
DATKO Home

Optical Carrier Networks based on DWDM (WDM) with MPLS / GMPLS

OSI Layer	IP over ATM / DWDM	IP with MPLS / DWDM	IP with GMLPS (2002)	IP with GMLPS (2003)
7.Application
6.Presentation
5.Session
4.Transport
3.Network	IP	IP	IP	IP
2.Data Link	ATM	MPLS	GMPLS	GMPLS
1.Physical	SDH/SONET DWDM	SDH/SONET DWDM	SDH/SONET DWDM and optical switching	DWDM and optical switching

Short Explanations

1. WAN Encapsulation Protocols
2. Data Link Layer WAN Protocols
3. Interfaces
4. WAN Options
5. IP over SONET / SDH (RFC 1619)
6. How does ATM Layers map to OSI reference model?
7. IP over ATM
8. HDLC , LAPD , LAPF , ...
9. Physical Layer
10. Ethernet in the WAN
11. Example : Router Interfaces

1. WAN Encapsulation Protocols :

Dedicated Point-to-Point : HDLC , PPP , LAPB
Packet Switched : FrameRelay , ISDN , X.25
Circuit Switched : ISDN D channel LAPD , ISDN B channel PPP , FrameRealy , X.25

2. Data Link Layer WAN Protocols :

PPP
FrameRelay
ISDN
HDLC

3. Interfaces :

DTE : Data Terminal Equipment ( on the user device )
DCE : Data Circuit-Terminating Equipment ( on the provider device )
( a modem has a DCE )

4. WAN Options :

/Network/LAN
/Network/WAN

/Network/WAN/Dedicated
/Network/WAN/Dedicated/Leased Lines ( E1, E3, ... T1, T3, .. )

/Network/WAN/Switched
/Network/WAN/Switched/Circuit/ISDN
/Network/WAN/Switched/Packet ( FrameRelay , X.25 )
/Network/WAN/Switched/Cell/ATM

5. IP over SONET / SDH (RFC 1619)

Mapping IP directly onto SONET links is being implemented to avoid the cell-header and the packet-to-cell mapping overhead imposed by ATM. This direct mapping uses a PPP-like (Point To Point Protocol) protocol. It transports nothing but IP. At each node, the IP packet is unwrapped from its PPP frame, the destination ip address is examined, the routing path is determined, and the packet is rewrapped in a new PPP frame and sent on its way to the destination.

6. How does ATM Layers map to OSI reference model?

Many people agree that the ATM standards cover 3 distinct layers -- Physical Layer, ATM Layer and ATM Adaptation Layer (AAL).

The Physical Layer (corresponding to OSI Physical Layer) is usually taken to be SONET / SDH. The OSI Physical Layer deals with medium-related issues, the ATM Physical Layer, too.

The ATM Layer is responsible for creating cells and formatting the cell header (5 octets). Therefore the ATM Layer corresponds to the OSI Data Link Layer (formatting, addressing, flow control, etc.). The AAL is responsible for adapting ATM's cell switching capabilities to the needs of specific higher layer protocols. The AAL is responsible for formatting the cells payload (48 bytes). Therefore the AAL corresponds like the ATM Layer to the OSI data link (data error control, above Physical).

I think that for our purpose, we need the OSI Layer 3 for IP. All this proves that the OSI model is an excellent model, but only a model we use as a basis for discussion and comparison services. ATM fits best for our purpose if we take two OSI Layers for ATM ( including SONET / SDH ), knowing that there are other models possible, too.

Joachim Datko

7. IP over ATM

/ATM
/ATM/Encapsulation (RFC 1483)
/ATM/Classical IP over ATM ( CIP )
/ATM/LAN Emulation ( LANE )
/ATM/Multiprotocol over ATM ( MPOA )

8 . HDLC , LAPD , LAPF , ... Rhys Haden

9. Physical Layer ( PDH ( non synchronous rates --> plesiochronous digital hierarchy ), SDH ( synchronous digital hierarchy ))

Terms:

OC-n Optical Carrier (Fundamental unit of SONET)
SONET Synchronous Optical NETwork
Synchronous Digital Hierarchy)
STM-1 Synchronous Transport Module, level 1 (starts at 155.52Mbps)
STS-1 Synchronous Transport Signal, level 1 (starts at 51.84Mbps)

Framing	Data Rate	Remarks

PDH

DS0 ( E0 )	64 kbps	1 64 kpbs channel
ISDN BR	144 kbps
DS1 ( T1 )	1.544 Mbps	ISDN PR , 23 B + 1 D channels
E1	2.048 Mbps	30 B + 2 D channels
DS2	6.314 Mbps	ADSL , 96
E2	8.448 Mbps	120
E3	34.368 Mbps	480
DS3 ( T3 )	44.376 Mbps	672
E4	139.246 Mbps	1920

SDH

STS-1 OC-1	51.84 Mbps
SONET STS3c OC-3 SDH STM1	155.52 Mbps
SONET STS12c OC-12 SDH STM4	622.08 Mbps
SONET STS48c OC-48 SDH STM16	2.48832 Gbps
SONET STS192c OC-192 SDH STM64	9.95328 Gbps

e.g. : A ISP needs in Germany 120 ISDN - channels:

4 x E1 --> 120 B channels for 120 simultan logins to an Internet Service Provider.

e.g. : A Company has a T3 Link between two Locations.

About this Link are 21 E1 or 28 T1 Connections possible ( ore a mix of E1 and T1 )

10. Ethernet in the WAN

With 1 GBit/s and 10 GBit/s ethernet will be the fasted WAN - protocol. The Quality of Service problem of ethernet is the only drawback for ethernet WAN-connections ( the standard for 10 GBit/s ethernet is awaiting for 2002 ).
Joachim Datko

11. Example : Router Interfaces

Packet over Sonet (POS) : STM-1, STM-4, STM-16
Packet over Sonet (POS) channelized : STM-1/STM-4 : E1 channel, 64k-channel
Gigabit Ethernet
Fast Ethernet
ATM : 155 Mbit/s , 622 MBit/s

Links :

WAN Protocols : T. Naugler
WAN Concepts : www.jaring.nmhu.edu
Juniper WAN Concepts : Transitioning from IP-over-LANE/ATM to IP/MPLS Networks

Connection Speeds