X.25 Features

1
X.25 Features

• STDM
• Low Speed but full error control
• Very efficient and reliable for small Data
  packets
• Virtual Circuits

X.25 and OSI Layers
Application . .
Application . .
X.25 Packet
X.25 Packet
X.25 Packet
LCN
LCN
Data Link
Data Link
Data Link
Physical
Physical
Physical
Frame Relay Features

• STDM
• High Speed (45 Mbps) but no error control
• Suitable for bursty transmission of Data traffic
• Virtual Circuits

Frame Relay and OSI Layers
Application . . .
Application . . .
VC
VC
Data Link
Data Link
Data Link
Physical
Physical
Physical
2
ATM

• It is a technology for transforming data to
  fixed size cells
• It provides for connection oriented
  communication
• It supports other higher level protocols
• It can combine Voice, Video and Data on the same
  transmission line

ATM Sub-layers
Convergence Sub layer
Application . . .
AAL ATM Adaptation Layer
SAR Segmentation Reassembly
Cell Switching
Data Link
Physical
Physical
ATM Service Classes and QOS
AAL 1 - AAL 2 - AAL 3/4 - AAL 5 -
Constant Bit Rate (CBR), Circuit Emulation
Service (CES) Voice and video Variable Bit Rate
(VBR-rt) Video Variable Bit Rate
(VBR-nrt) Broadcast video, Data Available Bit
Rate (ABR), Unspecified Bit Rate (UBR) Data
3
Frame Relay and ATM Services
SLA Service Level Agreements
Frame Relay - PVC CIR Committed Information
Rate Bc Committed Burst Size Tc Committed Time
interval Be Excess Burst Size
ATM - PVC PCR Peak Cell Rate SCR Sustained
Cell Rate CLR Cell Loss Ratio CTD Cell
Transfer Delay CDV - Cell Delay Variation MCR
Mean Cell Rate BT Burst Tolerance or MBS Max.
Burst Size
Traffic Characteristics CLR CTD and CDV
PCR SCR and MBS MCR
CBR Specified Specified Specified N/A N/A
VBR-rt Specified Specified Specified Specified
N/A
VBR-nrt Specified CTD only Specified Specified
N/A
ABR Specified Unspecified Specified N/A Specif
ied
UBR Unspecified Unspecified Specified N/A N/A
4
ISDN and B-ISDN
An ISDN is circuit switch application very
similar to regular voice communications. It is a
digital circuit on demand having 2 different
service classification BRI and PRI.

• B-ISDN is described in ITU-T Recommendations
  I.327. The capabilities of B-ISDN are
• Broadband
• ISDN (64 Kbps or nx64 Kbps)
• UNI signaling
• NNI signaling
• B-ISDN transmission is the objective of ATM.

Management Plane
User Plane
Control Plane
Higher Layers
AAL
ATM Layer Cell Switching
Physical Layer
B-ISDN Protocol Reference Model