cs 447 networks and data communication department of computer science southern illinois university...
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CS 447 Networks and Data Communication
Department of Computer ScienceSouthern Illinois University Edwardsville
Fall, 2013
Dr. Hiroshi FujinokiE-mail: [email protected]
Frame Relay Networks
FrameRelay-Intro/000
CS 447 Networks and Data Communication
What is “Frame Relay”?
• Frame Relay (FR) is a VC (Virtual Circuit) data transmission network
• FR evolved from X.25 VC packet-switching network
• FR was introduced with two primary motivations:
Provide inexpensive virtual WAN network for corporate users
(i) Security (dedicated network for high security)
(ii) Speed (high volume data transmission in a short time)
(iii) Low cost (branch-to-branch long distance connection at low price)
Low delay data transmission for real-time voice transmission
- Eliminate point-to-point error control from X.25
(i), (ii) (iii) in a trade-off relationship
FrameRelay-Intro/001
CS 447 Networks and Data Communication
What is “Frame” in “Frame Relay”?
PacketSwitching
FrameRelay
CellRelay
CircuitSwitching
• Variable size• Large data units
• Variable size• Large data units
• Fixed size
• Small units• Continuous stream
• No “packet”
Public analogTelephone networks
ATM Frame Relay IP Networks
• Reserved (dedicated) resources• Expensive• Low variance in delay
• High quality
• Shared resources• Inexpensive• High variance in delay
• Low quality (best-Effort)
FrameRelay-Intro/002
CS 447 Networks and Data Communication
Low delay transmission in Frame Relay
X.25 VC Packet Switching
A/D D/A A/DD/A D/A A/D
Frame Relay
Digital TxAnalog Tx
D/A Digital to Analog Converter
A/D Analog to Digital Converter
High error rate High error rate
Fix Errors Fix Errors
Low error rate Low error rate
FrameRelay-Intro/003
CS 447 Networks and Data Communication
Low delay transmission in Frame Relay
• Error Control• Flow Control• Switching
• Error Control• Flow Control• Switching
X.25 VC Packet Switching
For human conversationthis delay < 400ms
FrameRelay-Intro/004
CS 447 Networks and Data Communication
Low delay transmission in Frame RelayFrame Relay
• Switching
• Switching
• Switching
• Switching
Short RTT delay
FrameRelay-Intro/005
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
Branch A
Branch B
Branch E
Branch C
Branch D
FrameRelay-Intro/006
Problem Scalability
N(N-1)
2links required
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
Branch A
Branch B
Branch E
Branch C
Branch D
FrameRelay-Intro/007
Problem Single point of network disconnection
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
Branch A
Branch B
Branch E
Branch C
Branch D
Dedicated Subscriber Loop
A long distance carrierWAN network
VC1
FrameRelay-Intro/008
Contract to a long distance carrier
You install onlythe subscriber loops
Problem Developing a nation-wide is too expensive
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
Branch A
Branch B
Branch E
Branch C
Branch D
Dedicated Subscriber Loop
A long distance carrierWAN network
VC2
FrameRelay-Intro/009
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
Branch A
Branch B
Branch E
Branch C
Branch D
Dedicated Subscriber Loop
A long distance carrierWAN network
VC3
FrameRelay-Intro/010
CS 447 Networks and Data Communication
Inexpensive virtual WAN network
What is VC supposed to do?
- No matter how busy the network is, your paid quota should be reserved
- Called CIR (Committed Information Rate)
- You pre-define VCs
- No need for creating VCs when you transmit data
Provide guaranteed transmission rate
Preserve pre-defined VCs
Short end-to-end delay transmission
- All resources are reserved
- Upper bound for end-to-end is also guaranteedFrameRelay-Intro/011
CS 447 Networks and Data Communication
Data Network
Circuit Switching
Packet Switching
Virtual Circuit
Datagram
X.25
ARPANET
Frame Relay
IP Network
Today’s Topic
FrameRelay-Intro/012
CS 447 Networks and Data Communication
1. IP Network (Store & Forward transmission)
Router
Data Packet
ACK
Data Packet Data Packet Data Packet
ACK ACK ACK
Transmitter Receiver
R1 R2 R3
2. Frame Relay (Forward without ACK)
Router
Data Packet
ACK
Data Packet Data Packet Data Packet
ACK ACK ACK
R1 R2 R3
FrameRelay-Intro/013
CS 447 Networks and Data Communication
Router Operation for IP Network (Store and Forward)
Router
Memory Buffer
Incoming Link Outgoing Link Store
Perform:• Switching• Error Check (CRC Check Sum)• Flow Control
Forward
ACK
FrameRelay-Intro/014
CS 447 Networks and Data Communication
Router Operation for Frame-Relay Network
Router
Temporary Buffer
Incoming Link Outgoing Link Store
Perform: Switching
Forward
Cut-throughAfter switching
FrameRelay-Intro/015
CS 447 Networks and Data Communication
Frame Relay Data Transfer (Forward without ACK)
Router
Data Packet Data Packet Data Packet Data Packet
ACK ACK ACK ACK
R1 R2 R3
Data as a collection of frames
ACK (= Error/Flow Control) Messages
Intermediate routers just relay frames and ACK messagesbetween two end hosts
FrameRelay-Intro/016
CS 447 Networks and Data Communication
Router Operation for IP Network (Store and Forward)
Network Layer
Link Layer
Physical Layer
Packeting Routing
Framing
Transmission Receiving
StoringError Check
Flow Control
De-Framing
Routing
FramingStoring
Transmission
Application
Transmitting Host First-Hop Router
Memory Copy
FrameRelay-Intro/017
CS 447 Networks and Data Communication
Router Operation for Frame Relay
Network Layer
Link Layer
Physical LayerTransmission Receiving
StoringFraming
Application
Transmitting Host
Memory Copy
Transmission
Routing
First-Hop RouterFrameRelay-Intro/018
CS 447 Networks and Data Communication
LAN A
LAN B
LAN C
LAN D
LAN E
Frame RelayNetwork
Frame Relay Router
Frame Relayas a network backbone
FrameRelay-Intro/019
CS 447 Networks and Data Communication