CS 447 Networks and Data Communication Department of Computer Science Southern Illinois University Edwardsville Fall, 2013 Dr. Hiroshi Fujinoki 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”? Packet Switching Frame Relay Cell Relay Circuit Switching Variable size Large data units Variable size Large data units Fixed size Small units Continuous stream No “packet” Public analog Telephone 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/D D/A A/D Frame Relay Digital Tx Analog Tx D/A Digital to Analog Converter A/D Analog to Digital Converter High error rate Fix Errors 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 conversation this delay < 400ms FrameRelay-Intro/004

CS 447 Networks and Data Communication Low delay transmission in Frame Relay Frame Relay 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 ProblemScalability N(N-1) 2 links 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 carrier WAN network VC 1 FrameRelay-Intro/008 Contract to a long distance carrier You install only the subscriber loops ProblemDeveloping 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 carrier WAN network VC 2 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 carrier WAN network VC 3 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 guaranteed FrameRelay-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 R1R2 R3 2. Frame Relay (Forward without ACK) Router  Data Packet  ACK  Data Packet  Data Packet  Data Packet  ACK  ACK  ACK R1R2R3 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-through After 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 R1R2R3 Data as a collection of frames ACK (= Error/Flow Control) Messages Intermediate routers just relay frames and ACK messages between 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 Storing Error Check Flow Control De-Framing Routing Framing Storing 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 Layer Transmission Receiving Storing Framing Application Transmitting Host Memory Copy Transmission Routing First-Hop Router FrameRelay-Intro/018

CS 447 Networks and Data Communication LAN A LAN B LAN C LAN D LAN E Frame Relay Network Frame Relay Router Frame Relay as a network backbone FrameRelay-Intro/019

CS 447 Networks and Data Communication