1. CSE 30264 Computer Networks Prof. Aaron Striegel Department of Computer Science & Engineering University of Notre Dame Lecture 20 – March 25, 2010

2. Today’s Lecture Project 3 –In-Class Exercise Network Issues –Quality of Service Spring 2010CSE 302642 Physical Data Network Transport Application

3. Spring 2009CSE302643 Quality of Service Outline Realtime Applications Integrated Services Differentiated Services

4. Spring 2009CSE302644 Realtime Applications Require “deliver on time” assurances –must come from inside the network Example application (audio) –sample voice once every 125us –each sample has a playback time –packets experience variable delay in network –add constant factor to playback time: playback point Microphone Speaker Sampler, A D converter Buffer, D A

5. Spring 2009CSE302645 Example Distribution of Delays

6. Spring 2009CSE302646 Integrated Services Service Classes –guaranteed –controlled-load Mechanisms –resource reservation (signalling) –admission control –policing –packet scheduling

7. Spring 2009CSE302647 Flowspec Rspec: describes service requested from network –controlled-load: none –guaranteed: delay target Tspec: describes flow’s traffic characteristics –average bandwidth + burstiness: token bucket filter –token rate r –bucket depth B –must have a token to send a byte –must have n tokens to send n bytes –start with no tokens –accumulate tokens at rate of r per second –can accumulate no more than B tokens

8. Spring 2009CSE302648 Per-Router Mechanisms Admission Control –decide if a new flow can be supported –answer depends on service class –not the same as policing Packet Processing –classification: associate each packet with the appropriate reservation –scheduling: manage queues so each packet receives the requested service

9. Spring 2009CSE302649 Reservation Protocol Called signalling in ATM Proposed Internet standard: RSVP Consistent with robustness of today’s connectionless model Uses soft state (refresh periodically) Designed to support multicast Receiver-oriented Two messages: PATH and RESV Source transmits PATH messages every 30 seconds Destination responds with RESV message Merge requirements in case of multicast Can specify number of speakers

10. Spring 2009CSE3026410 RSVP Example Sender 1 Sender 2 PATH RESV (merged) RESV Receiver B Receiver A R R R R R

11. Spring 2009CSE3026411 RSVP Associate packet with reservation (classifying): –source address, destination address, protocol number, source port, destination port Manage packets in queues (scheduling).

12. Spring 2009CSE3026412 RSVP versus ATM (Q.2931) RSVP –receiver generates reservation –soft state (refresh/timeout) –separate from route establishment –QoS can change dynamically –receiver heterogeneity ATM –sender generates connection request –hard state (explicit delete) –concurrent with route establishment –QoS is static for life of connection –uniform QoS to all receivers

13. Spring 2009CSE3026413 Differentiated Services Problem with IntServ: scalability Idea: segregate packets into a small number of classes –e.g., premium vs best-effort Packets marked according to class at edge of network Core routers implement some per-hop-behavior (PHB) Example: Expedited Forwarding (EF) –rate-limit EF packets at the edges –PHB implemented with class-based priority queues or WFQ

14. Spring 2009CSE3026414 DiffServ (cont) Assured Forwarding (AF) –customers sign service agreements with ISPs –edge routers mark packets as being “in” or “out” of profile –core routers run RIO: RED with in/out

15. Coding Form into small groups –Twist: Must sit by people who you did not work with on the project Spring 2010CSE 3026415 Build a simple UDP chat server

16. Write Threaded Code UDP Server –Step 1 Listen on port X (pass in via parameter) Read message / display on screen Spring 2010CSE 3026416

17. Write Threaded Code UDP Server –Step 1 Listen on port X (pass in via parameter) Read message / display on screen –Step 2 Keep track of incoming IP / ports Design –Local vs. global –struct vs. class Spring 2010CSE 3026417

18. Write Main Function main function –Step 1 Start up the thread Loop until input is QUIT! –Step 2 Send the typed text to all known other clients –Step 3 Allow adding of IP via syntax –ADDCLIENT 129.74.20.40 8908 –Step 4 Dump current client list via DUMPSTATUS Spring 2010CSE 3026418

19. Moment of Zen Spring 2010CSE 3026419