1. 10/1/2015 1R. Smith - University of St Thomas - Minnesota CISC 370 - Class Today GradingGrading ExamExam Recap on ProxiesRecap on Proxies Internet PhonesInternet Phones RoutingRouting Quality of ServiceQuality of Service

2. Assignment 6 Missing plans from people?Missing plans from people? Grading – looking for ‘substance’Grading – looking for ‘substance’ –Architectural plan and assessment of impact If you didn’t get it back, hand it in againIf you didn’t get it back, hand it in again 10/1/2015 2R. Smith - University of St Thomas - Minnesota

3. Grading Current class median 88%Current class median 88% Options on weighting the examOptions on weighting the exam – I chose to spread the weight – class avg = 83.6 10/1/2015 3R. Smith - University of St Thomas - Minnesota

4. Exam Answers 1. All pretty obvious – do it with powers of 21. All pretty obvious – do it with powers of 2 –Errors: not using powers of 2 Specifying a fractional number of channelsSpecifying a fractional number of channels 2. Change something in 1 – calculate difference2. Change something in 1 – calculate difference –Errors: increased image size does NOT increase channels! 3. No problem3. No problem 10/1/2015 4R. Smith - University of St Thomas - Minnesota

5. More Answers 4. Looked for ‘parallel’ layers4. Looked for ‘parallel’ layers 5. Looked for different ones:5. Looked for different ones: –TCP/IP application = session/pres/app ISO –TCP network does ROUTING –TCP transport has UDP 6. Swapped pres/app layers6. Swapped pres/app layers –Errors: choosing the wrong stack 7. Partitioned7. Partitioned 8. a: rerouted queries; b) more traffic8. a: rerouted queries; b) more traffic 9. Replicated9. Replicated 10/1/2015 5R. Smith - University of St Thomas - Minnesota

6. 10/1/2015 6R. Smith - University of St Thomas - Minnesota Recap: Proxies and the Internet DNS query forwarding and proxyingDNS query forwarding and proxying Proxies for Web TrafficProxies for Web Traffic –Proxy protocols –“Transparent” redirected proxies Proxies for general trafficProxies for general traffic –Purely transparent proxies/Firewall application

7. 10/1/2015 7R. Smith - University of St Thomas - Minnesota Session Initiation Protocol/Phones The problem: how do we deal with mobility?The problem: how do we deal with mobility? Let’s come up with some ideas.Let’s come up with some ideas. Constraints:Constraints: –Fits into existing Internet architecture and security –More or less fits the existing cel phone business model Charge periodic fee for phone useCharge periodic fee for phone use Track individual usage and charge for extra useTrack individual usage and charge for extra use

8. 10/1/2015 8R. Smith - University of St Thomas - Minnesota Problems to solve Do phones have names or numbers?Do phones have names or numbers? Do phones have IP addresses? Permanent?Do phones have IP addresses? Permanent? How do we avoid single-point failures?How do we avoid single-point failures? How do we locate a phone “right now”?How do we locate a phone “right now”?

9. 10/1/2015 9R. Smith - University of St Thomas - Minnesota SIP Components –User agent Client, User Agent Server – elements that send requests (clients) or respond to requests (servers) –Redirect Server – Find the address of a called device –Proxy Server – routes requests to the right server to process them. Provides a ‘local’ place to make queries –Location Service – provides information about a callee’s possible locations: SIP address->IP mappings –Registrar – registers a SIP address as having an IP address SIP URI – looks like an e-mail addressSIP URI – looks like an e-mail address

10. 10/1/2015 10R. Smith - University of St Thomas - Minnesota SIP Diagram Call setup between two phones requires two servers and two proxies

11. 10/1/2015 11R. Smith - University of St Thomas - Minnesota Internet Addressing Review from last timeReview from last time Class A? B? C?Class A? B? C? Subnet masks?Subnet masks? Difference between “network address”Difference between “network address” –and “host address”

12. 10/1/2015 12R. Smith - University of St Thomas - Minnesota Autonomous Systems (AS) Networks managed by different entitiesNetworks managed by different entities –Each network is its own “AS” Each AS handles its own internal routingEach AS handles its own internal routing “Global” Internet routing is between ASes“Global” Internet routing is between ASes This makes the Internet a hierarchyThis makes the Internet a hierarchy –Chaos of the olden days of the ‘flat’ Internet Special router protocolsSpecial router protocols –ERP – exterior routing, usually BGP (Border Gateway Protocol) –IRP – interior routing

13. The Routing Problem You have a bunch of nodesYou have a bunch of nodes –They are interconnected with links You have messagesYou have messages –They arrive on one node, destined for another The Network Problem: find the shortest routeThe Network Problem: find the shortest route The Node problem: pick which link to useThe Node problem: pick which link to use 10/1/2015 13R. Smith - University of St Thomas - Minnesota

14. 10/1/2015 14R. Smith - University of St Thomas - Minnesota Routing Protocols Distance vector protocolsDistance vector protocols –Oldest approach, ARPANET in 1969 –RIP – Routing Improvement Protocol Internet protocol that uses distance vectorsInternet protocol that uses distance vectors –The “Tell your neighbor everything” protocol Link state protocolsLink state protocols –Developed in late 1970s on the ARPANET –OSPF protocol – Open Shortest Path First Internet protocol that uses link stateInternet protocol that uses link state –The “Tell everyone about your neighbors” protocol

15. 10/1/2015 15R. Smith - University of St Thomas - Minnesota Distance Vector Protocols What it doesWhat it does –Figures out how far “this node” is from everyone else. Save in a huge tableSave in a huge table Share the table with your neighborsShare the table with your neighbors How it worksHow it works –Keep a list of all hosts in the network. For each host: Which interface gives the shortest path to that hostWhich interface gives the shortest path to that host Delay (number of hops) to reach that hostDelay (number of hops) to reach that host –Exchange the (big) list of delays with your neighbor

16. Updating your routes The stepsThe steps –Get the list from your neighbor –For each non-neighbor, add a hop (delay) to get to them –If that count is less than what’s already in your table, Update your table with the new delayUpdate your table with the new delay The link to that neighbor yields the best path to that host.The link to that neighbor yields the best path to that host. The node doesn’t care WHO its neighbors are!The node doesn’t care WHO its neighbors are! “Tell your neighbor everything”“Tell your neighbor everything” –Big messages sent to neighbors only 10/1/2015 16R. Smith - University of St Thomas - Minnesota

17. Let’s do an example Six nodesSix nodes Two west, two middle, two eastTwo west, two middle, two east Parallel connections north-south on all 3 pairParallel connections north-south on all 3 pair Parallel connections acrossParallel connections across –Three westward –Two eastward 10/1/2015 17R. Smith - University of St Thomas - Minnesota

18. ARPANET Distance Vector Protocol Address: 6 bits of ‘node’ and 2 bits of ‘host’Address: 6 bits of ‘node’ and 2 bits of ‘host’ –1 entry per node –So, how big was the distance vector table? New Address: 24 bits: 16 bits node, 8 bits hostNew Address: 24 bits: 16 bits node, 8 bits host –So, how big was a distance vector table? –Was this practical? 10/1/2015 18R. Smith - University of St Thomas - Minnesota

19. 10/1/2015 19R. Smith - University of St Thomas - Minnesota Link State Protocols What it doesWhat it does –Tell everyone who your neighbors are –Use those messages to incrementally build a network map How it worksHow it works –Measure the delay to reach your neighbors –Broadcast a list of your neighbors to everyone on the network These are “link state” messagesThese are “link state” messages

20. Updating your routes The StepsThe Steps –As they arrive, use the link state messages to build a tree- shaped map of the network, indicating the shortest path from you to the other hosts on the network –If a new message uncovers a shorter path, fix your tree –To route a message, find the host and see which interface yields the shortest path, as shown by your tree “Tell everyone about your neighbors”“Tell everyone about your neighbors” –Small messages sent to everyone The node CARES about who the neighbors areThe node CARES about who the neighbors are 10/1/2015 20R. Smith - University of St Thomas - Minnesota

21. A final example Six nodesSix nodes Two west, two middle, two eastTwo west, two middle, two east Parallel connections north-south on all 3 pairParallel connections north-south on all 3 pair Parallel connections acrossParallel connections across –Three westward –Two eastward 10/1/2015 21R. Smith - University of St Thomas - Minnesota

22. 10/1/2015 22R. Smith - University of St Thomas - Minnesota Quality of Service Elastic vs Inelastic servicesElastic vs Inelastic services –A familiar concept, different terms –Possibly elastic/inelastic properties ThroughputThroughput DelayDelay Delay variationDelay variation Packet lossPacket loss Differentiated Services (DS)Differentiated Services (DS) –Uses a field in IP packet to identify different handling needs –Can simply be “priority” Send it ahead of lower priority trafficSend it ahead of lower priority traffic Discard other packets before this one if space is tightDiscard other packets before this one if space is tight –Routers can provide “guaranteed service” for selected DS settings (at UST, CLIC service has a small guaranteed bandwidth)

23. 10/1/2015 23R. Smith - University of St Thomas - Minnesota Creative Commons License This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by- sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.