1 Emerging Internet Technologies Harish Sethu Department of Electrical and Computer Engineering Drexel University

2 Introduction and History  More rapid growth than any medium in history  New applications in education, business and medicine  Impact on entertainment, politics and the day-to-day lives of people  Internet still very young, and rapidly evolving.

3 Introduction and History (Cont’d) The Origin  Began as ARPANET in 1969 for the purpose of sharing computing resources  ARPANET was funded by the Department of Defense  Met with resistance even by university research groups who did not wish to be linked to the ARPANET  Used packet switching as opposed to circuit switching

4 Introduction and History (Cont’d) Circuit Switching

5 Introduction and History (Cont’d) Circuit Switching  Physical connection established between communicating end-points.  Requires setting up the connection before communication  Guaranteed bandwidth  Predictable and bounded delay

6 Introduction and History (Cont’d) Packet Switching  No physical connection established between communicating end-points.  Data is sent in blocks called packets  Each packet is routed independently

7 Introduction and History (Cont’d) Packet Switching Packet 1 Packet 2

8 Introduction and History (Cont’d) Packet Switching vs. Circuit Switching  Packets may arrive out-of-order  Packets may be dropped, since network does not guarantee bandwidth  Packet switching analogous to how we share road space

9 Introduction and History (Cont’d) The origins of packet switching  The roles of Leonard Kleinrock, Paul Baran and Donald Davies  BBN’s proposal to use packet switching for ARPANET  The travails of packet switching

10 Introduction and History (Cont’d) Milestones  Ethernet  TCP/IP   Commercialization of the Internet  World Wide Web

11 Introduction and History (Cont’d) Internet Organizations  The Internet Society  The Internet Architecture Board  The Internet Engineering Task Force  The Internet Engineering Steering Group  ICANN

12 Protocol Layering  What is a protocol?  What is protocol layering?  The analogy to postal service.  Why use protocol layering?  Simplicity in design  Flexibility in accommodating new technologies  Compatibility of applications to systems

13 Protocol Layering (Cont’d) A common implementation Application Layer Transport Layer Network Layer Access Layer Physical Layer Application Layer Transport Layer Network Layer Access Layer Physical Layer Application protocol, e.g., HTTP Transport protocol, e.g., TCP Network protocol, e.g., IP Network access protocol, e.g., Ethernet Physical medium, e.g. copper System 1 System 2 Application Layer Transport Layer Network Layer Access Layer Physical Layer Application Layer Transport Layer Network Layer Access Layer Physical Layer

14 Switches and Routers  What is a switch and what is a router?  The problem with achieving performance  The need for buffers Before After Packet headed to output 0 Packet headed to output Before After (a) (b)

15 Switches and Routers (Cont’d) Input queueing and output queueing

16 Switches and Routers (Cont’d) Head-of-line blocking with input queueing Packet headed to output 0 Packet headed to output End of Cycle End of Cycle

17 Switches and Routers (Cont’d) Output queueing and head-of-line blocking 0 1 End of Cycle End of Cycle Packet headed to output 0 Packet headed to output 1

18 Switches and Routers (Cont’d) Commercial switches and routers  Use both input and output queueing  Use shared buffer for output queueing  Use complex buffer organizations and queue management strategies

19 Virtual Circuit Switching  Establishes a virtual circuit  Routes using a virtual circuit identifier on each packet  Packets with same identifier routed identically by a switch  Facilitates easy management of flows of traffic

20 Virtual Circuit Switching (Cont’d) Asynchronous Transfer Mode (ATM)  Uses virtual circuits  Proposed for providing performance guarantees as in circuit switching using the packet switching technology  Largely used today in the Internet backbone

21Routing  What is routing?  What is a route table?  What is a “best” route?

22 Routing (Cont’d) Link State Routing Link State Routing  Periodically measure cost to each neighbor  Distribute measurements to all routers in the network  Each router has complete and current information on the topology  Each router independently computes the “best” path

23 Routing (Cont’d) Distance-Vector Routing  Each router maintains a distance-vector, the cost to reach each destination from itself.  Exchanges distance-vectors with neighbors  Determines the “best” path neighbor to reach destination

24 Routing (Cont’d) Routing in the Internet  Distance-vector routing used in the Internet core (BGP)  Link-state routing used within domains (OSPF)  Border routers use both

25 Flow Control and Congestion Avoidance  What is flow control?  What is congestion avoidance?  Design goals:  responsiveness  performance  scalability  simplicity  fairness

26 Flow Control and Congestion Avoidance (Cont’d) Flow control strategies  Open loop flow control  No feedback  Pre-arranged self-regulation at the source  Closed loop flow control  Self-regulation based on feedback

27 Flow Control and Congestion Avoidance (Cont’d) Open loop flow control  Traffic descriptors  Token bucket regulator  token generation  bucket capacity

28 Flow Control and Congestion Avoidance (Cont’d) Token bucket regulator Before Network After Packets Tokens Token Bucket

29 Flow Control and Congestion Avoidance (Cont’d) Closed loop flow control Closed loop flow control  TCP uses closed loop flow control  slow-start phase in TCP (exponential rate increase)  congestion-avoidance phase in TCP (linear rate increase)  time-outs and back-off

30 Flow Control and Congestion Avoidance (Cont’d) A typical saw-tooth graph of TCP sending rate Time Threshold Time-out occurs due to congestion Exponential increase Linear Increase TCP Send ing rate New threshold

31 Flow Control and Congestion Avoidance (Cont’d) Problems with TCP Problems with TCP  Does not avoid congestion, reacts only after congestion  Assumes time-outs are always due to congestion  Always keeps pushing the network into congestion

32 Flow Control and Congestion Avoidance (Cont’d) Random Early Detection (RED)  Defines router actions designed to work with TCP  Goal is congestion avoidance, at good performance  Detects impending congestion based on queue length  Drops packets before congestion occurs  Triggers TCP to cut down its rate before it causes congestion  Used in most Internet routers today

33 Emerging Architectures and Services  Onslaught of multimedia traffic  Need for service beyond best effort  What is Quality of Service?  throughput guarantee  delay bound  delay-jitter bound

34 Fairness in Traffic Management  The most basic guarantee: fairness.  Why not just first-come-first-serve?  Why not just packet-by-packet round-robin scheduling?

35 Fairness in Traffic Management (Cont’d) What is fair and how to be fair? What is fair and how to be fair?  All flows with unsatisfied demands should get an equal share of the resource  No flow should be allocated more resources than its demand  Fair queueing is a technique that achieves the above two conditions for fairness to a satisfactory extent.  Most Internet routers now implement some version of a fair queueing discipline.

36 The Integrated Services Model  A new architectural framework to facilitate QoS in the Internet.  Applications describe their traffic to the network, and their demand for QoS  Network decides if the demand can be satisfied before admitting the application traffic  Routers reserve bandwidths and buffers necessary to satisfy demand

37 The Integrated Services Model (Cont’d) Flow specifications TSpec  burst size  long-term average rate  maximum packet size  peak rate RSpec  service rate  delay bound  packet loss probability

38 The Integrated Services Model (Cont’d) Service Classes Guaranteed service Guaranteed service  Provides hard guarantees  Requires per-flow management in the routers  Suffers from scalability problems Controlled Load Service Controlled Load Service  Service similar to best-effort in a lightly loaded network  Meant for applications that can tolerate some loss or delay  Requires application to specify traffic description  Network decides whether or not to admit a new flow for controlled load service

39 The Integrated Services Model (Cont’d) Signaling (RSVP)  RSVP is an IP signaling protocol  Uses two messages: Path and Resv  Path messages go from the sender to the receiver, containing traffic description  Resv messages go from receiver to the sender, containing QoS requirements

40 The Integrated Services Model (Cont’d) Flow of Path and Resv messages Sender Receiver 1 Receiver 3 Path Resv

41 The Integrated Services Model (Cont’d) Multicasting with RSVP  RSVP explicitly designed for multicast  Multicast method based on data replication in the network  Allows merging of Resv requests  RSVP is a soft-state protocol

42 The Differentiated Services Model  Differentiated Serevices model is more scalable.  Traffic is divided into classes  Resources allocated on a per-class basis instead of a per-flow basis  Defines a set of Per-Hop Behaviors (PHBs)  Service by the network based on the PHB carried in the packet  Standard PHBs  Expedited Forwarding  Assured Forwarding

43 The Differentiated Services Model (Cont’d) Expedited Forwarding (EF-PHB)  A request to forward the packet as quickly as possible  Meant for applications with stringent delay requirements  Requires strict regulation at source  Requires careful capacity planning

44 The Differentiated Services Model (Cont’d) Assured Forwarding (AF-PHB) Assured Forwarding (AF-PHB)  Delivers with high assurance (a weaker guarantee)  Consists of 4 classes and 3 drop precedence levels  In-order delivery within each class  Drop precedence defined at the source end

45 The Differentiated Services Model (Cont’d) A potential DiffServ scenario Internet backbone network Hosts Drexel University DS Domain Border router Hosts Service Level Agreement made on aggregated rate ISP router

46 Multi-Protocol Label Switching  Uses the concept similar to that of virtual circuits in IP  Uses fixed-size labels  Originally designed to facilitate sending IP packets over ATM  Packets are routed based on the label, instead of destination address.  Supported by high-end routers today  Achieves lower header overhead

47 Multi-Protocol Label Switching (Cont’d) Achieves separation of control and forwarding components: Routing Protocols Routing Tables Updates to/from other routers Updates to/from other routers Forwarding Tables Forwarding Fabric Packets with labels Packets with labels Control Component Forwarding Component

48 Multi-Protocol Label Switching (Cont’d) A limitation of traditional routing: B A A & B Point of Congestion

49 Multi-Protocol Label Switching (Cont’d) MPLS extends routing functionality: B A A A B B

50 Concluding Remarks  Internet is still evolving, and very rapidly.  Service requirements of applications may change; new solutions such as active networking are emerging.  Engineering the Internet continues to be both challenging and rewarding.