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Emerging Internet Technologies: 

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

Introduction and History: 

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.

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

Introduction and History (Cont’d) Circuit Switching

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

Introduction and History (Cont’d) Packet Switching

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

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

Introduction and History (Cont’d): 

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

Protocol Layering: 

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

Protocol Layering (Cont’d): 

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

Switches and Routers: 

Switches and Routers What is a switch and what is a router? The problem with achieving performance The need for buffers

Switches and Routers (Cont’d): 

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

Switches and Routers (Cont’d): 

Switches and Routers (Cont’d) Head-of-line blocking with input queueing

Switches and Routers (Cont’d): 

Switches and Routers (Cont’d) Output queueing and head-of-line blocking

Switches and Routers (Cont’d): 

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

Virtual Circuit Switching: 

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

Virtual Circuit Switching (Cont’d): 

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

Routing: 

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

Routing (Cont’d): 

Routing (Cont’d) 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

Routing (Cont’d): 

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

Routing (Cont’d): 

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

Flow Control and Congestion Avoidance: 

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

Flow Control and Congestion Avoidance (Cont’d): 

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

Flow Control and Congestion Avoidance (Cont’d): 

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

Flow Control and Congestion Avoidance (Cont’d): 

Flow Control and Congestion Avoidance (Cont’d) Token bucket regulator

Flow Control and Congestion Avoidance (Cont’d): 

Flow Control and Congestion Avoidance (Cont’d) 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

Flow Control and Congestion Avoidance (Cont’d): 

Flow Control and Congestion Avoidance (Cont’d) A typical saw-tooth graph of TCP sending rate

Flow Control and Congestion Avoidance (Cont’d): 

Flow Control and Congestion Avoidance (Cont’d) 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

Flow Control and Congestion Avoidance (Cont’d): 

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

Emerging Architectures and Services: 

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

Fairness in Traffic Management: 

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?

Fairness in Traffic Management (Cont’d): 

Fairness in Traffic Management (Cont’d) 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.

The Integrated Services Model: 

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

The Integrated Services Model (Cont’d): 

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

The Integrated Services Model (Cont’d): 

The Integrated Services Model (Cont’d) Service Classes Guaranteed service Provides hard guarantees Requires per-flow management in the routers Suffers from scalability problems 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

The Integrated Services Model (Cont’d): 

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

The Integrated Services Model (Cont’d): 

The Integrated Services Model (Cont’d) Flow of Path and Resv messages

The Integrated Services Model (Cont’d): 

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

The Differentiated Services Model: 

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

The Differentiated Services Model (Cont’d): 

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

The Differentiated Services Model (Cont’d): 

The Differentiated Services Model (Cont’d) 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

The Differentiated Services Model (Cont’d): 

The Differentiated Services Model (Cont’d) A potential DiffServ scenario

Multi-Protocol Label Switching: 

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

Multi-Protocol Label Switching (Cont’d): 

Multi-Protocol Label Switching (Cont’d) Achieves separation of control and forwarding components:

Multi-Protocol Label Switching (Cont’d): 

Multi-Protocol Label Switching (Cont’d) A limitation of traditional routing:

Multi-Protocol Label Switching (Cont’d): 

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

Concluding Remarks: 

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.