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


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.
2

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
3

Introduction and History (Cont’d)
Circuit Switching
4

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
5

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
6

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

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
8

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
9

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

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
11

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
12

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

Switches and Routers

What is a switch and what is a router?

The problem with achieving performance

The need for buffers
Packet headed to output 0
Packet headed to output 1
(a)
0
1
0
1
0
1
0
1
Before After
(b)
0
1
0
1
0
1
0
1
Before After
14

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

Switches and Routers (Cont’d)
0
1
Head-of-line blocking with input queueing
Packet headed to output 0
Packet headed to output 1
0
1 1
0
0
1
End of Cycle 2
End of Cycle 1
16

Switches and Routers (Cont’d)
0
1
Output queueing and head-of-line blocking
Packet headed to output 0
Packet headed to output 1
0
1
0
1
0
1
End of Cycle 2
End of Cycle 1
17

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
18

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
19

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
20

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

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
22

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
23

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
24

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

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
26

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

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

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
29

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

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
31

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
32

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
33

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?
34

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.
35

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
36

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
37

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
38

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
39

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

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
41

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
42

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
43

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
44

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

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
46

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

Multi-Protocol Label Switching
(Cont’d)
A limitation of traditional routing:
Point of
Congestion
1
A
4
A & B
A & B
3 6
B
2 5
48

Multi-Protocol Label Switching
(Cont’d)
MPLS extends routing functionality:
1 4
A
A A
3 6
B
B B
2 5
49

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.
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