Download ECE537-Class 1_2009 - Worcester Polytechnic Institute

ECE537 Advanced and High
Performance Networks
1: Network Layer Review
Professor Richard A. Stanley, P.E.
Spring 2009
© 2000-2009, Richard A. Stanley
ECE506/2 #1
Overview of Tonight’s Class
• Administration
• Is computer security a problem, or just an
interesting topic?
• What is different between computer security
and network security?
• Computer security objectives and
approaches
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Organizational Details
• Prof. Stanley contact information
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Office:
Hours:
Phone:
Email:
Atwater-Kent 303, but rarely there
by appointment, preferably after class
(508) 269-6482
[email protected]
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Administrivia
• Class will normally meet 4:00 – 8:00 PM
every Wednesday here. Please be on time.
• We will hold 10 classes; cancellations will
be announced in advance (except weather)
• Breaks as needed
• If class is cancelled for bad weather, you
should receive notice. Double-check with
ECE Dept. (5231) or with me if in doubt.
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Recall
• We need to set up a way for notification of
cancelled/late classes
• Please put the following information on the
sheet going around:
– Name
– Email
– Telephone
• Volunteer to be at the top of the list?
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Course Text
• None.
• Additional material will be in the form of
handouts and research reports
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Course Web Page
• http://ece.wpi.edu//courses/ee579sw/ECE537
• Slides will be posted to the page before
class, barring any unfortunate problems
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Policies
• Homework is due at the class following the one in
which it is assigned. It will be accepted--with a
one grade penalty--up to the second class after that
in which it is assigned, but not after that, except in
truly emergency situations. By definition,
emergencies do not occur regularly.
• There is a difference between working in teams
and submitting the same work. If work is a team
product, it must be clearly labeled as such.
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Elements of the Course
• Assignments: There will be weekly assignments,
which will be graded
• Presentation: At the end of the course, student
teams will present a report prepared on a
cryptography-related subject. The presentation
should be well-prepared and should give an overview
of a special topic in cryptography (e.g. eCash,
wireless security, SSL, biometric authentication
systems etc.).
• Examinations: There will be a two written
examinations that will cover all topics discussed in
class. The questions will range from mild to hard.
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Research Projects
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Teams of 3-5 individuals per project
Research an advanced networking topic
Prepare a report on the research
Present findings
– Note: a presentation is not the report copied
into PowerPoint
• Given the nature of this course, we will do
mini-reports throughout
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Grading
• Grade components
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Course exams (30%)
Homework (10%)
Class participation (10%)
Course projects (50%)
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Course Topics
• Ad hoc networking
• Network extensions by wireless means
• Management challenges in high
performance networks
• Colored and colorless networks
• Emerging network technologies
• Your preferences?
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Link Layer: Ethernet
Spring 2009
© 2000-2009, Richard A. Stanley
ECE506/4 #13
Internet Architecture
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Fundamental Network Layer
Function
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Data Flow Across Layers
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Protocol Layering and Data
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Network Service Model
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Virtual Circuits
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Packet Switching
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Packet Switching vs. Virtual Circuits
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Routing Principles
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Interplay between routing and forwarding
routing algorithm
local forwarding table
header value output link
0100
0101
0111
1001
3
2
2
1
value in arriving
packet’s header
0111
1
3 2
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Datagram or VC network: why?
Internet
ATM
• data exchange among computers • evolved from telephony
– “elastic” service, no strict
• human conversation:
timing req.
– strict timing, reliability
• “smart” end systems (computers)
requirements
– can adapt, perform control,
– need for guaranteed service
error recovery
• “dumb” end systems
– simple inside network,
– telephones
complexity at “edge”
– complexity inside network
• many link types
– different characteristics
– uniform service difficult
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Router Architecture Overview
Two key router functions:
• run routing algorithms/protocol (RIP, OSPF, BGP)
• forwarding datagrams from incoming to outgoing
link
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Input Port Functions
Physical layer:
bit-level reception
Data link layer:
e.g., Ethernet
see chapter 5
Decentralized switching:
• given datagram dest., lookup output
port using forwarding table in input port
memory
• goal: complete input port processing at
‘line speed’
• queuing: if datagrams arrive faster than
forwarding rate into switch fabric
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Three types of switching fabrics
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Switching Via Memory
First generation routers:
• traditional computers with switching under direct control of
CPU
•packet copied to system’s memory
• speed limited by memory bandwidth (2 bus crossings per
datagram)
Input
Port
Memory
Output
Port
System Bus
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Switching Via a Bus
• datagram from input port memory
to output port memory via a shared
bus
• bus contention: switching speed
limited by bus bandwidth
• 1 Gbps bus, Cisco 1900: sufficient
speed for access and enterprise
routers (not regional or backbone)
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Switching Via An Interconnection
Network
• Overcome bus bandwidth limitations
• Banyan networks, other interconnection nets
initially developed to connect processors in
multiprocessor
• Advanced design: fragmenting datagram into
fixed length cells, switch cells through the fabric.
• Cisco 12000: switches Gbps through the
interconnection network
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Output Ports
• Buffering required when datagrams arrive from
fabric faster than the transmission rate
• Scheduling discipline chooses among queued
datagrams for transmission
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Output port queueing
• buffering when arrival rate via switch exceeds
output line speed
• queueing (delay) and loss due to output port buffer
overflow!
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Input Port Queuing
• Fabric slower than input ports combined -> queueing
may occur at input queues
• Head-of-the-Line (HOL) blocking: queued datagram
at front of queue prevents others in queue from
moving forward
• queueing delay and loss due to input buffer
overflow!
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Routing Algorithms
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A Link-State Routing Algorithm
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Dijkstra’s Algorithm
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Dijkstra’s Algorithm Example
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Dijkstra’s Algorithm Discussion
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Network Routing
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Distance Vector Routing
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Constructing Distance Vector
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DV Algorithm Example
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DV Algorithm Example
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Maintaining the Distance Vector
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Link Cost Changes
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Link Cost Changes (con’t.)
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DV Poisoned Reverse
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Routing Loops
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Distance Vector Example
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Distance Vector to Routing Table
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LS & DV Algorithms Compared
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Internet Network Layer
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IP Addressing
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IP Network & Hierarchical
Addressing
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IP Addressing: Original Standard
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IP Addressing: CIDR
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DHCP
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NAT
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IP Packet Format (v4)
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Packet Fragmentation & Reassembly
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Routing on the Internet
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Hierarchical Routing
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Intra-/Inter-AS Routing
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Intra-AS & Inter-AS Routing
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Internet Routing
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RIP: An Intra-AS Routing Protocol
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RIP Example
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RIP Example (2)
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RIP Table Processing
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RIP Table Example
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OSPF: Another Intra-AS Routing
Protocol
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Hierarchical OSPF
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Inter-AS Routing in the Internet
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BGP Routing Protocol
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BGP: Controlling Who Routes to
You
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BGP: Controlling Who Routes to
You
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BGP Routing Table: Whole Internet
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Why Two-Level Intra- and Inter-AS
Routing?
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Summary
• Network layer takes care of routing
datagrams
• Routing protocols either link status or
autonomous system based
• IP a very common network layer protocol,
but far from the only one!
• Routing protocols are complex and can be a
topic of long study all by themselves
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Homework
• Research IPv6 and prepare a paper or
presentation on this protocol (1100 words or
so as a guideline). What does it bring that
IPv4 does not provide? What does it lack?
What is the good, the bad, and the ugly of
this protocol?
Spring 2009
© 2000-2009, Richard A. Stanley
ECE506/4 #80
Disclaimer
Parts of the lecture slides contain original
work of James Kurose, Larry Peterson,
Keith Ross, Eytan Modiano, Liudvikas
Bukys, and Henry Warren, and remain
copyrighted materials by the original
owner(s). The slides are intended for the
sole purpose of instruction of computer
networks at Worcester Polytechnic Institute.
Spring 2009
© 2000-2009, Richard A. Stanley
ECE506/4 #81