Advanced topics in Computer Networks

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Advanced topics inComputer Networks
Lecture 1 Introduction

• University of Tehran
• Dept. of EE and Computer Engineering
• By
• Dr. Nasser Yazdani

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Outline

• Agenda
• Policy, Grading, reading materials, etc.
• Overview of course materials
• Computer Network trend

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Agenda

• To establish a base for future computer networks
  research and development.
• To discuss latest developments in computer
  networking and telecommunications via class
  lectures and assigned readings.
• To find the current research issues in the field.
• Finally, prepare to perform some projects in
  computer networks which are essential in national
  development, designing and building switches,
  routers, etc.

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Course Materials

• Course Web page
• visit regularly
• Research papers
• Printed papers or pdf/ps format on the Website
• Combination of classic and recent work.
• Class notes of Dr. Turner on switching.
• Textbooks
• For Class reading
• ATM switching systems by Thomas M. Chen and ..
• MPLS technology and Applications by Bruce Davie
  and ..
• Background reading, so many books including
• Computer Networks, A system approach. Peterson
  Davie 2nd edition

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Grading

• Homework assignments, around 20
• Presentations
• One paper presentation, around 1 hour.
• Final project presentation, around 20 minutes.
• One hands-on assignment.
• Severe late penalties!
• Project around 45
• Exam, final around 40.

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Policy

• The course is research oriented. Then, the main
  focus will be project and paper reading.
• We will focus more packet switch, but open to new
  areas like mobile and wireless networks, QoS,
  etc.
• There will be a lot of reading and work. Then, be
  prepared!.

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Covered topics

• The focus point of the course will be packet
  switching covering the following topics
• ATM networks
• Switching architecture.
• Lan switching, bridges, IP over ATM.
• IP lookup
• Packet classification
• Label Switching.
• Tag switching, IP switching.
• Multiprotocol Label switching (MPLS
• Network processors (?)

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Asynchronous Transfer Mode Networks (ATM)

• ATM networks introduced commercially in early
  nineties.
• designed to match packet networks ability to
  serve many different applications
• improve support for real-time applications by
  allowing bandwidth reservation and support for
  guaranteed Quality of Service (QOS)
• improve support for multicast applications with
  built-in signaling mechanisms
• improve performance through high performance,
  scalable hardware switching
• improve scaling using general hierarchical
  addressing and two multiplexing levels

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ATM (Cont)

• Overall characteristics
• cell-based switching with virtual circuit and
  virtual path routing
• short, fixed-length cell to facilitate hardware
  switching reduce delay variability
• hardware support for unicast and multicast
  forwarding
• general signaling protocol for establishment of
  unicast and multicast sessions
• comprehensive traffic management framework
  supporting bandwidth reservation and QOS
  emphasis on high quality services.

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ATM (Cont)

• Competition between IP ATM has improved both.
• efforts to add QoS and multicast signaling
  capabilities to IP
• introduction of hardware switching techniques
  in IP routers
• improved congestion control mechanisms for data
  in ATM
• extending ATM multicast to support many-to-many

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Switching

• Switching systems
• use cell labels to forward cells to destination
• accommodate differences in terminal devices
• allow large networks to be built economically
• Cell switches must be programmed to forward
  cells.

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Switching (Cont)

• Input and Output Transmission
• Interfaces (ITI, OTI)
• convert between serial
• optical signals and parallel
• electrical signals
• extract timing from received signals
• encode (and decode) data
• for transmission
• Input Port Processors (IPP)
• synchronize received signals
• determine required output or outputs using
  routing table
• Output Port Processors (OPP)
• queue outgoing cells
• Shared bus interconnects IPPs and OPPs.
• Control Processor (CP)
• configures routing tables to implement
  end-to-end channels
• accepts requests for channels from terminals
• coordinates end-to-end channel setup together
  with CPs in neighboring switches

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Layer 2 switching

• Interlan switches, bridge are powerful but not
  scalable to WAN.
• Problem with Layer 2 switching is that it takes
  network as a flat network.
• Virtual LANS is used to overcome location
  limitation for LAN.
• VLAN is a broadcast domain, emulates the idea of
  being in the same physical LAN.
• More Flexible, Secure, Efficient compare to LANS
• By appending a Tag to the packet which identifies
  the VLAN.

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WAN Switching

• There are two major problems in scaling LAN
  switching to WAN.
• Broadcast storm on the net.
• The size of lookup table.
• Switch needs a way to identify output port
  without broadcasting at startup.
• Use existing switching technology to send IP (
  IP over ATM)
• Identify each flow with an ID.

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IP Lookup

• Packets are forwarded to their destination based
  on their destination addresses.
• Router must find the address of the next hop for
  each packet by finding the longest prefix
  matching with the packet destination address.

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IP lookup (Cont)

• Example

If the a packet destination address is
101100111, the next hop will be 3 since 1011001
is the longest matching prefix.
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Packet Classification

• Security and Filtering. Block unauthorized
  access. It is important on the access point of a
  network.
• Differentiated Services.
• Policy based routing.
• Billing.
• Isolating traffic from different users
• Quality of Service.
• Special queuing and scheduling.
• Traffic shaping.

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General View
Routing
Reservation, Signaling Management
Classifier
State
IP input Processing
IP output Processing
Filter
Action




IP Packet
IP Packet
Scheduler
Input driver
Output driver
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General framework

• Each filter or rule consist of two sections,
  packet header information and actions or rule

Packet headers Packet headers Packet headers Packet headers Rule or Action
Header 1 Header 2 . Header K

• Header information uniquely identify packet of a
  flow.
• Rule can be for security, forwarding or QoS of
  service rule.
• Questions?
• Which combination of header fields?
• How to formulize and map QoS, InterServ,
  DiffServ, etc.
• parameters to these rule?
• How MPLS can be coupled with this classification
  scheme?

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TAG Switching

• The idea is to identify a flow with an ID.
• It combines label swapping with network layer
  routing.
• It is the base of MPLS, Multiprotocol Label
  Switching, protocol.
• It was originally proposed by CISCO.
• The Components
• Forwarding
• Control. Maintaining correct tags.

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TAG Switching (Cont)

• Forwarding is based on Label swapping.
• Each packet carry a tag, id with itself.
• There is a Tag Forwarding Information Base(TFIB)
  table in the switch.

Incoming Tag Outgoing Tag Outgoing interface Outgoing link level inform.
If the switch finds a entry with the incoming
tag, it replaces the tag in the packet with the
outgoing tag and the link information, and
forwards it to the outgoing interface.
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MPLS (Multiprotocol label switching)

• To utilize ATM switching technique in IP routers.
  This improve the price/performance of forwarding
  process.
• To simplify forwarding and routing process. Use
  MPLS tags for forwarding instead of IP header.
  This improve scalability of network layer
  forwarding.
• To extend the functionality and flexibility in
  bringing new services such as traffic shape, QoS,
  etc in an easy and manageable manner.
• And more ..

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Quality of Service

• Related topics
• Signaling and admission control.
• Traffic shaping
• Scheduling
• Buffer management
• Constrained based routing
• Quality of Service protocols for IP
• Integrated services
• RSVP

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Network processor

• We can identified two almost independent parts in
  the design.

We are using two chips to implement the whole
functionalities. We call each chip network
processor for the sake of simplicity.
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Network processor (Cont)

• The first Network Processor (NP0) does
• Parsing
• Writing ingress packets in the SRAM
• Filtering
• Classification
• Reading and Dispatching egress packets to the
  Physical line.
• Sending packet headers to ALU for routing and NP1
  for scheduling.

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Network processor (Cont)

• The Second Network Processor (NP1) does
• Scheduling
• Queuing
• Reading ingress packets from the SRAM
• Dispatching ingress packets to the switch.
• Receiving egress packet from switching and
  writing them into the RAM.
• Signaling for port and physical address finding.

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Outline

• Agenda
• Policy, Grading, reading materials, etc.
• Overview of course materials
• Computer Networking trends

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Trends

• Technology trends.
• Driving forces.
• Fast Immediacy
• Impact on RD
• Impact on Education
• Convergence
• Information Glut
• Networking Trends

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Driving forces

• Exponential growth.

Number of Hosts on the Internet Aug. 1981
213 Oct. 1984 1,024 Dec. 1987
28,174 Oct. 1990 313,000 Oct. 1993
2,056,000 Apr. 1995 5,706,000 Jul. 1997
19,540,000 Jul. 1999 59,249,900 Jul. 2001
117,288,000