Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706
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Data Communications and Networks I • 4003-420-01/4005-740-01 • Fall Quarter 2012
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4003-420-01/4005-740-01 Data Communications and Networks I
Module 4. Network Layer -- Lecture Notes

Prof. Alan Kaminsky -- Fall Quarter 2012
Rochester Institute of Technology -- Department of Computer Science

Key Organizing Principle For This Course

  • What do I need to know about topic X to write network applications?

  • What issues related to topic X affect network application design?

Packet Routing

  • Routers (packet switches)
    • Connections to end computers (hosts)
    • Connections to other routers
    • Incoming lines
    • Outgoing lines
    • Outgoing packet buffers (queues)

  • Router operation -- store and forward
    • What happens when an outgoing packet buffer is full
    • Congestion issues

  • Hierarchical packet addressing
    • Network number
    • Host number within the network

  • Forwarding table
    • Network number --> next hop (outgoing line)

  • Filling in the forwarding table -- routing algorithm
    • Shortest path routing
    • Shortest path based on hop count
    • Shortest path based on link weight

IP Addresses

  • IP: The Internet Protocol (Version 4, IPv4)

  • IP address
    • 32-bit number
    • Dotted decimal notation

  • Parts of an IP address (network number, host number)
    • Original scheme: Classes A, B, C, D, E
    • Present scheme: Classless Inter-Domain Routing (CIDR)
      • CIDR notation
      • Subnet mask notation

  • The Domain Name System (DNS)
    • Translates host names (www.cs.rit.edu) to IP addresses (129.21.30.99, or 10000001000101010001111001100011)

IP Datagrams

  • Unreliable datagram delivery service
    • Causes of packet loss

  • IP datagram format -- RFC 791

  • IP datagram forwarding
    • IP router forwarding table

  • IP datagram encapsulation
    • Payload inside a frame of the underlying Data Link Layer

  • IP datagram fragmentation
    • Maximum Transmission Unit (MTU) of the underlying Data Link Layer
    • Fragmentation process -- at any router along the path
    • Reassembly process -- in the destination host
    • Effect of fragmentation on the probability of successful datagram delivery

Network Layer Issues Affecting Network Application Design

  • Unreliable datagram delivery issues

  • Congestion issues

  • Datagram fragmentation issues

Data Communications and Networks I • 4003-420-01/4005-740-01 • Fall Quarter 2012
Course Page
Alan Kaminsky • Department of Computer Science • Rochester Institute of Technology • 4486 + 2220 = 6706
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Copyright © 2009 Alan Kaminsky. All rights reserved. Last updated 24-Sep-2009. Please send comments to ark­@­cs.rit.edu.