The Network Layer

1
The Network Layer

• Forwarding
• Internal path to follow
• Routing
• External path to follow
• Models
• Guaranteed delivery with or without bounded delay
• In-order packet delivery
• Guaranteed minimal bandwidth
• Guaranteed maximum jitter

2
test
3
Virtual Circuits

• Connection Oriented
• Connection state information
• Phases
• VC Setup
• Data Transfer
• VC Teardown

4
Datagram Networks

• Internet
• Not connection oriented
• No guarantee of delivery
• Faster

5
Routing

• Address 129.123.3.0 Interface 0
• Address 129.123.7.0 Interface 1
• Address 129.123.7.40 Interface 2
• Address 129.123.63.0 Interface 3
• Address 129.123.73.0 Interface 4

6
Routers
7
Router Switching
8
Queueing

• Packet Scheduling
• Quality of Service
• Active Queue Management

9
Router Configuration

• http//www.cs.usu.edu/bobw/cs4720/CISCO.txt
• Lookup
• Helper addresses
• Forwarding
• Queueing
• Other protocols
• IPX/SPX (Novell, Microsoft)
• Appletalk (Macintosh)
• DECnet (card readers)

10
Routing on the Internet

• RIP (Routing Internet Protocol)
• Lots of traffic (advertisements)
• Not very efficient
• Basically obsolete
• OSPF (Open Shortest Path First)
• Flooding
• Secure
• Multiple same cost paths
• Multicast and Unicast capable

11
Router Monitoring

• Traceroute (tracert)
• Simple routing test
• USUs Web site for monitoring
• http//pomoxis.usu.edu/network/grapher.cgi?target
  2Fnetwork-devices2Frouter-interfaces
• Whats UP
• http//floyd.usu.edu

12
IP Network Communication

• IPv4 Addressing
• Network Layer (IP, Layer 3)
• Protocols are described in RFCs (Request for
  Comments)
• Available from nis.nsf.net/internet/documents/rfc
• TCP/IP Addressing
• Class A (1-126).xxx.xxx.xxx
• Class B (128-191).(assigned).xxx.xxx
• Class C (192-223).(assigned).(assigned).xxx

13
Internet Addressing

• Each address is 4, 8 bit, decimal numbers
• Like Area Code/Exchange/Subscriber
• 129.123.7.170
• 129.123 is assigned to USU (domain)
• 172.xxx.xxx.xxx USU nonroutable
• 7 is assigned to Computer Science
• 170 is assigned to PC named java4
• Every Internet device must have a number
• Number to name conversion is done by DNS

14
IP header

• Version number (4 bits)
• Tells router how to interpret datagram
• Type of Service
• Selects delivery speeds vs. accuracy
• Datagram Length (16 bits) rarely longer than 1500
  bytes
• Identification, Flags and Fragment offset
• Reassembly of a fragmented datagram
• Time to Live
• Router hops, control routing loops
• Protocol (TCP,ICMP, UDP)
• Header Checksum
• Source and Destination IP addresses

15
IP Header
Version
Leng
Type of Svc
Total Length
Identification
Flags
Frag Offset
Time to Live
Protocol
Header Checksum
Source Address
Destination Address
TCP Header then your data...
16
IP Fragmentation

• Not all routing systems utilize 1500 byte
  packets.
• PPP (dialup) sizes are 576 bytes.
• Like TCP frames, IP frames need to be reassembled
  in order even if one packet is lost.

17
IP Fragmentation
18
Subnets

• Class A 255.0.0.0
• Class B 255.255.0.0
• USU uses 255.255.255.0 for subnetting buildings
• Class C 255.255.255.0
• Subnet Masks
• 129.123.0.0/16
• 129.123.7.0/24

19
Flat vs. Routed Networks

• Flat network
• Enormous party line
• Systems move freely around enterprise
• Simple and cheap to implement
• Routed network
• Require subnetting
• Control packet flow
• Systems must readdress as they move

20
Subnetting
21
Obtaining a host address

• Number Assignment
• (http//www.networksolutions.com)
• Whois
• Number registration http//thingy.usu.edu
• Manual configuration
• Inserting IP numbers for subnet, router,
  nameserver
• Dynamic Host Configuration Protocol
• Dynamic versus Static IP addressing
• Discussed in next weeks presentation

22
ICMP

• Ping
• Router information

23
Network Address Translation (NAT)

• Protects internal systems
• Makes internal systems invisible
• Recycles Internet Addresses (IP)
• Uses nonroutable IP addresses
• 10.xxx.xxx.xxx
• 172.xxx.xxx.xxx
• 192.xxx.xxx.xxx

24
IP Version 6
25
Conversion to IPv6

• Addressing
• 3ffeffff0100f1010210a4fffee39566
• Compatibility ffffw.x.y.z
• Dual Stack
• Tunneling

26
IPv6

• Extended address capabilities
• Streamlined header
• Flow labelling
• No fragmentation or reassembly
• No header checksum (redundant)
• No options

27
Broadcasting and Multicasting

• Uncontrolled Flooding
• Copy of each packet to all neighbors
• Can cause broadcast storms
• Controlled Flooding
• Sequence number controlled flooding
• Reverse path forwarding
• Spanning Trees

28
Multicasting
29
Types of Multicast Management Protocols

• Internet Group Management Protocol
• Distance-Vector Multicast Routing Protocol
• Protocol-Independent Multicast protocol

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Applications of Multicast

• Online conferencing (mbone)
• Video
• Sound
• System Imaging
• Symantec Ghost
• Powerquest DriveImage

31
IP Layer
The End
Remember Homework 2 from the Website