Transcript Cs4720d

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
test
Virtual Circuits
• Connection Oriented
• Connection state information
• Phases
– VC Setup
– Data Transfer
– VC Teardown
Datagram Networks
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Internet
Not connection oriented
No guarantee of delivery
Faster
Routing
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Address 129.123.3.0
Address 129.123.7.0
Address 129.123.7.40
Address 129.123.63.0
Address 129.123.73.0
Interface 0
Interface 1
Interface 2
Interface 3
Interface 4
Routers
Router Switching
Queueing
• Packet Scheduling
• Quality of Service
• Active Queue Management
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)
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
Router Monitoring
• Traceroute (tracert)
– Simple routing test
• USU’s Web site for monitoring:
http://pomoxis.usu.edu/~network/grapher.cgi?target=%2Fnetwork-devices%2Frouter-interfaces
• What’s UP
http://floyd.usu.edu
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
Internet Addressing
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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
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
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...
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.
IP Fragmentation
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
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
Subnetting
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
ICMP
• Ping
• Router information
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
IP Version 6
Conversion to IPv6
• Addressing
– 3ffe:ffff:0100:f101:0210:a4ff:fee3:9566
– Compatibility: ::ffff:w.x.y.z
• Dual Stack
• Tunneling
IPv6
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Extended address capabilities
Streamlined header
Flow labelling
No fragmentation or reassembly
No header checksum (redundant)
No options
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
Multicasting
Types of Multicast Management Protocols
• Internet Group Management Protocol
• Distance-Vector Multicast Routing Protocol
• Protocol-Independent Multicast protocol
Applications of Multicast
• Online conferencing (mbone)
– Video
– Sound
• System Imaging
– Symantec Ghost
– Powerquest DriveImage
IP Layer
The End
Remember Homework 2 from the Website