CT320: Network and System Administration

Fall 2018

Routing

See this page as a slide show

CT320 Routing

Thanks to:

for the contents of these slides.

The Internet Network layer

Remember the layers?

The Internet Network layer

Host, router network layer functions:

IP Fragmentation & Reassembly

IP Fragmentation and Reassembly Example

Original:

length=4000IDfragflag=0offset=0

Fragments:

length=1500IDfragflag=1offset=0
length=1500IDfragflag=1offset=185
length=1040IDfragflag=1offset=370

(185 = 1480 / 8)

Joke

(Well, it’s the setup to a joke.)

is to packet IP delivered An a bar …
An IP packet is delivered to a bar …

Hierarchical Addressing: Route Aggregation

How it’s not done:

┌─────────────┐       ┌────────┐    ┌────────┐       ┌──────────────┐
│ 192.0.2.4   │·······│ ISP #1 │    │ ISP #2 │·······│ 203.0.113.42 │
└─────────────┘   :   └────────┘    └────────┘   :   └──────────────┘
┌─────────────┐   :      :                :      :   ┌──────────────┐
│ 203.0.113.8 │···:      :  ┌──────────┐  :      :···│ 192.0.2.88   │
└─────────────┘   :      ···│ Internet │···      :   └──────────────┘
┌─────────────┐   :         └──────────┘         :   ┌──────────────┐
│ 192.0.2.66  │····               :              ····│ 203.0.113.17 │
└─────────────┘                   :                  └──────────────┘

Hierarchical Addressing: Route Aggregation

How it’s done:

┌────────────┐       ┌────────┐    ┌────────┐       ┌──────────────┐
│ 192.0.2.4  │·······│ ISP #1 │    │ ISP #2 │·······│ 203.0.113.42 │
└────────────┘   :   └────────┘    └────────┘   :   └──────────────┘
┌────────────┐   :      :                :      :   ┌──────────────┐
│ 192.0.2.88 │···:      :  ┌──────────┐  :      :···│ 203.0.113.8  │
└────────────┘   :      ···│ Internet │···      :   └──────────────┘
┌────────────┐   :         └──────────┘         :   ┌──────────────┐
│ 192.0.2.66 │····               :              ····│ 203.0.113.17 │
└────────────┘                   :                  └──────────────┘

This scales nicely.

Hierarchical Addressing: More Specific Routes

┌────────────┐     ┌────────┐  ┌────────┐······················
│ 192.0.2.4  │·····│ ISP #1 │  │ ISP #2 │                     :
└────────────┘  :  └────────┘  └────────┘·:  ┌──────────────┐ :  ┌────────────┐
┌────────────┐  :    :               :    :··│ 203.0.113.42 │ ···│ 192.0.2.11 │
│ 192.0.2.88 │··:    :  ┌──────────┐ :    :  └──────────────┘ :  └────────────┘
└────────────┘  :    ···│ Internet │··    :  ┌──────────────┐ :  ┌────────────┐
┌────────────┐  :       └──────────┘      :··│ 203.0.113.8  │ :··│ 192.0.2.22 │
│ 192.0.2.66 │···             :           :  └──────────────┘ :  └────────────┘
└────────────┘                :           :  ┌──────────────┐ :  ┌────────────┐
                                          ···│ 203.0.113.17 │ ···│ 192.0.2.97 │
                                             └──────────────┘    └────────────┘

Hierarchical Addressing

IP Addressing: ICANN

Addressing at CSU

Hierarchy at CSU

Hierarchy at CSU

┌───────────────┐     ┌──────────┐        ┌────────┐     ┌───────────────┐
│ 129.82.40.123 │·····│ Business │        │   CS   │·····│ 129.82.44.12  │
└───────────────┘  :  └──────────┘        └────────┘  :  └───────────────┘
┌───────────────┐  :      :   ┌────────────┐   :      :  ┌───────────────┐
│ 129.82.43.4   │··:      ····│ CSU router │····      :··│ 129.82.45.85  │
└───────────────┘  :          └────────────┘          :  └───────────────┘
┌───────────────┐  :                :                 :  ┌───────────────┐
│ 129.82.42.66  │···          ┌────────────┐          ···│ 129.82.45.234 │
└───────────────┘             │    FRGP    │             └───────────────┘
                              └────────────┘ 

IP datagram format, redux

 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Version IHL Type of service Total length
Identification Flags Fragment offset
Time to live Protocol Header checksum
Source IP address
Destination IP address
Options (optional)
IP data payload (many bytes)

ICMP: Internet Control Message Protocol

TypeCodeDescription
00echo reply (ping)
30dest network unreachable
31dest host unreachable
32dest protocol unreachable
33dest port unreachable
36dest network unknown
37dest host unknown
80echo request (ping)
90router advertisement

Ping

Ping examples

$ ping -c1 google.com
PING google.com (172.217.2.14) 56(84) bytes of data.
64 bytes from den16s03-in-f14.1e100.net (172.217.2.14): icmp_seq=1 ttl=56 time=2.38 ms

--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 2.389/2.389/2.389/0.000 ms

$ ping -c1 tuba
PING tuba.cs.colostate.edu (10.1.44.62) 56(84) bytes of data.
64 bytes from tuba.cs.colostate.edu (10.1.44.62): icmp_seq=1 ttl=63 time=0.279 ms

--- tuba.cs.colostate.edu ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.279/0.279/0.279/0.000 ms

Traceroute and ICMP

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Modified: 2018-08-02T12:23

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