Download Lecture3 - Lane Thames

ECE 4110 –
Internetwork Programming
TCP/IP Protocol
(cont’d)
DIX Ethernet Data Frame Format
Destination
Source
Preamble
MAC Address MAC Address
(8 Bytes)
(6 Bytes)
(6 Bytes)
Type
(2 Bytes)
Data
CRC
(4 Bytes)
Gap
12 Bytes
Preamble: Alternating 0’s and 1’s with last bit a l.

Destination medium access control (MAC) address: Each receiver DL layer
compares this to its own hardwired network interface card (NIC) address.

Normally a NIC knows its own address and the broadcast address.

Source MAC address: Sender’s NIC address.

Type: Type of data transporting. E.g.: Internet Protocol.

Cyclic Redundancy Check: Used for checking data integrity.

Gap: After the Ethernet Frame, a 12 Byte Interframe Gap must always
follow.
Note: Receiver DL layer does not look at data.
Note: Data is in most network technologies called a “packet.”

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ECE 4110 – Internetwork Programming
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Routing Concepts
B
3
Computer
X
Computer
Y
4
2
9
A1
A2
A4
1
5
A
A3
6
8
7
F
1
C
D
E
Network Number (Address)
Router
Network
Computer X on Network 1 wants to send a message to Computer Y on Network 5 .
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Routing Concepts
IEEE 802.3
Frame
Preamble
Destination
Source
Length
MAC Address MAC address
Destination
5:Y

(cont’d)
Source
1:X
DATA
Other
Stuff
CRC
Data
Network address is software configurable.
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Routing

Service



Connection-oriented
Connectionless
Delivery


Direct Delivery
Indirect delivery
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Connection-Oriented vs.
Connectionless


In connection-oriented services,
the network layer protocol
first makes a connection.
In connectionless services, each
packet is treated independently. So,
there is no relationship between the
packets.
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Direct Delivery

Source and the destination are on the same physical network.
Address mapping is between IP and physical address of the

Physical address of the destination is found via ARP.

final destination.
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Indirect Delivery


Source and
destination are
on different
networks.
Address mapping
is between IP
and physical
address of the
next hop.
Spring 2003
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Routing Methods




Next-hop routing
Network-specific routing
Host-specific routing
Default routing
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Next-Hop Routing
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Network-Specific Routing
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Host-Specific Routing
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
12
Default Routing
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Static vs. Dynamic Routing


In static routing, routing table is
constructed manually.
In dynamic routing, routing table is
constructed automatically using
protocols like RIP, OSPF, or BGP.
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Routing Table

Flags





U
G
H
D
M
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The router is up and running.
The destination is a gateway (indirect delivery).
Host-specific address.
Added by redirection (by ICMP).
Modified by redirection (by ICMP).
ECE 4110 – Internetwork Programming
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Routing Module
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* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
ECE 4110 – Internetwork Programming
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Routing Module

(cont’d)
Search for route in this order:




Direct delivery
Host-specific delivery
Network-specific delivery
Default delivery
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Routing Module

For each entry in RT:


Apply the mask to destination address
If result of mask matches the destination field in the entry
in RT, find next-hop address as follows:

If G flag is set


Else





(algorithm)
Use next-hop field in RT
Use destination address in the packet (direct delivery)
Send packet to fragmentation module with the next-hop
address
Stop
Else, send ICMP error message
Stop
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Example Topology
19
* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall
Routing Table for R1
Mask
255.0.0.0
255.255.255.224
255.255.255.224
Destination
111.0.0.0
193.14.5.160
193.14.5.192
Next Hop
-
255.255.255.255
194.17.21.16
111.20.18.14
m0
255.255.255.0
255.255.255.0
192.16.7.0
194.17.21.0
111.15.17.32
111.20.18.14
m0
m0
0.0.0.0
0.0.0.0
111.30.31.18
m0
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ECE 4110 – Internetwork Programming
Interface
m0
m2
m1
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Example 1

Router R1 receives 500 packets for
destination 192.16.7.14; the algorithm
applies the masks row by row to the
destination address until a match
(with the value in the second column)
is found.
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Example 1 (Solution)

Direct delivery
192.16.7.14 & 255.0.0.0
192.16.7.14 & 255.255.255.224
192.16.7.14 & 255.255.255.224

no match
no match
no match
 192.16.7.14
no match
 192.16.7.0
match
Host-specific
192.16.7.14 & 255.255.255.255

 192.0.0.0
 192.16.7.0
 192.16.7.0
Network-specific
192.16.7.14 & 255.255.255.0
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Example 2

Router R1 receives 100 packets for
destination 193.14.5.176; the
algorithm applies the masks row by
row to the destination address until a
match is found.
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Example 2 (Solution)

Direct delivery
193.14.5.176 & 255.0.0.0
193.14.5.176 & 255.255.255.224
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 193.0.0.0
 193.14.5.160
ECE 4110 – Internetwork Programming
no match
match
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Example 3

Router R1 receives 20 packets for
destination 200.34.12.34; the
algorithm applies the masks row by
row to the destination address until a
match is found.
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Example 3 (Solution)

Direct delivery
200.34.12.34 & 255.0.0.0
200.34.12.34 & 255.255.255.224
200.34.12.34 & 255.255.255.224

 200.34.12.34
no match
 200.34.12.0
 200.34.12.0
no match
no match
 0.0.0.0
match
Network-specific
200.34.12.34 & 255.255.255.0
200.34.12.34 & 255.255.255.0

no match
no match
no match
Host-specific
200.34.12.34 & 255.255.255.255

 200.0.0.0
 200.34.12.32
 200.34.12.32
Default
200.34.12.34 & 0.0.0.0
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Example 4

Make the routing table for router R1
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Example 4 (Solution)
Mask
Destination
255.255.0.0
134.18.0.0
255.255.0.0
129.8.0.0
222.13.16.40
m1
255.255.255.0
220.3.6.0
222.13.16.40
m1
0.0.0.0
0.0.0.0
134.18.5.2
m0
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Next Hop
Interface
-
m0
ECE 4110 – Internetwork Programming
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Example 5

Make the routing table for router R1
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Example 5 (Solution)
Mask
255.255.255.0
Destination
200.8.4.0
Next Hop
-
255.255.255.0
80.4.5.0
201.4.10.3
or 200.8.4.12
m1
or m2
255.255.255.0
80.4.6.0
201.4.10.3
or 200.4.8.12
m1
or m2
0.0.0.0
0.0.0.0
????????????
m0
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ECE 4110 – Internetwork Programming
Interface
m2
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Example 6

Given the routing table in the next
slide, draw the topology.
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Example 6
(cont’d)
Mask
255.255.0.0
Destination
110.70.0.0
Next Hop
-
Interface
m0
255.255.0.0
180.14.0.0
-
m2
255.255.0.0
190.17.0.0
-
m1
255.255.0.0
130.4.0.0
190.17.6.5
m1
255.255.0.0
140.6.0.0
180.14.2.5
m2
0.0.0.0
0.0.0.0
110.70.4.6
m0
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Example 6 (Solution)
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