ece 4110 – internetwork programming tcp/ip protocol (cont’d)

ECE 4110 – Internetwork Programming

TCP/IP Protocol (cont’d)

Spring 2003Tuna Tugcu ECE 4110 – Internetwork Programming 2

DIX Ethernet Data Frame Format

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.”

Preamble(8 Bytes)

DestinationMAC Address

(6 Bytes)

SourceMAC Address

(6 Bytes)

Type(2 Bytes)

DataCRC

(4 Bytes)

Gap12 Bytes


Computer X on Network wants to send a message to Computer Y on Network .1

Routing Concepts

5

7

9

3

6

5

4

8

2

A4

ComputerX

ComputerY

FE

D

CB

A1

A

A2

1 Network Number (Address)RouterNetwork

1A3


Destination5 : Y

Source1 : X

OtherStuff

Data

IEEE 802.3 Frame

PreambleDestination

MAC Address

SourceMAC address

Length DATA CRC

Routing Concepts (cont’d)

Network address is software configurable.


Routing

Service Connection-oriented Connectionless

Delivery Direct Delivery Indirect delivery


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.


* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall

Direct Delivery

Source and the destination are on the same physical network. Address mapping is between IP and physical address of the

final destination. Physical address of the destination is found via ARP.



Indirect Delivery

Source and destination are on different networks.

Address mapping is between IP and physical address of the next hop.


Routing Methods

Next-hop routing Network-specific routing Host-specific routing Default routing



Next-Hop Routing



Network-Specific Routing


Host-Specific Routing



Default Routing



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.


Routing Table

Flags U The router is up and running. G The destination is a gateway (indirect

delivery). H Host-specific address. D Added by redirection (by ICMP). M Modified by redirection (by ICMP).


Routing Module



Routing Module (cont’d)

Search for route in this order: Direct delivery Host-specific delivery Network-specific delivery Default delivery


Routing Module (algorithm)

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

Use next-hop field in RT Else

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

19* From TCP/IP Protocol Suite, B. A. Forouzan, Prentice Hall

Example Topology


Routing Table for R1

Mask Destination Next Hop Interface255.0.0.0 111.0.0.0 - m0255.255.255.224 193.14.5.160 - m2255.255.255.224 193.14.5.192 - m1

255.255.255.255 194.17.21.16 111.20.18.14 m0

255.255.255.0 192.16.7.0 111.15.17.32 m0255.255.255.0 194.17.21.0 111.20.18.14 m0

0.0.0.0 0.0.0.0 111.30.31.18 m0


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.


Example 1 (Solution)

Direct delivery192.16.7.14 & 255.0.0.0 192.0.0.0 no

match192.16.7.14 & 255.255.255.224 192.16.7.0 no

match192.16.7.14 & 255.255.255.224 192.16.7.0 no

match Host-specific

192.16.7.14 & 255.255.255.255 192.16.7.14 no match

Network-specific192.16.7.14 & 255.255.255.0 192.16.7.0 match


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.



Direct delivery193.14.5.176 & 255.0.0.0 193.0.0.0 no

match193.14.5.176 & 255.255.255.224 193.14.5.160

match


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.



Direct delivery200.34.12.34 & 255.0.0.0 200.0.0.0 no match200.34.12.34 & 255.255.255.224 200.34.12.32 no match200.34.12.34 & 255.255.255.224 200.34.12.32 no match

Host-specific200.34.12.34 & 255.255.255.255 200.34.12.34 no match

Network-specific200.34.12.34 & 255.255.255.0 200.34.12.0 no match200.34.12.34 & 255.255.255.0 200.34.12.0 no match

Default200.34.12.34 & 0.0.0.0 0.0.0.0 match


Example 4

Make the routing table for router R1


Mask Destination Next Hop Interface

255.255.0.0 134.18.0.0 - m0

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



Example 5

Make the routing table for router R1


Mask Destination Next Hop Interface255.255.255.0 200.8.4.0 - m2

255.255.255.0 80.4.5.0 201.4.10.3 m1or 200.8.4.12 or m2

255.255.255.0 80.4.6.0 201.4.10.3 m1 or 200.4.8.12 or m2

0.0.0.0 0.0.0.0 ???????????? m0



Example 6

Given the routing table in the next slide, draw the topology.


Mask Destination Next Hop Interface255.255.0.0 110.70.0.0 - 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

Example 6 (cont’d)

ece 4110 – internetwork programming tcp/ip protocol (cont’d)

Documents

tuna tugcu ece

physical address

bytes slide

address mapping

bytes destination mac

broadcast address

bytes source mac address

prentice hall slide