1. Network Layer in the Internet (3)
Internet is an interconnected collection of many networks that is held together by the IP protocol
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

2. The IPv4 (Internet Protocol) header.
The IP Protocol
The IPv4 (Internet Protocol) header.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

3. IP Addresses IP address formats.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

4. IP Addresses (2) Special IP addresses.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

5. IP Addresses (2) – Subnets
Subnetting splits up IP prefix to help with management
Looks like a single prefix outside the network
Check the size of the different subnets:
Prefix has 2^16=32K addresses, CS subnet is largest, 2^15=16K addresses, EE subnet has 2^14=8K addresses, Art has 2^13=4K addresses.
There are 4K addresses left over. What is the prefix? It is found by writing the address ranges out to see that /19 is left.
Can the prefix lengths just be changed between EE/CS/Art? No, then blocks of size 2^N would not always be aligned on a 2^N boundary.
ISP gives network
a single prefix
Network divides it into subnets internally
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6. Network Masks Class A: 255.0.0.0 Class B: 255.255.0.0
A network mask helps you know which portion of the address identifies the network and which portion of the address identifies the node. Class A, B, and C networks have default masks, also known as natural masks, as shown here:
Class A:
Class B:
Class C:
An IP address on a Class A network that has not been subnetted would have an address/mask pair similar to:
To see how the mask helps you identify the network and node parts of the address, convert the address and mask to binary numbers. = =
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

7. −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− net id | host id
Once you have the address and the mask represented in binary, then identifying the network and host ID is easier. Any address bits which have corresponding mask bits set to 1 represent the network ID. Any address bits that have corresponding mask bits set to 0 represent the node ID. = =
−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
net id | host id
netid = = 8
hostid = =
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

8. −−−−−−−−−−−−−−−−−−−−−−−−------------------−−|sub|−−−−
In order to subnet a network, extend the natural mask using some of the bits from the host ID portion of the address to create a subnetwork ID. For example, given a Class C network of which has a natural mask of , you can create subnets in this manner: − −
−−−−−−−−−−−−−−−−−−−−−−−− −−|sub|−−−−
By extending the mask to be , you have taken three bits (indicated by "sub") from the original host portion of the address and used them to make subnets. With these three bits, it is possible to create eight subnets. With the remaining five host ID bits, each subnet can have up to 32 host addresses, 30 of which can actually be assigned to a device since host ids of all zeros or all ones are not allowed (it is very important to remember this). So, with this in mind, these subnets have been created.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

9. host address range 1 to 30
host address range 33 to 62
host address range 65 to 94
host address range 97 to 126
host address range 129 to 158
host address range 161 to 190
host address range 193 to 222
host address range 225 to 254
Note: There are two ways to denote these masks. First, since you are using three bits more than the "natural“ Class C mask, you can denote these addresses as having a 3−bit subnet mask. Or, secondly, the mask of can also be denoted as /27 as there are 27 bits that are set in the mask. This second method is used with CIDR. Using this method, one of these networks can be described with the notation prefix/length.
For example, /27 denotes the network When appropriate the prefix/length notation is used to denote the mask throughout the rest of this document.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

10. netA: 204.15.5.0/27 host address range 1 to 30
Examples
Given the Class C network of /24, subnet the network in order to create the network in Figure 1 with the host requirements shown.
Solution :
It is required to create five subnets. The largest subnet must support 28 host addresses.
You can start by looking at the subnet requirement. In order to create the five needed subnets you would need to use three bits from the Class C host bits. Two bits would only allow you four subnets (22).
Since you need three subnet bits, that leaves you with five bits for the host portion of the address. How many hosts does this support? 25 = 32 (30 usable). This meets the requirement.
Therefore you have determined that it is possible to create this network with a Class C network. An example of how you might assign the subnetworks is:
netA: /27 host address range 1 to 30
netB: /27 host address range 33 to 62
netC: /27 host address range 65 to 94
netD: /27 host address range 97 to 126
netE: /27 host address range 129 to 158
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

11. IP Version 6 (1)
IPv6 protocol header has much longer addresses (128 vs. 32 bits) and is simpler (by using extension headers)
Major upgrade in the 1990s due to impending address exhaustion, with various other goals:
Support billions of hosts
Reduce routing table size
Simplify protocol
Better security
Attention to type of service
Aid multicasting
Roaming host without changing address
Allow future protocol evolution
Permit coexistence of old, new protocols, …
Deployment has been slow & painful, but may pick up pace now that addresses are all but exhausted
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011

12. The IPv6 fixed header (required).
The Main IPv6 Header
The IPv6 fixed header (required).
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

13. Extension Headers IPv6 extension headers. 5-69
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

14. The hop-by-hop extension header for large datagrams (jumbograms).
Extension Headers (2)
The hop-by-hop extension header for large datagrams (jumbograms).
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

15. The extension header for routing.
Extension Headers (3)
The extension header for routing.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

16. Internet Control Protocols (1)
IP works with the help of several control protocols:
ICMP is a companion to IP that returns error info
Required, and used in many ways, e.g., for traceroute
ARP finds Ethernet address of a local IP address
Glue that is needed to send any IP packets
Host queries an address and the owner replies
DHCP assigns a local IP address to a host
Gets host started by automatically configuring it
Host sends request to server, which grants a lease
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011

17. CDR – Classless InterDomain Routing
A set of IP address assignments.
5-59
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

18. NAT – Network Address Translation
Placement and operation of a NAT box.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

19. Internet Control Message Protocol
The principal ICMP message types.
5-61
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

20. ARP– The Address Resolution Protocol
Three interconnected /24 networks: two Ethernets and an FDDI ring.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

21. Dynamic Host Configuration Protocol
Operation of DHCP.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011

22. Useful Links
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011