What's the Problem with IPv4?
Well that depends who you ask - the answer could be "nothing" or "lots".
IPv4 was designed in the 1970's and deployed in the early 1980's. At the time the
32 bit address space seemed to be huge, however the classful based ass
Class A, B & C Networks
Initially, blocks of network addresses were allocated in three common formats:
The leftmost byte of the address specifies the network number and class, with
the first byte ranging from 1 to 126.
The leftmost two byt
Neighbour Discovery Protocol (NDP)
As mentioned in the previous lecture, one of the significant benefits of IPv6 relate
to its network discovery and autoconfiguration features. This is achieved through
the use of the Neighbour Discovery Protocol or NDP, d
Obtaining an Address Allocation
From an ISP
ISPs are allocated a block of addresses from the appropriate Regional
Internet Registry (RIR) such as ARIN, RIPE NCC or APNIC. As an aside, the
RIRs are allocated IP address space by the Internet Assigned Number
A Default Route is a special form of static route - one that is used as a last resort
when no other route exists for the destination network. These can be useful for
situations when all "external" traffic leaves the network via one connecti
Other Datagram Header Fields
Time To Live
This field specifies (in seconds) that the datagram is permitted to exist in the
internetwork. It is set to a suitable high value when the datagram is generated
and is decremented by each router that processes the
If configured, telnet or SSH can be used via one (or maybe more) of the routers
network interfaces in order to administer the router. This is how routers are
normally managed in the "real world".
SNMP can also be configured allowing for mon
The IEEE 802 standards committee wanted a way of indicating what higher level
protocol was carried by an 802.3 data packet (in Ethernet V2, the type field
already carries this information). To allow this, a newLogical Link Control layer was
What Does a Router Do?
A router forwards packets between networks, one hop closer to its intended
destination. The destination may be either a host on a directly connected network
(ie. the router can perform direct delivery) or it may need to forward the
IPv6 Extension Headers
Every IPv6 datagram has a base IPv6 header - any additional information is
provided via additionalextension headers, if required. The Next Header field is
used to indicate the type of header that follows the base header. This can be
IPv6 allows for three types of address classes:
A unicast IP address identifies a single interface (same as for IPv4).
Anycast IP addresses are identifiers for a set of interfaces, typically belonging
to different nodes. An I