Test #1 Flashcards
Packet format consists of?
consists of a base header, optional extension headers. and a payload
Describe the IPv6 Base Header
VER(version num), Traffic Class, Flow Label, Hop limit
What is flow label for?
Used in MPLS and similar protocols to provide simpler handling of all packets between a sender and receiver.
It is essentially the source and destination addresses that are cached.
A router that supports flow labels, has a flow label table.
The table has an entry for each active flow label: When a router receives a packet it checks the flow label table to find the entry for the corresponding flow.
What are rules of using flow labels?
The flow label is assigned to a packet by the source host. That flow label cannot be reused while the flow is active.
If a host does not support the flow label it simply ignores it.
All packets belonging to the same flow have the same source, same destination, same priority, and same options.
Comparison between IPv6 and IPv4
Explain Extension headers
Next header field acts as a pointer.
What are the option extension header?
Hop-by-hop
Destination
Source routing: allows the source to dictate the path to use.
Fragmentation: If a packet is too large, it is fragmented.
Authentication: Used to provide auth
ESP: Encapsulating Security Payload
Fragmentation header?
Tells that the packet is a fragment, willuse fragmentation identification to match the fragments.
The fragment offset shows where the fragment is placed relative to the start opf the fragmentable part
The M flag is used to signal when the last fragment is sent. M flag will be 0 on the last fragment.
Fragmentation can pose risks, as the endpoint has to process to reassemble the fragments. This can be used for a DOS attack.
Authentication Header?
It validates the message sender, protects against replay and ensures data inttegreity.
The keys are exchanged at the beginning of the exchange
The two modes are: tunnel and transport
Tunnel mode will create an outer IP[ header that just has the addresses if the UOsec “peers”
Encrypted Security Payload?
This also provides a transport and tunnel mode
What is dual stack
When a host is capable of implementing both IPv4 and IPv6 at the same time
What is tunnelling?
A strategy used when two computers using IPv6 communicate to eachother through a region that only handles IPv4.
The IPv6 packet will be encapsulated in an IPv4 packet.
Three types of addresses?
Unicast - Send to 1 specific address
Anycast - Send to a group of computers that all share a single address, can only be received by one address.
Multicast - Defines a group of computers, A broadcast essentially
The two types of IPv4 addresses?
In a Unique unicast message, the interface ID can be calculated using the MAC address,
What is link local block?
A subblock that is used as a private address in a network
Explain the multicast block
The first 8 bits are all 1s or all F’s which says that it is a multicast
the next 4 bits specify if transcient to permanent
Global unicast address/.
