3213 DataLink+Network Flashcards
How does a network layer packet travel
In terms of Layer structure
Sender: Network layer takes segments from transport layer, encapsulates to packet and pass to data link
Intermediate Router: Packets routed through intermediate nodes/routers
Receiver: Receive packet from lower layers, extracts and pass to transport.
Routing Algorithm used for what
Determine path of packets
Internet protocol (IP) pros/cons
Pros: Best effort connectionless delivery
Keep routers simple
Cons: Unreliable, packets may be lost, out of order, duplicated
No throughput guarantee, no delay guarantee, no QoS guarantee
Higher layer handles issues
IP Addressing—Network Layer Address
Interface: Connection between host/router and physical link (aka. port)
IP address: Each interface must have a globally unique IP address.
router usually has multiple ip addresses for each interface. Host usually has 1.
IP Addressing prefix + suffix
Host ID 0 and 1
Prefix defines network
Suffix defines connection to the node
If Host ID all 0s: used to identify network address
If all 1’s, used to broadcast to all nodes.
IP address notation
4 bytes of IP address (4 octets)
eg. 00000000 00000000 00000000 00000000
Such that 11111111 represents 255 max
Classful Addressing
Divide entire IPv4 address into 5 classes labeled A,B,C,D,E. Each class has different size for different types of networks.
Draw diagram on cheatsheet !!
Subnet Addressing + interfacing
For easier management, large network may partition into smaller networks called subnets
Subnet can interface physically without intermediate router
Subnet: How does it work
Add another level of hierarchy to IP address
‘network prefix + subnet number + host number’
Only visible within organization
Subnet Mask: Usage + How to use
To find length of network prefix use subnet mask : w.x.y.z
Bits corresponding to network prefix are set to 1, and 0 otherwise.
Subnet range calculations
Given the added mid-fix of a subnet, we have n amounts of subnets, with n hosts in each. Say 11 bits for host, we can have 2^11 hosts, then MINUS 2 to save 0’s for network address, and 1’s for broadcast address
Creating subnet for # of hosts
Given x bits for Host ID, subtract 2^n to get amount of hosts needed for each subnet.
Now subtract n bits from Host bits, and add it to the Network bit range.
Apply mask to network ID, and the last few bits of 2^n represent starting point for subnet hosts.
Solutions to IPv4 Exhaustion
Classless InterDomain Routing (CIDR):
- short term sol. Reduce waste in address allocation.
Network Address Translation(NAT):
- Single machine/router with an ip address representing many computers behind it.
IPv6: 128 bit space
Classless interdomain routing
Abandon notion of classful addressing
Key concept: length of network id prefix can be any length.
pros: high flexibility and scalability
a.b.c.d/x, where x reps # of leftmost bits for network id
Network address translation
Private IP addresses for private internet
Private IP addresses not forwarded to internet, therefore different priv nets can re-use same private ip addresses.
Only 1 ip address is required from ISP to support whole private network to connect to internet.
1 IP for router, but specify port for hosts
