10 - IP Protocol

Question 1

Routing vs Forwarding

Answer 1

Routing: determine the path taken by packets as they flow from sender to receiver (Routers have algorithms/forwarding tables)

Forwarding: move packets from router’s input to appropriate output

Question 2

IP Addresses

Answer 2

32 bit identifier for host, router interface

Question 3

Interface:

Answer 3

Connection (boundary) between host/router and physical link.

Question 4

Subnets

Answer 4

IP Addr: subnet part (high order bits) and host part (low order bits)

Creates separate virtual networks on same router

128. 6.101.0/24 (/24 is called a subnet mask) means all addresses which have the first 24 bits equal to 128.6.101, i.e. addresses 128.6.101.0 to 128.6.101.255. Also written
129. 6.101.x or 128.6.101.xxx.

Question 5

CIDR

Answer 5

Classless InterDomain Routing

• subnet portion of address of arbitrary length
• address format a.b.c.d/x where x is # bits in subnet portion

Question 6

DHCP

Answer 6

Dynamic Host Configuration Protocol
Lease an IP address from a server when it joins a network

Can return default gateway
name and ip of local DNS
network mask

Question 7

ICANN

Answer 7

Internet Coporation for Assigned Names and Numbers

Allocates addresses
Manages DNS
Assigns domain names

Question 8

NAT

Answer 8

Network Address Translation

Several devices on a local network can share one IP address, reducing the IPv4 shortage

BUT
routers should only process up to lyr 3
violates end to end agreement
address shortage should be solved by IPv6

Question 9

IPv4

Answer 9

• Version = 4 bits for IPv4
• Header Length (4 bits): in multiples of 32 bit words
• Type of Service
• Datagram length (16 bits): in bytes
• Identifier, flags, fragmentation offset
• Time to live (number of hops allowed between routers)
• Upper layer protocol: 6 for TCP, 17 for UDP, 1 for ICMP
• Header checksum
• Source + Destination
• Options
• Data

Question 10

MTU

Answer 10

Maximum Transmission Unit

Max size of payload in link layer frame. FOr ethernet 1500B, so IP datagram length at most 1500

Question 11

ICMP

Answer 11

Internet COntrol Message Protocol

Used to report errors

Question 12

IPv6

Answer 12

• Version (4bits) = 6
• Traffic class: similar to Type Of Service
• FLow label
• Payload length (16bits)
• Next header: same as upper layer protocol
• Hop limit: time to live
• SOurce/Dest IP addr 128 bits each

Question 13

IPv6 vs IPv4

Answer 13

• IPv6 has 128bits
• IPv6 fixed header length: 40 bytes
• IPv6 no fragmentation allowed
• IPv6 no header checksum to save time
• ICMPv6: additional msg types and multicast group management functions