8 - Internet & TCP/IP Flashcards
Requirements of Internetworking (4)
- provide a link between networks
- provide routing and delivery of data between process on different networks
- provide an accounting service to keep track
- accommodate the differences between different sub-networks
RFCs
Requests for Comments
TCP/IP Protocol Architecture incl. matching OSI model layer
- (7-5) 4 Application
- (4) 3 Transport
- (3) 2 Internet
- (1-2) 1 Network Access
Role of Network Access from TCP/IP
route date between hosts on the same network
Role of Internet from TCP/IP
route data across multiple networks and hosts
Roles of classes in TCP/IP Addr ?
Leading bits
- A - 0
- B - 10
- C - 110
- D - 1110 (multicast)
- E - 11110 (reserved)
Addr are encoded via the …
… MSB
CIDR
- Classless Inter Domain Routing
CIDR reasons
Allows us to subnet IP addr for
- performance
- administration
Calculating same subnet
- Perform logic AND between addr and subnet mask
CIDR uses (3)
- routing tables
- configuring firewalls
- security services
ARP
Addr Resolution Protocol
Reason for ARP?
Allows a host to discover the mapping for a given IP addr by maintaining a table
ARP Packet Outline
Dest addr -> src addr -> type -> ARP req or repl -> padding -> CRC
ARP Method (3)
- Hosts wants to find eth addr of a gateway
- ARP is broadcasted, all hosts receive packet and update tables
- Gateway replies with OpCode 2 and appropriate fields
Types of IP config
State + Dynamic
DHCP (3)
Dynamic Host Configuration Protocol
- Dynamic: allocates IP addr on a lease
- Auto: remembers IP addr for MAC
- Static: fixed IP addr
DHCP Connection
Disc -> Offer -> Req -> ACK -> ARP
ICMP
Internet Control Message Protocol
- allows host and routers to discover and communicate characteristics of the network
ICMP Ping
Echo request to see if connected
ICMP Traceroute (5)
- UDP packet sent to address with TTL of 1
- 1st route decrements TTL and send back expired packet
- Sender then knows RTT
- Sends out UDP packet with TTL incremented by 1
- Eventually reaches unreachable port
