Internet Basics 1 Flashcards
What is an internetwork?
- Many networks interconnected, however provide the illusion of having a single network.
Each network in an internetwork has its own what?
addressing and routing mechanism.
To cross from one network to another, in an internetwork, you need an…
additional layer of software to glue everything together.
What are the Internetwork Properties?
- You can send a message from any host to any other host in the internetwork(via intermediate routers).
- Has is own addressing mechanism and routing mechanism.
- scales to global connectivity.
What are the Individual Network Properties?
- Must be able to transfer messages between any two nodes in the network.
- Preferably must support broadcast.
What is in the Internet Protocol (IP) Service Model?
- Provides global name (and address) space
2. Provides datagram service to the transport layer(TCP, UDP).
What is specifically not in the IP Service Model?
Delivery guarantees on bandwidth, delay or loss.
What are theIP Delivery failure modes?
- Packet delayed for a very long time.
- Packer loss.
- Packet delivered more than once.
- Packets delivered out of order.
What are the IPv4 Address Model Properties?
- 32-bit address
- Hierarchical - unique network ID and unique host ID is unique with in the network.
- An IP address points to a unique network adaptor.
IP addresses have ______ to do with the particular network addresses
nothing
Ethernet addresses are….
typically hardcoded in the hardware of your machine.
Internet domain name to IP address is performed by which Service?
Domain Name Service.
Translation from IP address to the physical address is done via which Protocol?
Address Resolution Protocol (ARP)
Why is, a Fixed Table Option for IP to Physical Address Translation Design to maintain a central repository and distribute to hosts, not a good idea?
It creates a bottleneck for queries and updates.
Why is, a Hard-coded Option for IP to Physical Address Translation Design to encode the physical address in the IP address not a good idea?
It makes it impossible to associate IP address with topology (routing becomes to difficult).
Why is have a automatically generated table built by ARP at each host a good idea for IP to Physical Address Translation Design?
It removes unused entries?
Where is ARP in the protocol stack?
In-between IP and the Physical Networks.
What happens for an ARP-REQUEST?
The ARP-REQUEST is encapsulated into a physical network frame.
All machines in the physical network receive the ARP-REQUEST and learn the learn the sender physical network address.
Only the target IP address responds.
If no reply, retransmit request with exponentially increasing interval.
What is in the ARP header?
- Sender IP address field
- sender physical network address field.
- target IP address field.
- target physical network address field.
What is in the ARP-REPLY header?
- sender IP address field
- sender physical network address field
- target IP address field.
- target physical network address field.
ARP messages DO NOT
leave the LAN
For Datagram Forwarding within IP, the routing table is…
simple and static on hosts. Complex and dynamic on router.
For Datagram Forwarding within IP, the routing table contain what?
A list of pairs.
For Datagram Forwarding within IP use _____ to get hardware address of host/router
ARP
What is the IP packet format?
- 4or6-bit Version
- 4.bit header length
- 8-bit type of service (TOS)
- 16-bit total length (counted in bytes)
- 16-bit packet ID
- 3 single-bit flags
- 13-bit fragment offset into datagram.
- 8-bit time-to-live (TTL)
- 16-bit IP checksum on header
- 32-bit source IP address
- 32-bit destination IP address
- Options (variable size)
- Padding fill to 32-bit boundaries.
What is the Problem in IP Fragmentation and Reassembly?
The host does not know the minimum value for the Maximum Transmission Unit.
What is the solution for the IP Fragmentation and Reassembly problem?
Split IP packet into acceptably sized packets prior to sending over physical link.
Where does reassembly occur in IP Fragmentation and Reassembly?
At the destination to minimize refragmentation.
What happens when a fragment is damaged/lost in IP Fragmentation and Reassembly?
Drop all fragments in packet.
What configuration information does a host need?
- Its IP address
- Subnet mask
- Default router IP Address
- DNS Server IP address.
Server manage a ____ number of IP addresses.
finite
Addresses are leased to clients for ____ leases
finite
_____ lease if you need IP address longer
Renew
Dynamic Host Configuration Protocol (DHCP) is…
a simple way to automate configuration information for a host.
Network administrator does not need to enter host IP address by hand.
The Dynamic Host Configuration Protocol (DHCP) is good for what kind of networks?
Large and/or dynamic networks.
The Dynamic Host Configuration Protocol (DHCP) is layered on top of what protocol?
UDP (a simple transport protocol).
When a host powers on it sends what kind of message?
A DHCPDISCOVER message.
The DHCPDISCOVER message contain what?
The host’s physical address.
What are the 4 DHCP messages?
- Discover
- Offer
- Request
- ACK
DHCP message flow is:
- Host broadcast a DHCPDISCOVER message
- Server broadcasts DHCPOFFER to host.
- host broadcasts DHCPREQUEST to server.
- Server broadcasts DHCPACK to host.
What do the DHCP message always broadcast?
To let other servers know of the exchange occurring between the host and the server.
What if the IP Dest address were all zeros?
The ethernet is broadcast anyway.
What is the Internet Control Message Protocol (ICMP)
IP companion protocol that handles error and control messages.
What are the error messages in the Internet Control Message Protocol (ICMP)
- Host unreachable
- Reassembly failed
- IP checksum failed
- TTL exceeded (packet dropped)
- Invalid header
What are the control messages in the Internet Control Message Protocol (ICMP)
- Echo/ping request and reply
2. Route redirect.
What is a Virtual Private Network?
A group of connected network with connections between networks that do not belong to the network. With the goal to control connectivity and unified management/service.
What is a IP Tunnel
Virtual point-to-point link between an arbitrarily connected pair of nodes.
What are the advantages of IP Tunneling?
- Transparent transmission of packets.
- Only need to change relevant routers (end points)
- encryption, gives you a secure private internetwork
- End-points of tunnels my have features not available in other Internet routers.
- Useful for mobile routing (mobile IP)
What are the disadvantages of IP Tunneling?
- Increases packet size
- Processing time needed to encapsulate/decapsulate packets.
- Management at tunnel-aware routers