Networking Exam 2

How can we go from an IPv4 address to an IPv6 address?

IPv4 goes at the end of the IPv6 address

inter-as routing

large - VGP

Explain number of network/host bits that make up a class A, B, C network

A - 8 B - 16 C - 24

router

Node that interconnects networks. Often called a gateway. It is a network layer device because it works with IP addresses and connects heterogeneous networks based off of different data link protocols. It maintains routing tables and implements routing algorithms.

link-state routing

OSPF is an example Tells every other node its distance to neighbors

switching fabrics

Part of how routers are selected, specifically memory, bus, and crossbar.

distance-vector routing

RIP is an example Tells neighbors its distance to every other node

hub

Repeats incoming signals out of all outgoing ports (like a repeater) Backbone hub interconnects LAN segments Extends max distance between nodes But individual segment collision domains become one large collision domain physical layer devices that amplify signals out of all their ports

VLAN

VLANs separate the collision domain as well as the broadcast domain Hosts in each VLAN are in the same Virtual LAN "Color coded" "Trunks" carry multiple VLANs between switches Data on a VLAN is separated from other data virtual local area network. devices are on different networks, but they act like they are on the same switch and network.

connection-oriented approach to circuit switching

Virtual Circuit Switching requires set up and tear down of the circuit after each use. No one else can use any of the bandwidth during an active session—even if it is idle!

autonomous system (AS)

a network that some single entity maintains

loopback address

address that all computers have that means myself 127.0.0.1 also known as localhost

subnet ID

after it goes through subnet mask

IP packet delivery model

connectionless, best-effort packet-switched network

network address translation (NAT)

deals with private IP addresses that are not globally routable

flooding (with switches)

forward on all but the interface on which the frame arrived happens as part of switch self learning algorithm. It does flooding where it sends packet out of all of its ports if it doesn't know where the destination is.

What is the difference between routing and forwarding?

forwarding constructs forwarding tables. Routing deals with figuring that out in the first place

broadcast address

general broadcast - a host turns on for the first time. Is all 1's. 255.255.255.255 and sends it out to all interfaces on the network. Routers typically do not forward this, switches will. local broadcast - use network id at the beginning and all 1's at the end

four basic components to a router architecture

input ports, output ports, switching fabric, routing processor

types of switching fabrics

memory, bus, crossbar

forwarding table

much simpler than routing table. says if i have a destination, what output port should i use. both routers and switches have forwarding tables

subnet mask

network + subnet is all 1s and rest are 0s

asymmetric routing

occurs when packets take one route from sender to receiver, but take a different route from receiver to sender occurs on packet switching networks where you might send a packet through a certain route and the reply packet could come from a completely different route

classful addressing scheme

old way that the iama used to give out ip addresses. class a, b, and c networks

virtual circuit identifier (VCI)

part of circuit switching networks

How can we go from an Ethernet MAC address to an IPv6 address?

put fffe in the middle split the address and put half at the beginning and half at the end

longest-prefix match

route to network with the most matching host bits if two subnets will yield a match

border gateway protocol (BGP) - inter-as routing protocol

routing in the large between autonomous systems

intra-as routing

routing in the small

gateway

special kind of router that sends things out of your networking area

Bridge (switch)

stores and forwards Ethernet frames examines frame header and selectively forwards frame based on MAC dest address when frame is to be forwarded on segment, uses CSMA/CD to access segment transparent hosts are unaware of presence of bridges plug-and-play, self-learning bridges do not need to be configured

multi-homed host

the host with a couple network interface cards in it. laptops can have ethernet and wireless connections, for example

What does the :: mean in an IPv6 address?

there are 0's in between

queueing delay

there is a lineup of packets to be sent out of a router. The routers only have so much memory and can drop packets. Part of latency and nearly impossible to predict.

open shortest path first (OSPF)

type of link-state routing algorithm Tells every other node its distance to neighbors Internal router :: a level 1 router. Backbone router :: a level 2 router. Area border router (ABR) :: a backbone router that attaches to more than one area. AS border router :: (an interdomain router), namely, a router that attaches to routers from other ASs across AS boundaries. Internal router :: a level 1 router. Backbone router :: a level 2 router. Area border router (ABR) :: a backbone router that attaches to more than one area. AS border router :: (an interdomain router), namely, a router that attaches to routers from other ASs across AS boundaries. v

maximum transmission unit (MTU)

vary by underlying physical medium, telephone wires, ethernet, fibernet

Be able to explain certain IP packet format fields (version, ident, TTL, checksum)

version - 4 and 6 ident - dealt with fragmenting packets and shows how to put them back together TTL (time to live) - gets decremented for every router that it visits. if it goes to 0, it is dropped. Usual value is 64. checksum -

How large is an IPv6 address?

very large (don't memorize number)

Need for a spanning tree algorithm

It solves loops in bridges by shutting off certain connections.

Explain the reason for the ARP and DHCP protocols

ARP - translation between IP address and MAC address DHCP - deals with how do we get an ip address if we are powered on for the first time. ask for a server for an ip address.

internetwork

An arbitrary collection of networks interconnected to provide some sort of host-host packet delivery service

CIDR

Can use any number of bits for network ip networks

packet switching

Data networks, uses datagrams Enables packets to be sent from one host to another without a direct or dedicated physical connection. Asymmetric routing common the general Internet uses this. Connections aren't necessarily set up ahead of time, we send out packets and hope for the best. Routers decide the route that the packets will take. Routers can change the route if something changes in the connections.

connectionless/datagram approach to packet switching

Every packet contains enough information to enable any switch to decide how to get it to destination Every packet contains the complete destination address

root bridge (spanning tree protocol)

For increased reliability, desirable to have redundant, alternative paths from source to dest But we don't want the loop problem! Solution: organize bridges in a spanning tree by disabling subset of interfaces Protocol used by set of bridges to agree upon a spanning tree for a particular LAN Each bridge decides the ports over which it is and is not willing to forward frames Algorithm is dynamic Bridges may reconfigure themselves into a new spanning tree should some bridge fail

Bridge advantages over hubs

Hubs operate at the physical layer. They only repeat signals. Bridges make informed switching decisions using link layer addresses (typically MAC addresses). Bridges isolate collision domains resulting in higher total max throughput. They have a limitless number of nodes and geographical coverage. Bridges can connect different Ethernet types. There is no configuration necessary.

What are some of the reasons we are trying to move to IPv6?

IPv4 addresses have become relatively scarce NATs help by promoting reuse of address space, but they don't do enough The public IPv4 address space will eventually be depleted. It would be nice to not have to rely on protocols like DHCP to configure addresses Private communication over a public medium like the Internet requires encryption services that protect the data being sent from being viewed or modified in transit. IPv6 is required to include IPsec. IPsec allows authentication, encryption, and compression of IP traffic. IPv6 uses a 128-bit address instead of the 32-bit address of IPv4.

Circuit switching

Most commonly used in telephone networks Physical connection is set up from one end to the other Data is transmitted, Connection is torn down Circuit switching dedicates fixed amount of bandwidth from one end to another switching - you move a packet from one switch to another, in one input port and out another Set up a complete path before you complete a transaction and follow exactly that path. once it is set up it guarantees a connection

routers compared to switches

Routers are network layer devices. Switches are link layer devices. Routers maintain routing tables and implement routing algorithms. Bridges maintain bridge tables, implement filtering, learning, and spanning tree algorithms. With bridges, operation is simpler requiring less packet processing. Bridge tables are self learning. All bridge traffic is confined to a spanning tree, even when alternative bandwidth is available. Bridges do not offer protection from broadcast storms. Routers provide protection against broadcast storms. Routers require IP address configuration (not plug and play). Routers require higher packet processing. Bridges do well in small while routers are used in large networks.

different types of ASs

Stub AS, Multihomed AS, Transit AS