Transcript Midterm Review - SUNYIT Computer Science Department

NCS315/TEL550
Networking of Information Systems
&
Advanced Networking Standards &
Protocols
Ronny L. Bull, MS
Lecturer
Computer Science Department
Spring 2014
Outline
• Review
– Network Layer
– Link Layer
OSI Model - A Second Look
IPv4 Packet
IPv6 Packet
ICMP (Internet Control Message Protocol)
• What is ICMP?
• What is it used for?
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description
echo reply (ping)
dest. network unreachable
dest host unreachable
dest protocol unreachable
dest port unreachable
dest network unknown
dest host unknown
source quench (congestion
control - not used)
echo request (ping)
route advertisement
router discovery
TTL expired
bad IP header
ICMP Messages
IPv4 Addressing
• What are the two types of addresses a network
recognizes?
• What form is an IPv4 address notated in?
• What form does a computer or router read?
• Can you convert between them?
• What are the ranges for the different classes?
IPv4 Addressing
• Network class determined from the first octet
IPv4 Addressing
• Class D, Class E rarely used
– (never assign them in the wild!)
– Class D: value between 224 and 239
• Reserved for multicasting
– Class E: value between 240 and 254
• Experimental use
• Eight bits have 256 combinations
– Networks use 1-254
– 0: reserved as network placeholder
– 255: reserved for broadcast
IPv4 Addressing
• What is a loopback address?
• What is it used for?
Subnet Mask
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•
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What is a subnet mask?
What is it used for?
How is it notated?
What are the ranges?
What is CIDR Notation?
Subnet Mask
IPv6 Addressing
• How is an IPv6 address formatted?
• What are some differences between IPv6 addresses
and IPv4 addresses?
Assigning IP Addresses
• What are the two ways of assigning IP addresses to
a host on a network?
• Why would you choose one over the other?
DHCP
(Dynamic Host Configuration Protocol)
• What is DHCP?
• What is the process employed by DHCP?
• Why is DHCP useful?
DHCP
(Dynamic Host Configuration Protocol)
• What are DHCP leases?
• How are they renewed?
• How are they terminated?
Private and Link-Local Addresses
• Private addresses
– Allow hosts in organization to communicate across
internal network
– Cannot be routed on a public network
• Specific IPv4 address ranges reserved for private
addresses
• Link-local address
– Provisional address
– Capable of data transfer only on
local network segment
Address Translation
• Tell me all about NAT?
• What are the different types of NAT?
• Why should we use them?
Internet Gateways
• What is a Gateway?
• How do nodes on a network know about the
gateway?
• How do they know when to use it?
Collision & Broadcast Domains
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What is a collision domain?
How is it different from a broadcast domain?
What provides isolation of collision domains?
What about broadcast domains?
Routers
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•
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What are routers?
What are the different types of routers?
What happens when a frame goes through a router?
What is a routing table?
What are routing protocols?
Can you describe the different classes of routing
protocols and name examples of each?
Types of Routers
• Interior router
– Directs data between nodes on a LAN
• Exterior router
– Directs data between nodes external to a LAN
• Border routers
– Connect autonomous LAN with a WAN
• Routing tables
– Identify which routers serve which hosts
Static vs Dynamic Routing
• Static routing
– Router configured to use specific path between
nodes
• Dynamic routing
– Automatically calculates best path between nodes
Routing Protocols
• Best path
– Most efficient route from one node to another
– Dependent on:
• Hops between nodes
• Current network activity
• Unavailable link
• Network transmission speed
• Topology
– Determined by routing
protocol
Routing Protocols
• Routing metric factors
– Number of hops
– Throughput of potential path
– Delay on a potential path
– Load (traffic)
– MTU
– Cost
– Reliability of potential path
Routing Protocols
• Router convergence time
– Time router takes to recognize best path
• Change or network outage event
– Distinguishing feature
• Overhead: burden on network to support
routing protocol
Routing Protocols
• Distance Vector
– Determine best route based on distance to
destination
– Factors
• Hops, latecny, traffic
Routing Protocols
• RIP (Routing Information Protocol)
– Only looks at number of hops between nodes
• Limit 15 hops
– Type of IGP
• Only internal
– Slower and less secure than other protocols
Routing Protocols
• RIPv2
– Generates less broadcast traffic, more secure
– 15 hop limit
– Less commonly used
Routing Protocols
• BGP (Border Gateway Protocol)
– Communicates using BGP-specific messages
– Many factors used to determine best paths
– Configurable to follow policies
– Type of EGP (Exterior Gateway Protocol
– Most complex (used for internet traffic)
Routing Protocols
• Link-state routing protocol
– Routers share information
• Each router independently maps network,
determines best path
• OSPF (Open shortest Path First
– Interior or border router use
– No hop limit
– Complex algorithm for path determination
– Each OSPF router maintains a
database containing other
routers' links
Routing Protocols
• IS-IS (Intermediate System to Intermediate System)
– Codified by ISO
– Interior routers only
– Supports two Layer 3 protocols
• IP
• ISO-specific protocol
– Less common than OSPF
Routing Protocols
• Hybrid
– Link-state and distance-vector characteristics
– EIGRP (Enhanced Interior Gateway Routing
Protocol)
• Most popular
• Cisco proprietary
– EIGRP benefits
• Fast convergence time, low network overhead
• Easy to configure
• Supports multiple protocols
• Scales well
Routing Protocols
Frames
• What does a frame header consist of?
• What devices rely on frame information in order to
forward traffic?
Frames
type
dest.
source
preamble address address
data
(payload)
CRC
Link Layer Services
• Flow control
– What is it?
• Error detection
– How is it done?
• Error correction
– How is it done?
• Half-duplex vs full-duplex
• Where are link layer services implemented?
Multiple Access
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What are TDMA and FDMA?
Explain CSMA/CD
Explain CSMA/CA
Polling vs Token Passing
What is the main thing these protocols are concerned
with managing?
ARP
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•
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•
What is ARP?
What is an ARP table?
How is the ARP table created?
What kind of entries does it consist of?
Whats happens when A wants to talk to B
through R?
A
111.111.111.111
74-29-9C-E8-FF-55
R
B
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.220
1A-23-F9-CD-06-9B
111.111.111.112
CC-49-DE-D0-AB-7D
111.111.111.110
E6-E9-00-17-BB-4B
222.222.222.221
88-B2-2F-54-1A-0F
Ethernet Topologies
• What are the two different Ethernet topologies we
discussed?
• What are their characteristics?
Switches
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What layer of the OSI model?
Are hosts aware of their presence?
How do they know where to forward packets?
What is a CAM table used for?
How is it populated?
What is it populated with?
What happens when there are multiple switches
connected together serving hosts on many
segments?
VLANS
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What are they?
Why are they used?
What is the main purpose of using VLANs?
What is the relationship between switches and
VLANs?
• Can VLANs span across multiple switches?
– How does this work?
– Do we need any special configurations?
• Can a host belong to multiple VLANs?
VLANS
type
preamble
dest.
address
source
address
data (payload)
CRC
802.1 frame
type
data (payload)
2-byte Tag Protocol Identifier
(value: 81-00)
Tag Control Information (12 bit VLAN ID field,
3 bit priority field like IP TOS)
CRC
802.1Q frame
Recomputed
CRC
MPLS
• What is it?
• How is the frame modified to support it?
• How do MPLS capable routers route traffic between
each other?
Load Balancing
• What is its purpose?
• How are data centers typically configured to perform
load balancing?
What happens when a request is made to a
web server?
• Draw out and describe the process booting up a host
and sending a web page request to google?
• How is the data sent back to the requesting host?
• Assume NAT is deployed on both ends?
– Dynamic on the requesting hosts side
– Static on google's side