CEG 2400 FALL 2012
Chapter 6
Network Hardware, Switching, and Routing
1
NICs (Network Interface Cards)
• Connectivity device (Common to every networking
device)
– Transceiver
• Transmits and receives data
• Enable device transmission
• Operates at the Physical and Data Link layer
– Issue data signals
– Assemble and disassemble data frames
– Interpret physical addressing information
• Determines if client can transmit data
• Do not analyze information
– Added by Layers 3 through 7 OSI model protocols
2
NICs (Network Interface Cards)
• NIC dependencies
–
–
–
–
Access method (EX. Ethernet)
Network transmission speed (1 Gbps)
Connector interfaces (RJ-45)
Method of connecting to the computers motherboard
3
How NICs connect
• Bus - signaling pathway in computer
– Motherboard uses bus to transmit data to computer’s
components
• Memory, processor, hard disk, NIC
– Differ according to capacity
• Defined by data path width and clock speed
– Data path size
• Parallel bits transmitting at any given time
• Proportional to attached device’s speed
4
5
How NICs connect
• Expansion slots- Multiple electrical contacts on
motherboard
• Expansion card (expansion board)
–
–
–
–
Circuit board for additional devices (NIC, sound card)
Inserts into expansion slot
Device connects to computer’s main circuit or bus
Computer centrally controls device
6
Expansion Slots
7
How NICs connect
• Multiple bus types
– PCIe bus: most popular expansion board NIC
• PCIe (Peripheral Component Interconnect Express)
– 32-bit bus
– Maximum data transfer rate: 1 Gbps
– Introduced in 2004
PCIe expansion board NIC
8
Bus Types
9
How NICs connect
• Externally attached NICs
– Simple installation into a variety of slots
•
•
•
•
PCMCIA
USB
CompactFlash
FireWire
– Installing and configuring software may be required
• On-Board NICs
– Connect device directly to motherboard
– Advantages
• Saves space
• Frees expansion slots
10
How NICs connect
A USB NIC
11
How NICs connect
Motherboard with on-board NICs
12
Modular Interfaces
• Modular Interfaces
– Changes network interfaces on connectivity devices
– Hot-swappable components - Can be changed
without disrupting operations
• GBIC (Gigabit interface converter)
– May contain RJ-45 or fiber-optic cable ports
– Now mostly Obsolete
• SFPs (small form-factor pluggable)
– Provide same form factor as GBIC
• Allow more ports per inch
13
Modular Interfaces
GBIC (Gigabit interface converter)
with an RJ-45 port
SFP (small form-factor pluggable) transceiver
for use with fiber connections
14
Repeaters and Hubs
• Repeaters
– Operate in Physical OSI model layer
– No means to interpret data
– Just regenerates signal
• Hub
– Repeater with more than one output port
– Typically contains multiple data ports
• Patch cables connect printers, servers, and
workstations
– Most contain uplink port
15
Bridges
•
•
•
•
•
Device that connect two network segments
Operate at Data Link OSI model layer
Single input and single output ports
Protocol independent
Analyze incoming frames and makes decisions on
where to direct them by MAC address
• Filtering database
– Contains known MAC addresses and network
locations
• Not common anymore
16
Bridges
A bridge’s use of a filtering database
17
Switches
• Connectivity devices that subdivide a network into
segments
• Traditional switches
– Operate at Data Link OSI model layer
• Modern switches
– Can operate at Layer 3 or Layer 4 (blurs line between
switches and routers)
• Switches interpret MAC address information (just
like bridge)
• Common switch components
– Internal processor, operating system, memory, ports
18
PC connecting to a Switch
19
Switches
• Advantages
– Better performance and security
• Disadvantages
– Can be overwhelmed by heavy traffic
• Four switching methods exist
– Two basic methods discussed
1. Cut-through mode
2. Store-and-forward mode
20
Switching Methods
• Cut-through mode
– Switch reads frame’s header only
– Forwarding decision made before receiving entire
packet
• Uses frame header: first 14 bytes which contains
destination MAC address
– Cannot verify data integrity using frame check
sequence
• Cannot detect corrupt packets
21
Switching Methods
• Cut-through mode (cont’d.)
– Advantage: speed
– Disadvantage
• Data buffering (switch flooded with traffic)
– Best use
• Small workgroups needing speed
• Low number of devices
22
Switching Methods
• Store-and-forward mode
– Switch reads entire data frame into memory
– Checks for accuracy before transmitting information
(frame check)
– Transmit data more accurately than cut-through mode
– Slower than cut-through mode because reads entire
frame
– Best uses
• Larger LAN environments
– Can transfer data between segments running different
transmission speeds
23
VLANs
• VLANs (virtual local area networks)
– Concept of partitioning a physical network
– Logically separate networks not physical
• Groups ports into broadcast domain
• Broadcast domain
– All nodes can reached each other by a broadcast
message
• Collision domain
– Data packets can collide with one another when being
sent on a shared medium
24
A simple VLAN design
25
VLANs
• Advantage of VLANs
– Flexible
• Ports from multiple switches or segments grouped
• Any end node type (PCs, printers) can belong to VLAN
– Reasons for using VLAN
•
•
•
•
•
Separating user groups
Isolating connections
Identifying priority device groups
Grouping legacy protocol devices
Separating large network into smaller subnets
26
VLANs
• Switch typically preconfigured
– One default VLAN
– Cannot be deleted or renamed
• Create additional VLANs
– Indicate to which VLAN each port belongs
• Maintain VLAN using switch software
• Potential problem
– Cutting off group from rest of network
27
Show vlan command
28
Trunking
• Trunking
– Switch’s interface carries traffic of multiple VLANs
• Trunk
– Single physical connection between
• VLAN data separation (tag)
– Frame contains VLAN identifier in header
29
VLANs and Trunking
Trunk for multiple VLANs
30
VLAN and Trunking
• VLAN and Trunking
31
STP (Spanning Tree Protocol)
• IEEE standard 802.1D
• Operates in Data Link layer
• Prevents traffic loops
– Calculating paths to avoid potential loops
– Artificially blocks links completing loop
• Three steps
– Select root bridge based on Bridge ID (lowest mac
number)
– Examine possible paths between network bridge and
root bridge
– Disables links not part of shortest path
32
Enterprise-wide switched network
33
STP-selected paths on a switched network
34
STP (Spanning Tree Protocol)
• History
– Introduced in 1980s
• Original STP too slow responding to changes
– RSTP (Rapid Spanning Tree Protocol)
• Newer version
• IEEE’s 802.1w standard
• Cisco and Extreme Networks
– Have proprietary versions
• No enabling or configuration needed
– Included in switch operating software
35
Content and Multilayer Switches
• Blurring lines between switches and routers
• Layer 3 switch (routing switch) - Interprets Layer 3
data
• Layer 4 switch - Interprets Layer 4 data
• Content switch (application switch)
– Interprets Layer 4 through Layer 7 data
• Advantages of interpreting higher layers
– Advanced filtering
– Keeping statistics
– Security functions
• Disadvantage – Cost, standards
36
Routers
• Multiport connectivity device
– Integrates LANs and WANs
• Operate at Network layer (Layer 3)
– Directs data between network nodes and from one
segment or network to another
– Uses logical addressing, Protocol dependent
• Slower than switches and bridges
– Need to interpret Layers 3 and higher information
• Traditional stand-alone LAN routers
– Being replaced by Layer 3 routing switches
37
Router
Characteristics and Functions
• Intelligence
– Determine shortest, fastest path between two nodes
– Connects dissimilar network types
• Large LANs and WANs
– Routers indispensable
• Router components
– Internal processor, operating system, memory, input
and output jacks, management control interface
38
Router
Characteristics and Functions
• Multiprotocol routers
– Multiple slots
– Accommodate multiple network interfaces
• Inexpensive routers
– Home, small office use
• Router capabilities
– Interpret Layer 3 addressing
– Determine best data path
– Reroute traffic
39
Routers
40
Router Types and Terms
• 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 (database)
– Maintain information where hosts are and how to
reach them
• Static routing
– Router configured to use specific path between nodes
• Dynamic routing
– Automatically calculates best path between nodes 41
The placement of routers on a LAN
42
Routing Protocols
• How to decide on best path
– Path is decided by routing protocol
• Routing metric factors
–
–
–
–
–
–
–
Number of hops
Throughput on potential path - Transmission speed
Delay on a potential path - Current network activity
Load (traffic)
Maximum transmission unit (MTU)
Reliability of potential path - Unavailable link
Cost (assigned by administrator)
43
Routing Protocols
• Router Convergence Time (con’t)
– The time the router takes to recognize best path after
change or network outage event
44
Routing Protocols
Summary of common routing protocols
45
Routing Protocols
• Distance-vector type routing protocols - RIP, RIPv2,
BGP
– Determine best route based on distance to
destination
– Factors
• Hops, latency, network traffic conditions
• RIP (Routing Information Protocol)
– Only factor is number of hops between nodes
• Limits 15 hops
– Type of IGP (Interior Gateway Protocol)
• Can only route within internal network
– Slower and less secure than other routing protocols
46
Routing Protocols
• RIPv2 (Routing Information Protocol Version 2)
– Generates less broadcast traffic, more secure than
RIP
– Cannot exceed 15 hops
– Less commonly used
• BGP (Border Gateway Protocol)
–
–
–
–
–
Type of EGP (Exterior Gateway Protocol)
Most complex (choice for Internet traffic)
Communicates using BGP-specific messages
Many factors determine best paths
Configurable to follow policies
47
Routing Protocols
• Link-state type routing protocol – OSPF and IS-IS
– 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 determining best paths
Each OSPF router
• Maintains database containing other routers’ links
48
Routing Protocols
• IS-IS (Intermediate System to Intermediate System)
– Codified by ISO
– Interior routers only!
– Supports two Layer 3 protocols
• IP
• ISO-specific protocol
– Much less common than OSPF
49
Routing Protocols
• Hybrid type routing protocol - EIGRP
– Link-state and distance-vector characteristics
– EIGRP (Enhanced Interior Gateway Routing Protocol)
• Most popular
• Cisco network routers only!
– EIGRP benefits
•
•
•
•
Fast convergence time, low network overhead
Easier to configure and less CPU-intensive than OSPF
Supports multiple protocols
Accommodates very large, heterogeneous networks
50
Gateways and Other Multifunction
Devices
• Gateway
– Combination of networking hardware and software
– Connects two systems that use different formatting,
communications protocols, architecture
– They repackages information
– Can reside on servers, microcomputers, connectivity
devices, mainframes
• Popular gateways
– Firewall, E-mail gateway, Internet gateway, voice/data
gateway, LAN gateway
51
Summary
•
•
•
•
•
Network adapter types vary (NIC)
Repeaters - Regenerate digital signal
Hubs
Bridges can interpret the data they retransmit
Switches subdivide a network
– Create VLANs
– Trunking
• Routers
– Various routing protocols
• Gateways
52
End of Chapter 6
Questions
53