Download Connecting the Switch Block

Overview of a Campus
Network
© 1999, Cisco Systems, Inc.
1-1
Objectives
Upon completion of this chapter, you will
be able to perform the following tasks:
• Discuss the forces that impact the design of campus
networks
• Describe Layer 2, 3, 4, and Multilayer Switching
functions
• Identify the hierarchical layer solution for a given
network requirement
• Discuss the elements of the building block approach
• Identify the correct Cisco product solution, given a
set of customer requirements
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-2
Campus Network Overview
In this chapter, we discuss the following
topics:
• Campus network overview
• The emerging campus model
• The hierarchical model
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-3
Campus Network Overview (cont.)
The following section discusses:
Campus Network Overview
• Traditional Campus Networks
• Issues and Solutions
• Traffic Patterns
The Emerging Campus Model
The Hierarchical Model
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-4
Characteristics of a Campus
Network
Token
Ring
Token
Ring
• Fixed geographic area
• Owned and administered by organization
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-5
Traditional Campus Networks
Broadcast Domain
Collision Domain 2
Collision Domain 1
• Bridges terminate collision domains
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-6
Performance Issues
I need to know
the MAC
address for
Server A
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
ARP
Server A
• Multicast, broadcast, and unknown destination
events become global events
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-7
Broadcast Issues
Server A
• Broadcasts can consume all available bandwidth
• Each device must decode the broadcast frame
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-8
Solution: Localizing Traffic
10.1.1.0
10.1.2.0
10.1.3.0
• LAN broadcasts terminate at the router interface
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-9
Solution: Localizing Traffic
(Cont.)
VLAN1
VLAN2
VLAN3
• VLANs contain broadcast traffic and separate traffic flows
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-10
Current Campus Networks
VLAN1
VLAN2
VLAN3
VLAN5
VLAN6
VLAN7
VLAN8
VLAN9
VLAN10
• Layer 3 devices interconnect LAN segments while still
containing broadcast domains
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-11
Understanding Traffic Patterns
• Successful network implementations consider traffic patterns
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-12
The 80/20 Rule
80+%
Local Traffic
VLAN1
VLAN2
80+%
Local Traffic
20%
Remote Traffic
VLAN3
80+%
Local Traffic
• 80 percent of the traffic is local; 20 percent is remote
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-13
The New 20/80 Rule
20%
Local Traffic
VLAN1
VLAN2
20%
Local Traffic
80+%
Remote Traffic
VLAN3
20%
Local Traffic
• 20 percent of the traffic is local; 80 percent is remote
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-14
Emerging Traffic Patterns
VLAN1
VLAN2
VLAN4
VLAN3
• The 20/80 rule challenges VLAN implementation
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-15
Campus Network Overview
This section discusses the following:
• Campus Network Overview
• The Emerging Campus Model
–Customer requirements
–Emerging campus structure
–Switching technologies
• The Hierarchical Model
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-16
Customer Network Requirements
• Fast convergence
• Deterministic paths
• Deterministic failover
• Scalable size and
throughput
• Centralize applications
• The new 80/20 rule
• Multiprotocol support
• Multicasting
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-17
Emerging Campus Structure
Remote Services
80% NonLocal Traffic
Enterprise Services
Local Services
• Traffic patterns dictate the placement of services
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-18
Local Services
• Devices connected by
switches
• Traffic within the same
subnet/VLAN
• Traffic does not cross the
backbone
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-19
Remote Services
• Devices connected by routers
• Traffic crosses subnet/VLAN
• Segregated by Layer 3
• Traffic may/may not cross the
backbone
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-20
Enterprise Services
• Common to all users
• Traffic crosses subnet/VLAN
• Traffic crosses the backbone
• Segregated by Layer 3
• May be grouped by Layer 2
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-21
Basic Layer Terminology
Application
Presentation
Session
Segments
Transport Layer
Logical
Ports
Packets
Network Layer
Routers
Frames
Data Link
Switches/
Bridges
Physical
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-22
Layer 2 Switching
• Hardware-based bridging
• Wire-speed performance
• High-speed scalability
• Low latency
• MAC address
• Low cost
Data Link
© 1999, Cisco Systems, Inc.
www.cisco.com
7
6
5
4
3
2
1
BCMSN—2-23
Impact of Layer 2 Switching
• Layer 2 switched networks have the same
characteristics as bridged networks
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-24
Benefits of Routing
• Broadcast control
• Multicast control
• Optimal path determination
• Traffic management
• Logical addressing
E0
10.1.1.1
• Layer 3 security
E1
10.2.2.2
10.1.1.1
© 1999, Cisco Systems, Inc.
E0
E1
www.cisco.com
10.2.2.2
BCMSN—2-25
Layer 3 Switching
• Hardware-based packet
forwarding
• High-performance
packet switching
• High-speed
scalability
• Low latency
Network Layer
• Lower per-port cost
• Flow accounting
• Security
7
6
5
4
3
2
1
• QoS
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-26
Layer 4 Switching
• Based on Layer 3
• Based on applicationrelated information
Transport Layer
© 1999, Cisco Systems, Inc.
www.cisco.com
7
6
5
4
3
2
1
BCMSN—2-27
Multilayer Switching
• Combines functionality of:
– Layer 2 switching
– Layer 3 switching
– Layer 4 switching
• High-speed scalability
Transport Layer
• Low latency
Network Layer
Data Link
© 1999, Cisco Systems, Inc.
www.cisco.com
7
6
5
4
3
2
1
BCMSN—2-28
Campus Network Overview
The following section discusses:
• Campus Network Overview
• The Emerging Campus Model
• The Hierarchical Model
–Access, Distribution, and Core Layers
–The building block approach
–Campus network availability example
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-29
The Hierarchical Model
Access Layer
Distribution Layer
Core Layer
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-30
Access Layer
• Entry point to the network
• Shared bandwidth
• Layer 2 services
–Filtering
–VLAN membership
Access Layer
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-31
Distribution Layer
• Access aggregation point
• Workgroup services access
• Broadcast domains definition
• InterVLAN routing
• Media translation
• Security
Distribution Layer
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-32
The Core Layer
• Fast transport
• No Layer 3 processing
Core Layer
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-33
The Building Block Approach
Building A
Building B
Building C
Switch
Block
Mainframe Block
WAN Block
Core
Block
Token
Ring
Server
Block
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-34
Layer 3 Backbone Scaling
• Fast convergence
• Load balancing
• No peering problems
• Performance/cost issues
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-35
Chapter 10
Controlling Campus
Connecting the Switch Block
Device Access
© 1999, Cisco Systems, Inc.
3-36
1-36
Objectives
Upon completion of this chapter, you will
be able to perform the following tasks:
• Provide physical links between devices
• Configure connectivity to the access layer using
Ethernet
• Configure high-speed access to the distribution
layer using Fast Ethernet
• Provide an secondary high-speed path to a backup
distribution switch using Fast Ethernet
• Enable inter-block communications through links
to the core.
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-37
Connecting the Switch Block
In this chapter, we discuss the following
topics:
• Cable media types
• Cabling switch block devices
• Configuring connectivity within
the switch block
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-38
Connecting the Switch Block
(cont.)
In this section we discuss the following topics:
• Cable media types
–Ethernet
–Fast Ethernet
–Gigabit Ethernet
• Cabling switch block devices
• Configuring connectivity within
the switch block
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-39
Problem: Need for More
Bandwidth
Bandwidth requirement is impacted by the number of users
and types of applications
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-40
Solution: Ethernet 10BaseT in
the Switch Block
Ethernet 10BaseT
Ethernet 10BaseT
10-Mbps LAN switching is integrated to the desktop,
providing dedicated bandwidth and virtual LAN
services to the end stations.
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-41
Solution: Fast Ethernet in the
Switch Block
100 Mbps
100
Mbps
100
Mbps
• Enhances client/server performance across the enterprise
• Connect directly to Fast Ethernet interfaces on LAN switches
which aggregate traffic from 10-Mbps segments
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-42
Increasing FE Performance
with Full Duplex
100 Mbps
200 Mbps
100 Mbps
In full-duplex mode, 100 Mbps is available in
each direction
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-43
Increasing FE Performance
with Autonegotiation
10 Mbps
I am sending data
at 100 Mbps
I am sending data
at 10 Mbps
100 Mbps
Allows devices at each end of a network link to
automatically exchange information about the
link capabilities
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-44
Solution: Gigabit Ethernet in
the Switch Block
1000 Mbps
1000
Mbps
1000
Mbps
• Enhances client/server performance across the enterprise
• Connects directly to Gbps interfaces on LAN switches which
aggregate traffic from 10- or 100-Mbps segments
• Connects distribution-layer switches in each building with a
central campus core
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-45
Connecting the Switch Block
In this section we discuss the following topics:
• Cable media types
• Cabling switch block devices
• Configuring connectivity within the switch block
– Limiting switch access
– Uniquely defining switching
– Configuring switch remote accessibility
– Identifying switch ports
– Defining link speed
– Maximizing data transmission
– Verifying connectivity
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-46
Limiting Access to Devices
Passwords are used to limit access to the switch
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-47
Uniquely Identifying a Device
Hello, My Name Is:
ASW44
Catalyst 1912
Switch(config)#hostname ASW44
ASW44(config)#
Hello, My Name Is:
Catalyst 5000
DSW145
Switch(enable)prompt DSW145
DSW145(enable)
Hello, My Name Is:
Catalyst 6500
CORE1
Switch(enable)#prompt CORE1
CORE1(enable)
The host or prompt name uniquely identifies each
device at the command-line interface
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-48
Configuring Switch Remote
Accessibility
176.16.1.21
176.16.1.3
176.16.1.1
176.16.1.22
176.16.1.23
176.16.1.33
176.16.1.32
176.16.1.31
Management VLAN = 176.16.1.0
An IP address associates a switch with a
management VLAN
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-49
Maximizing Data Transmission
Full duplex is the simultaneous action of transmitting
and receiving data by two devices
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-50
Verifying Connectivity
Switch#ping 172.16.1.47
Sending 5, 100-Byte ICMP Echos to 172.16.1.47,
Timeout Is 2 Seconds:
172.16.1.47
!!!!!
Success Rate Is 100 Percent (5/5),
Round-Trip min/avg/max 0/4/10/ ms
The ping command sends a specified number of ICMP
echo requests and measures the time the destination
device takes to respond to each request
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-51
Understanding
Virtual LANs
© 1999, Cisco Systems, Inc.
1-52
Agenda
What Is a VLAN?
How Does it Work?
VLAN Technologies
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-53
Constraints of Shared LANs
• Users are physically bound
• Subnets are tied to hubs
• Users are grouped by
location
• No security on segment
• Addressing is constrained
• Moves require address
changes
• Router ports are expensive
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-54
Virtual LANs
VLAN 1
VLAN 2
VLAN 3
Server Farm
• One broadcast domain
within a switch
• VLANs help manage
broadcast domain
• Can be defined on
port groups, users, or
protocols
• LAN switches and
network management
software provide a
mechanism to create
VLANs
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-55
Remove the Physical
Boundaries
Engineering
Marketing
Acctg.
Floor 3
Floor 2
Floor 1
Group users by department, team, or application
Routers provide communication between VLANs
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-56
VLAN Benefits
Reduced administrative costs
• Simplify moves, adds, and changes
Efficient bandwidth utilization
• Better control of broadcasts
Improved network security
• Separate VLAN group for high-security users
• Relocate servers into secured locations
Scalability and performance
• Microsegment with scalability
• Distribute traffic load
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-57
Membership by Port
Maximizes Forwarding Performance
VLAN 3
VLAN 1
© 1999, Cisco Systems, Inc.
VLAN 2
Users assigned by port
association
Requires no lookup if
done in ASICs
Easily administered via GUIs
Maximizes security between
VLANs
Packets do not “leak” into
other domains
Easily controlled across network
www.cisco.com
BCMSN—2-58
Communicating Between VLANs
Two Physical Topology Approaches
Logical
Communication
VLANs 1, 2, 3
Cisco Internetworking
Software
Physical Link
per VLAN
VLAN 3
VLAN 2
VLAN 1
© 1999, Cisco Systems, Inc.
Layer 3 links
VLANs together
Adds additional security
and management
Logical links conserve
physical ports
Multimode, depending
on protocol
Controls access by VLAN
Up to 255 VLANs per router
www.cisco.com
BCMSN—2-59
VLAN Technologies
© 1999, Cisco Systems, Inc.
www.cisco.com
© 1999, Cisco Systems, Inc.
1-60
Spanning Tree
© 1999, Cisco Systems, Inc.
1-61
What is Spanning Tree
Spanning Tree defined in
IEEE 802.1D specification
I Do Not know where
“B” is - So I’ll
send it
out all ports
B
A
Send a message
to “B”
© 1999, Cisco Systems, Inc.
I Do Not know where
“B” is - So I’ll send it
out all ports
www.cisco.com
BCMSN—2-62
What is Spanning Tree
Spanning Tree
Creates a loop free
topology in Layer 2
Switch network
B
A
Send a message
to “B”
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-63
Switched LAN STP States
Listening
Learning
P1
P2
P3
VLAN1
Forwarding
Blocking
P4
Ethernet
Hub
Disabled—port STP is not enabled
Listening—port is in pre-forwarding state 1
Learning—port is in pre-forwarding state 2
Forwarding—allows for output packets
Blocking—port is in non-forwarding state because of a loop detection
Cisco special Port-Fast mode
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-64
Per VLAN Spanning Tree
PVST+
Purple Link
Forwarding
for ALL VLAN’s
No
PVST+
Red Link
Blocked
VLAN Trunk
Purple Link
Forwarding for
odd VLAN’s
With
PVST+ it
maximizes use
of all links
Green Link
Forwarding
for even VLAN’s
VLAN Trunk
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-65
Port Fast, Uplink Fast and
Backbone Fast
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-66
Uplink and Backbone Fast
Uplink Fast
Switch 1
Switch 2
Switch 1
Un-Blocked
Blocked
Backbone Fast
Switch 2
Un-Blocked
Blocked
Direct Link Fails
In-Direct Link Fails
Uplink Fast places
blocked link into
forwarding state
Backbone Fast places
blocked link into
forwarding state
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-67
Configuring HSRP for
Fault Tolerant Routing
© 1999, Cisco Systems, Inc.
1-68
Solution: Hot Standby Routing
Protocol
HSRP
Group
Core
• HSRP defines a set of routers working together to represent one
virtual fault-tolerant router
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-69
Solution: Hot Standby Routing
Protocol (cont.)
Active
Router
Core
• Packets are still routed even when the active router fails
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-70
HSRP Group Members
HSRP Group
Standby
Router
Virtual Router
Active
Router
• HSRP standby groups consist of multiple routers
performing specific roles
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-71
Chapter 10
Controlling Campus
Multicast Overview
Device Access
© 1999, Cisco Systems, Inc.
10-72
1-72
Multicast Overview
In this chapter, we discuss the following
topics:
• Multicast overview
• Addressing in a multicast
environment
• Managing multicast traffic in a
campus network
• Routing multicast traffic
• Multicast routing protocols
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-73
Multicast Overview
In this section, we discuss the following
topics:
• Multicast Overview
– Unicast Traffic
– Broadcast Traffic
– Multicast Traffic
– IP Multicast Characteristics
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus
Network
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-74
Unicast Traffic
Video
Server
Receiver
Receiver
Receiver
Not A
Receiver
• Unicast applications send one copy of each packet to every client
unicast address
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-75
Unicast Traffic (cont.)
1.5 Mb x 3 = 4.5 Mb
Video
Server
1.5 Mb x 2 = 3 Mb
1.5 Mb x 1 = 1.5 Mb
1.5 Mb x 1 = 1.5 Mb
1.5 Mb x 1 = 1.5 Mb
Receiver
© 1999, Cisco Systems, Inc.
1.5 Mb x 1 = 1.5 Mb
Receiver
Receiver
www.cisco.com
Not A
Receiver
BCMSN—2-76
Unicast Traffic (cont.)
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150
Mb
Video
Server
1.5 Mb x 100 = 150 Mb
1.5 Mb x 100 = 150 Mb
...
Receiver 1
© 1999, Cisco Systems, Inc.
Receiver 100
www.cisco.com
BCMSN—2-77
Broadcast Traffic
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
I don’t want to receive
this video stream, but
my CPU still needs to
process that 1.5 MB
of data!
1.5 Mb
Not A
Receiver
• Hosts not using a multimedia application must still process the
broadcast traffic
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-78
Multicast Traffic
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
Not A
Receiver
• A multicast server sends out a single data stream to multiple clients
using a special broadcast address
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-79
IP Multicast Characteristics
• Transmits to a host group
• Delivers with “best effort”
reliability
• Supports dynamic membership
• Supports diverse numbers and
locations
• Supports membership in more
than one group
• Supports multiple streams host
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-80
Multicast Overview
In this section, we discuss the following
topics:
• Multicast Overview
• Addressing in a Multicast Environment
– IP Multicasting Address Structure
– Mapping MAC addresses to IP
Multicast Addresses
• Managing Multicast Traffic in a Campus
Network
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-81
Group Membership
Are there any
members for
Group XYZ?
Host D
Host A
I’m a member
so I will
respond.
Host B
I’m not a
member so I
won’t respond.
Host C
I’m a member
so I will
respond.
I’m a member
so I will
respond.
• Multicast uses query and report messages to
establish and maintain group membership
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-82
IGMPv2—Joining a Group
172.16.41.1
H1
172.16.41.2
224.1.1.1
H2
172.16.41.3
H3
Report
172.16.41.141
RTR141
• Joining member sends report to 224.1.1.1
immediately upon joining (same as IGMPv1)
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-83
IGMPv2—Joining a Group
(cont.)
172.16.41.1
H1
172.16.41.2
172.16.41.3
H2
H3
172.16.41.141
E0
RTR141
RTR141>show ip igmp group
IGMP Connected Group Membership
Group Address
Interface
Uptime
224.1.1.1
Ethernet0
6d17h
© 1999, Cisco Systems, Inc.
www.cisco.com
Expires
00:02:31
Last Reporter
172.16.41.2
BCMSN—2-84
Multicast Overview
In this section, we discuss the following
topics:
• Multicast Overview
• Addressing in a Multicast Environment
• Managing Multicast Traffic in a Campus
Network Routing
– GCMP
• Routing Multicast Traffic
• Multicast Routing Protocols
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-85
Layer 2 Multicast
1.5 Mb
Video
Server
1.5 Mb
1.5 Mb
Receiver
© 1999, Cisco Systems, Inc.
1.5 Mb
Receiver
1.5 Mb
1.5 Mb
Receiver
www.cisco.com
I don’t want to receive
this video stream, but
my CPU still needs to
process that 1.5 MB
of data!
1.5 Mb
Not A
Receiver
BCMSN—2-86
CGMP
0000.0c12.3456
would like to
join multicast
group XYZ.
0000.0c12.3456
• CGMP is a Cisco-developed protocol
• CGMP allows Catalyst switches to learn about the
existence of multicast clients from Cisco routers
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-87
CGMP (cont.)
I can reach device
0000.0c12.3456
out of Port 1. I will
add 234.10.8.5
to my switch
forwarding table.
Device
0000.0c12.3456
wants to join
Group 234.10.8.5
I have no
knowledge of
device
0000.0c12.3456
0000.0c12.3456
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-88
Understanding
Quality of Service
© 1999, Cisco Systems, Inc.
1-89
Agenda
What Is QoS?
QoS Building Blocks
QoS in Action
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-90
What Is Quality of Service
(QoS)?
The ability of the network to
provide better or “special” service
to users/applications.
Data, Video, Voice
Consistent Predictable
Performance
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-91
What Is Quality of Service
(QoS)?
Desktop
Conferencing,
Distance
Learning
• Classification
Mission-Critical
Applications
• Policing
E-Mail
• Shaping
File
Transfer
• Congestion
avoidance
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-92
What Is Driving the Need
for QoS?
Mission-Critical Apps
Voice
Video
None
Other
0
20
40
60
80
100
Source: Forrester, August 1998, Fortune 1000
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-93
What Are Mission-Critical
Applications?
• Enterprise Resource
Planning (ERP) applications
– Order entry
– Finance
– Manufacturing
– Human resources
– Supply-chain management
– Sales-force automation
• What else is mission critical?
– SNA applications
– Selected physical ports
– Selected hosts/clients
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-94
QoS Benefits
Control network resources
Improve cost efficiency
• Increase WAN efficiency
• Minimize administrative overhead
Create a “business-enabling” technology
foundation
Combine mission-critical,
voice, and video applications
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-95
LAN QoS Requirements
Are Emerging
QoS is beneficial when there is link congestion
and for buffer management
• Points of substantial speed mismatch and
points of aggregation are congestion
candidates
• Prerequisite to multimedia deployment is
the need to prioritize mission-critical
applications
• Buffering reduces loss but delay-sensitive
application could be negatively impacted
– Such as Ethernet transmit queue:
164K at 10 Mbps --> 128-ms delay
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-96
QoS Example
Sales
Manager
Remote
Campus
Product
Manager
Public
Frame Relay
Campus
Backbone
Training
Servers
Network Resources
Who
ERP
Quality of Service
When
High
365 x 24 x 7
Video
< 100 KB
M–F, 9–5
VoIP
< 150 ms
M–F, 9–5
© 1999, Cisco Systems, Inc.
www.cisco.com
Order Entry,
Finance,
Manufacturing
BCMSN—2-97
QoS Building Blocks
© 1999, Cisco Systems, Inc.
www.cisco.com
© 1999, Cisco Systems, Inc.
1-98
Quality of Service Building
Blocks
Policing
Classification
• IP Precedence
• Committed Access Rate (CAR)
• Diff-Serv Code Point (DSCP)
• IP-to-ATM Class of Service
• Network-Based Application
Recognition (NBAR)
• Resource Reservation Protocol
(RSVP)
• Committed Access Rate (CAR)
• Class-Based Weighted Fair Queuing
(CB WFQ)
• Weighted Fair Queuing (WFQ)
Shaping
• Generic Traffic Shaping (GTS)
• Distributed Traffic Shaping (DTS)
• Frame Relay Traffic Shaping (FRTS)
Congestion Avoidance
• Weighted Random Early Detection
(WRED)
• Flow-Based WRED (Flow RED)
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-99
Congestion Management—
Fancy Queuing
Weighted Fair Queuing
• Automatically allocates bandwidth “fairly”
Session 1Session 2Session 3 Session 4
SQLnet
SNA
FTP
HTTP
Other queuing options include FIFO,
priority queuing, and custom queuing
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-100
Random Early Detection (RED)
RED reduces long-term
average queue
Packet drops
are randomized throughout
queue depth
Drop rate is
increased as queue depth
is increased
© 1999, Cisco Systems, Inc.
www.cisco.com
Transmit
Buffer
Queue
BCMSN—2-101
Weighted RED
WRED addresses:
• In the event packets
need to be dropped,
what class of packets
should
be dropped
Queue
Packets classified
as blue start dropping
at a 50% queue depth.
Drop rate is increased as
queue depth is increased.
© 1999, Cisco Systems, Inc.
www.cisco.com
Packets classified
as gold are dropped
at 90% queue depth.
BCMSN—2-102
Example: No Quality of
Service
Jittery
Video
Server
Client
• No quality of service
• Resources consumed
by other applications
• Unmanaged traffic
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-104
Example: With Quality of
Service—RSVP
This app. needs
1-Mbps BW and
200-ms delay
Reserve
1-Mbps BW
on this line
Reserve
1-Mbps BW
on this line
Reserve
1-Mbps BW
on this line
Reserve
1-Mbps BW
on this line
I need 1-Mbps
BW and
200- ms delay
Video
Server
Clear!
Client
• Reserves bandwidth end-to-end
• Guarantees delay-sensitive applications
• Must be supported on clients, servers,
and routers
© 1999, Cisco Systems, Inc.
www.cisco.com
BCMSN—2-105
End-to-End QoS
RSVP For
End-End Reservation
FR or ATM
Services
Traffic Shaping
Traffic Shaping
Intranet
802.1p:
Traffic Filtering
for Switching
Leased Line
Policy Routing
Smart
Queuing
Mainframe
Remote Site
Campus Network
© 1999, Cisco Systems, Inc.
Link Fragmentation
and Interleaving
www.cisco.com
BCMSN—2-106
Where to Apply QoS Features
Access
Switch
Fast
Ethernet
QoS Ingress
• Classification
© 1999, Cisco Systems, Inc.
Aggregation
Router
Fast
Ethernet
Backbone
Router
QoS WAN Edge
• Admission
Control
Classification
• Congestion
Avoidance
• Congestion
Management
www.cisco.com
QoS
Core
OC-3
QoS Core
• Congestion
Avoidance
• Congestion
Management
BCMSN—2-107
QoS in Action
© 1999, Cisco Systems, Inc.
www.cisco.com
© 1999, Cisco Systems, Inc.
1-108
Example 1: Prioritization
of IP Telephony
Set Telephony = High TOS
=5
Set Game = Low
TOS = 2
Si
For TOS = 5
Threshold = 4
High Priority Queue
(70% Transmit Ratio,
Low Delay)
For TOS = 2
Threshold = 2
Low Priority Queue
(30% Transmit Ratio,
High Delay)
© 1999, Cisco Systems, Inc.
Si
www.cisco.com
BCMSN—2-109
Example 2: ERP Application
Untrusted
Client
QOS Ingress
QOS Core
Reclassify
Schedule
TCP, L4-Port = 1521
According
Set TOS = 5
to TOS = 5
Drop Threshold=Low
SQL Client
Access
Switch
Backbone
Switch
Database 10.1.2.1
Server Farm
Switch
Database 10.1.2.2
SQL Listener
Server Farm
© 1999, Cisco Systems, Inc.
Schedule
According to
TOS = 5
Reclassify IF:
L4-Port = 1521
IP-SA/DA = 10.1.2.1
IP-SA/DA = 10.1.2.2
Set TOS = 5
QOS Core
QOS Ingress
www.cisco.com
Client
BCMSN—2-110
Presentation_ID
© 1999, Cisco Systems, Inc.
www.cisco.com
111