Module 4:Designing Routing and

Switching Requirements

Connectivity Requirements

Branch OfficeBranch Office

Corporate HeadquartersCorporate Headquarters

Web Server

Internet

Server

LAN

LAN

Remote User

Remote User

VPN

Wireless User

•Locally

•Remotely

•Across the Internet

Evaluate how users connect

Types of Network Devices

Device OSI layer Definition

Hub• Physical

(layer 1)

• Extends the network by retransmitting the signal

• Does not process the data

Switch• Data-link

(layer 2)

• Forwards frames according to the destination MAC address

• Supports simultaneous conversations without collisions

Router• Network

(layer 3)• Used to link WANs and dissimilar LANs• Sends packets based on logical addressing

Layer 3 switch

• Network (layers 2 and 3)

• Is a limited-purpose hardware-based IP router with bridging capabilities

• Also performs layer 2 switching

Reasons for Using Routers

Use routers to:

• Isolate networks from each other• Provide a start for a secure network

implementation

Traditional uses of routers

• Connecting WANs• Segmenting LANs

Internet Security and Acceleration for Internet Connectivity

131.107.0.9

IntranetIntranet

10.10.10.810.10.10.8

ISA ServerISA Server

10.10.10.0 maps to 131.107.0.9

10.10.10.0 maps to 131.107.0.9

10.10.10.710.10.10.7

10.10.10.910.10.10.9

10.10.10.1010.10.10.10

10.10.10.810.10.10.8

131.107.0.9

ISA has additional features over NAT:

• Application traffic monitoring

• Internet content caching

• User-based control

Strategies for Designing Firewalls

Bastion hostBastion host

Web Server

LAN

Multi-homed firewallMulti-homed firewall

LANWeb Server

Back-to-back firewallBack-to-back firewall

Web Server

LAN

Internet

Strategies for Designing Extranet

Option Description

VPN • Encrypted communication over the Internet

Dial-up • Computer communication over phone lines

Secure Web server

• Authenticated access to a Web server

RPC over HTTP• RPC communication tunnelled in HTTP for an

application

Terminal services

• Remote access to an application

ADFS• Active Directory authentication for Web

applications

Determining Connection Methods

Connection method Use when:

Leased lines• Security is important• Speed and reliability are required• No budget constraints

Tunneling• Security is important• No modem infrastructure

Demand-dial -on demand

• Limited traffic • Per-instance fee pricing structure

Demand-dial -persistent

• Ample traffic• Flat fee pricing structure

Selecting a Site-to-Site VPN Tunnel

VPN tunnel type Criteria

VPN with PPTP tunnel is used if:

• All routers support PPTP passthrough• User-based authentication is sufficient• Support for non-IP protocols is required

VPN with L2TP/IPSec tunnel is used if:

• All routers support passthrough of IPSec• Computer-based authentication is required• Support for non-IP protocols is required

VPN with IPSec in tunnel mode is used if:

• All routers support passthrough of IPSec• Only computer-based authentication is

required• Support for only TCP/IP is required

Factors Affecting Network Performance

Factors affecting network performance

• Bandwidth

• Latency

• Throughput

• Capacity

• Wire speed

• Utilization

• Jitter

• Jabber

• Bottleneck

• Collisions

• Efficiency

• Frame rate

Network Upgrade Considerations

When determining how to upgrade a network, consider:

• Current utilization rates at various times of day

• Appropriate target utilization rates

• Flow of traffic through the network

• Future growth

• Potential repercussions

Calculating Actual Data Throughput

Actual data throughput formula

• ADT = net utilization * efficiency rating * wire speed

• Net utilization = (utilization - collisions)

• Efficiency rating based on frame size

• Actual Data Throughput (ADT) shows you how much usable data is actually being carried on the network

• Adding nodes and header information affects throughput

• You should measure throughput after data transmission

What Is Quality of Service?

Quality of Service (QoS):

• Prioritizes network traffic for network routing by adding a DSCP value

• Uses throttling to limit bandwidth usage on a host

Can be based on:

• Sending application

• Source or destination IPv4 or IPv6 addresses

• Protocol (TCP or UDP)

• Source or destination ports

What Is a QOS Policy?

A QoS policy:

• Is defined as part of a Group Policy

• Can be applied to users or computers

• Can include specific IPv4 or IPv6 addresses or networks to apply to

• Lets you define a DSCP value for network traffic

• Lets you define a throttle rate for network traffic