Transcript Remote Access Server

Module 9: Remote User
Connectivity
Overview

Introducing Routing and Remote Access

Designing a Functional Remote Access Solution

Securing a Remote Access Solution

Enhancing a Remote Access Design for Availability

Optimizing a Remote Access Design for Performance

An organization might allow dial-up clients and remote
office locations to access its private network resources.
The remote access features of Routing and Remote
Access in Microsoft® Windows® 2000 provide secure,
dial-up access to a network for remote access clients.
The remote access clients connect remotely by using
various protocols and connection types.
At the end of this module, you will be able to:

Recognize Routing and Remote Access as a solution for
remote access.

Identify the design decisions that influence a functional
remote access solution.

Select appropriate strategies to secure remote access
connections.

Select appropriate strategies to enhance remote access
availability.

Select appropriate strategies to improve remote access
performance.
Introducing Routing and Remote Access

Design Decisions for a Remote Access Solution

VPN with Remote Access Solutions

Routing and Remote Access Features

Integration Benefits

Routing and Remote Access enables remote access
clients to access corporate networks as if they were
directly connected to the corporate network. The remote
access clients connect to the network by using dial-up
communication links.
To design a remote access solution, you need to:

Identify the decisions influencing a remote access
solution.

Describe the architectural elements of a virtual private
network (VPN) in a remote access networking strategy.

Identify the features offered by Routing and Remote
Access so that you can apply them successfully in the
network design.

Identify the benefits of integrating Routing and Remote
Access with other Windows 2000 services.
Design Decisions for a Remote Access Solution
Adapter or
Modem
Remote
Access
Client
Public
Network
Adapter or
Modem
Remote
Access
Server
Provider Network
PSTN
X.25
ISDN
Intranet

Number of Dial-Up Clients?

Local or Network-Wide Resources?

Connection Technologies?

Client Authentication, Security, and Encryption?

Client Connection Protocols?

Routing and Remote Access supports dial-up
connections for remote users connecting to a private
network. Users can access resources on the remote
access server or on attached networks, provided they
meet the network security requirements defined for the
network design.

Providing a Routing and Remote Access solution can
reduce the dependence on service infrastructures (such
as Internet service providers (ISPs)), and the
performance variability of the Internet.
In designing a Routing and Remote Access solution, you need to
consider the:

Maximum number of simultaneous user connections required.

Types of resources that the clients would require to access (local,
remote, or both).

Connection technologies and throughput requirements. For
example, connections that use modems over Public Switched
Telephone Network (PSTN), Integrated Services Digital Network
(ISDN), or X.25.

Client authentication, security, and encryption requirements.

Client connection protocols.
VPN with Remote Access Solutions
Dial-Up
VPN
Client
Voluntary Tunnel
Compulsory Tunnel
VPN Server
Point of Presence (POP)
PSTN
ISDN
POP/Network
Access Server
(NAS)
VPN Server
Internet
VPN Server
RADIUS Server
POP/NAS
Compulsory Tunnel with RADIUS

VPN Connection Types

Account-based Authentication and Encryption

Compatibility with Other Operating Systems

Many organizations are transitioning from a centralized
in-house dial-up remote access infrastructure to an
Internet-based infrastructure for clients accessing a
corporate intranet. Organizations requiring support for
dial-up clients can reduce costs by outsourcing the
remote access dial-up points to an ISP. In addition, VPN
maintains a high level of security for client connections
to the private network.
A VPN supports secure point-to-point communications
over a private or public IP-based network. VPN
connections are Transmission Control Protocol (TCP)based and require no intermediate router support.
VPN Connection Types

VPN supports Internet Protocol (IP) layer tunneling that
creates a secure connection between a VPN-based
remote access client and a remote access server on the
private network. The computers participating in a VPN
connection authenticate one another and encrypt the
data flowing through the VPN.
Note: It is possible to create a tunnel and send the data
through the tunnel without encryption. However, it will
not be a VPN connection because the private data is
sent across a shared or public network in an
unencrypted form.

VPN connections can be designed as compulsory or
voluntary tunnels. Compulsory tunnels are preconfigured device-initiated connections for which:

The remote access server initiates tunnel connections.

The remote access server supports the tunnel protocol.


Client authentication is per user based and optionally
uses Remote Authentication Dial-In User Service
(RADIUS).
Client support for tunneling is not required

Voluntary tunnels are ad-hoc connections for which:

The dial-up user initiates tunnel connections.

Client support for tunneling protocols is required.

No intermediate remote access server support for
tunneling is required.
Account-based Authentication and Encryption

VPN enhances data security for a connection by:

Authenticating remote users prior to data exchange.

Encrypting authentication credentials.

Encrypting exchanged data.

Both Point-to-Point Tunneling Protocol (PPTP) and
Layer Two Tunneling Protocol (L2TP) support encrypted
and plain text authentication. When using L2TP and
Internet Protocol Security (IPSec) transport mode, VPN
authentication is based on an exchange of certificates
that prevents unauthorized access to resources and
data. Authentication certificates also provide a means of
sharing data encryption keys.
Compatibility with Other Operating Systems

The VPN technology is supported by a number of
vendors and operating systems, and is supported on a
number of remote access servers.
Although only Windows 2000 supports a VPN
configured for L2TP, any Windows 32-bit operating
system supports a VPN configured for PPTP.
Routing and Remote Access Features
NetBEUI
TCP/IP
NWLink
PPP
Internet
Remote
Access
Server


NetBEUI
NWLink
TCP/IP
SLIP PPP
Non-Microsoft
Communications Server
Provides Dial-Up Access

Supports various transport protocols

Supports various WAN technologies

Supports standard security protocols
Provides Server Interoperability
Dial-Up
Client

A Routing and Remote Access-based server supports
dial-up connectivity to a network. In addition to
providing access to directories and files, a remote
access server also handles authentication and
encryption for remote access clients.
Provides Dial-Up Access

Routing and Remote Access provides dial-up access for
remote user connections by using Point-to-Point
Protocol (PPP) or the Microsoft RAS protocol.
Supports various transport protocols

Over the communication channel, PPP allows
negotiation of the following protocols:


Transmission Control Protocol/Internet Protocol
(TCP/IP).
NetWare IPX/SPX/NetBIOS Compatible Transport
Protocol (NWLink).

NetBIOS Enhanced User Interface (NetBEUI).

AppleTalk protocol.

The Microsoft RAS protocol is a proprietary protocol
supporting dial-up clients by using the NetBEUI local
area network (LAN) protocol. The Microsoft RAS
protocol is supported in all previous versions of
Microsoft remote access and is used on Microsoft
Windows NT® version 3.1, Windows for Workgroups,
MS-DOS®, and LAN Manager clients. The remote access
server acts as a network basic input/output system
(NetBIOS) gateway for these remote clients.
Routing and Remote Access Features …

The NetBIOS gateway provides client access to
resources over:

NetBEUI.

NetBIOS over TCP/IP (NetBT) protocol.

NetBIOS over Internetwork Packet Exchange (IPX)
protocol.

Note: Routing and Remote Access does not support
Serial Line Internet Protocol (SLIP) clients, whereas the
Microsoft remote access client software does supports
SLIP connections.
Supports various WAN technologies

Dial-up remote access clients can connect to wide area
networks (WANs) by using the following methods:

Standard telephone lines with a modem (PSTN)

ISDN

X.25 direct connection or X.25 packet
assembler/disassembler (PAD)
Supports standard security protocols

Routing and Remote Access supports secured
authentication and data encryption. The remote access
server automatically negotiates authentication and
encryption levels with PPP-based remote access
clients.

For authentication, Routing and Remote Access supports:




Microsoft Challenge Handshake Authentication Protocol (MS-CHAP)
Microsoft Challenge Handshake Authentication Protocol, version 2
(MS-CHAP v2).
Challenge Handshake Authentication Protocol (CHAP).
Extensible Authentication Protocol-Transport Level Security (EAPTLS).

Shiva Password Authentication Protocol (SPAP).

Password Authentication Protocol (PAP).
Provides Server Interoperability

Remote access clients can access any PPP-based
remote access servers. These servers include:

Shiva LAN Rover.

NetWare Connect.

UNIX-based SLIP or PPP.

Other PPP-based communications servers.
Integration Benefits
DHCP
Server
DNS
Server
WINS
Server
RADIUS
Server
Active
Directory
IP
Address
Name Resolution
Name Resolution
Authentication and Accounting
Remote Access Policies
Remote
Access
Server

Routing and Remote Access integrates with other
Windows 2000 networking services to extend these
services to remote access clients and reduce network
management.
DHCP Integration

Integration with DHCP allows dynamic allocation of IP
address and configuration information to remote access
clients. This reduces configuration errors by eliminating
manual client configuration.

Routing and Remote Access leases blocks of 10 IP
addresses from DHCP for remote access clients. When
clients disconnect, the IP address is returned to the
pool.

If the remote access server is configured to use the
DHCP Relay Agent, all DHCP configuration information
is provided to the remote access clients through the
DHCP Relay Agent. If the DHCP Relay Agent is not
configured on the server, clients only receive the IP
address and subnet mask provided by the remote
access server.

Note: The TCP/IP options in DHCP can include specific
configuration information for remote access clients by
using the predefined user class RRAS.Microsoft to
define the required client options.
DNS Integration

DNS integration allows clients with dynamically
allocated IP addresses and configuration information to
update their name records in a Windows 2000-based
DNS server. This integration allows dial-up client DNS
names to be resolved in the same manner as clients
directly connected to the network.
WINS Integration

WINS integration allows dial-up clients with dynamically
allocated IP addresses and configuration information to
update their NetBIOS names in WINS. This integration
allows the NetBIOS resource names that are registered
by the dial-up client to be resolved in the same manner
as clients directly connected to the network.
RADIUS Integration

RADIUS integration centralizes the management of
multiple remote access servers. This integration allows:



Centralized administration of remote access policies.
Logging of client authentication success or failure from
multiple remote access servers.
Distributed authentication for clients in a heterogeneous
network.
Active Directory Integration

Integration of Routing and Remote Access with a
Windows 2000 native-mode domain allows the remote
access policies to be administered through the Active
Directory™ directory service. This integration provides:



Unified administration by using the Active Directory
management consoles.
Mapping of Windows 2000 users and groups to remote
access policies, which control dial-up connection
permissions.
Note: On a Windows 2000 remote access server, which
is a member of a Windows 2000 mixed mode, or
Microsoft Windows NT version 4.0 domain, a remote
access policy cannot be specified for a user account.
Designing a Functional Remote Access Solution

Integrating Remote Access Solutions into a LAN
Environment

Integrating Remote Access Solutions into a Routed
Environment

Integrating VPN into a Routed Environment

Selecting a Tunneling Protocol

Integrating VPN Servers with the Internet

Placing Remote Access Servers Within a Private
Network

Discussion: Evaluating Routing and Remote Access
Functional Requirements

The components of a Windows 2000-based dial-up
solution include Routing and Remote Access-based
servers, dial-up clients, LAN and remote access
protocols, WAN options, and security options. Routing
and Remote Access in Windows 2000 provides the
server-side components to support a dial-up solution.
To design a remote access solution based on Routing
and Remote Access, you must consider the network
access requirements, the protocols required, and the
server placement issues.
In this lesson you will learn about the following topics:

Integrating remote access solutions into a LAN
environment

Integrating remote access solutions into a routed
environment

Integrating VPN into a routed environment

Selecting a tunneling protocol

Integrating VPN servers with the Internet

Placing remote access servers within a private network
Integrating Remote Access Solutions into a LAN
Environment
Dial-Up
Clients
Remote Access Server
NetBEUI
TCP/IP
NWLink
PPP
Security Policies for Dial-Up Clients
Concurrent Sessions and Multilink
Aggregate Throughput for Clients
Client Configuration
Policies,
Groups
and
Users
LAN

A remote access solution for a nonrouted LAN can
provide a centralized dial-up facility for remote access
clients. Clients connecting to the remote access server
can be authenticated, provided with TCP/IP
configuration information, and allowed access to
resources on the network by using the permitted
protocols.

While designing a remote access solution for a
nonrouted LAN, you need to identify solutions for the
following:

The security model for administering remote access
permissions and connection settings in the remote
access server.
You can control access by individual user names, or by
Windows 2000 native-mode or mixed-mode Remote
Access Policies.

The number of concurrent sessions required to service
the dial-up clients.
This allows definition of the number of inbound ports
required. If PPP (Point-to-Point Protocol) Multilink
Protocol and Bandwidth Allocation Protocol (BAP) are
enabled, it may be necessary to provide more than one
connection point per client.

The aggregate throughput requirements for the clients.
The peak aggregate bandwidth required by the clients
must be equal to or less than the bandwidth available to
the LAN interface in the remote access server.

The TCP/IP configuration for the dial-up clients.
The allocation of IP addresses and a subnet mask can
be configured by the remote access server through preallocation to the client (allowing a fixed IP address), from
a fixed pool of addresses, from DHCP, and from the
Automatic Private IP Addressing (APIPA) addresses
(169.254.0.1 through 169.254.255.254).

The TCP/IP configuration for the dial-up clients with fixed
IP addresses.
The remote access server can configure the allocation of
IP addresses and a subnet mask through pre-allocation
to the client, thereby allowing a fixed IP address.
Note: Remote access policies must be defined to permit
users to request a fixed IP address, and you must
configure the dial-up properties of the user account with
a static IP address.

The TCP/IP configuration for the dial-up clients with
dynamic IP addresses.
The allocation of IP addresses and a subnet mask can
be configured by the remote access server from a fixed
pool of addresses, from DHCP, and from APIPA
addresses.
Note: If a DHCP Relay Agent is configured on the
remote access server, the client can request TCP/IP
options that are defined in the DHCP scope for the
subnet. If the DHCP Relay Agent is not configured, the
clients only receive the IP address and subnet mask
provided by the DHCP server.
Integrating Remote Access Solutions into a Routed
Environment

Selecting Dial-Up Solutions

Enabling Supported Protocols

Providing Client-to-Server Connections

Providing Demand-Dial Router-to-Router Connections

Before integrating a remote access solution into a
routed environment, you must consider the access
connection speed and connection type of the dial-up
users. You can constrain the functionality of any dial-up
remote access design by the access connection speed
and connection type.
Bandwidth limitations of LANs and WAN links, and the
dial-up connection speed, can place practical
constraints on the remote access implementation
design.
Selecting Dial-Up Solutions

Remote access servers can provide access to intranetbased resources by using dial-up connections. Dial-up
connections are used when the remote access clients
dial directly into modems attached to the organization's
remote access servers.

Consider implementing Routing and Remote Access dial-up
solutions if the:





Use of the Internet as a mechanism for accessing intranet-based
resources is considered an unacceptable risk.
Variability of the data throughput rate for an Internet connection is
insufficient to support client needs.
Logical connections consist of multiple physical connections, or the
connections are increased in response to client bandwidth
requirements.
Security aspects of the network design require additional security
features such as caller Identification (ID) verification or callback
support.
Cost of providing phone lines, modems, and multiport
communication adapters is not prohibitive.
Enabling Supported Protocols

Remote access servers support connectivity to remote
access clients by using multiple protocols. Certain
protocols may be required to access particular intranetbased resources or applications.

The following table lists the Routing and Remote Accessbased protocols and their features.
Choose
To provide
TCP/IP
Access to Web-based applications, File Transfer
Protocol (FTP) servers, or other applications that are
based on the TCP/IP protocol.
NWLink
Access to NetWare-based file and print servers by using
Internetwork Packet Exchange/Sequenced Packet
Exchange (IPX/SPX).
AppleTalk
Access to Apple Macintosh remote access clients by
using the AppleTalk Remote Access Protocol.
NetBEUI
Access to file and print resources in a small, nonrouted
LAN by using NetBIOS naming conventions.
Providing Client-to-Server Connections

Dial-up remote access solutions provide access to
intranet-based resources for remote access clients. A
dial-up remote access design must specify the:



Number of telephone lines, modems, adapters, or
asynchronous ports required to support the maximum
number of simultaneous client connections.
User accounts that will be granted remote access.
Remote access policy restrictions that apply to a user or
a group of users.
Providing Demand-Dial Router-to-Router
Connections

To support connectivity between remote locations, a
multiple remote access design must specify the:





Telephone lines, modems, and asynchronous ports
required for connecting the remote locations.
Routing capabilities found in the Routing and Remote
Access-based servers.
Demand-dial interfaces found in Routing and Remote
Access-based servers used to automate the initiation of
the connection between the locations.
User accounts used by the Routing and Remote Accessbased servers to authenticate each other.
Remote access policy restrictions.
Integrating VPN into a Routed Environment

Selecting Dial-Up or VPN-based Servers

Providing Remote Access Client Connections

A VPN implementation can support hundreds of VPN
remote access clients. However, the local network and
WAN links can place practical constraints on the VPN
design. Before selecting a VPN protocol and connection
type, evaluate your organizational needs and
environmental constraints. The VPN protocols provided
by Windows 2000 support a variety of operating
systems, security needs, and network designs.
Selecting Dial-Up or VPN-based Servers

Routing and Remote Access-based servers provide
access to intranet-based resources by using VPN or
dial-up connections. VPN connections are used when
remote access clients dial into an ISP and then
establish a virtual connection to the remote access
servers of an organization. Dial-up connections are
used when the remote access clients dial directly in to
modems attached to the remote access servers of the
organization.

Consider implementing VPN remote access servers if:



Using the Internet to access intranet-based resources is
an acceptable risk.
The organization's connection to the Internet supports
the aggregate throughput required for the maximum
number of concurrent remote access clients.
The variability of Internet bandwidth does not adversely
impact client response times.
Providing Remote Access Client Connections

Implementation designs that incorporate VPN servers
provide access to intranet-based resources by using
remote access clients. A VPN server design must
specify:

The number of PPTP or L2TP ports necessary to
support the maximum number of simultaneous clients.

The user accounts that are granted remote access.

Remote access policy restrictions.
Selecting a Tunneling Protocol
PPP Frame
PPTP
IP
GRE
PPP
Header Header Header
Encrypted PPP Payload
(IP Datagram, IPX Datagram)
Remote
Resource Server
Client
Remote
Access
Server
Secure Tunnel
over Existing
Network
L2TP/IPSec
IP
Header
Private
Network
PPP Frame
IPSec
UDP
L2TP
PPP
ESP
Header Header Header
Header
PPP Payload
(IP Datagram,
IPX Datagram)
Encrypted by IPSec
Signed
IPSec
ESP
Trailer
IPSec
Auth
Trailer

Dial-up clients may require secure connections to a
remote location, or to resources on a private network.
Routing and Remote Access in Windows 2000 supports
two tunneling protocols that provide authentication and
data encryption for creating VPN connections:

PPTP

L2TP
PPTP

PPTP is a de facto industry standard tunneling protocol that was
first supported in Windows NT 4.0. PPTP is an extension of PPP and
improves upon the authentication, compression, and encryption
mechanisms of PPP. Microsoft Point-to-Point Encryption (MPPE) is
used to encrypt PPP frames.
A PPTP frame consists of a PPP frame carrying the encrypted
payload with a Generic Routing Encapsulation (GRE) header. The
encrypted payload can be an IP datagram, an IPX datagram or a
NetBEUI frame.
By default, Routing and Remote Access is configured for 128 PPTP
ports. If your design requires more ports, then you must plan for
the creation of these ports.
If the Routing and Remote Access server is configured as a Virtual
private network (VPN) server using the Routing and Remote Access
Server setup wizard, then it is configured for 128 PPTP ports.
L2TP

L2TP-based virtual private networking connections are a
combination of L2TP and IPSec. L2TP uses the
authentication and compression methods of PPP, but
relies on IPSec transport mode for encryption services.

In an L2TP-based virtual private networking connection,
the sender and receiver must support both L2TP and
IPSec. The routers between the peer endpoints are
required to support only IP.
L2TP encapsulates the original payload inside a PPP
frame and performs compression whenever possible.
This compressed frame is then transported inside a
User Datagram Protocol (UDP) packet that is encrypted
by IPSec using an ESP header.

By default, Routing and Remote Access is configured
for 128 L2TP ports. If your design requires more ports,
then you must plan for the creation of these ports.

Note: IPSec can be used in tunnel mode without L2TP.
IPSec tunnel mode is not supported for clients in remote
access VPN scenarios. In this mode, IPSec is used for
interoperability with other routers, gateways, or end
systems.

Select compulsory VPN tunnels if the client cannot
support tunnel protocols directly. If clients can support
the VPN protocols, select voluntary end-to-end VPN
tunnels to provide the highest level of data protection.
Integrating VPN Servers with the Internet
Routing and Remote Access-based
Router
VPN Server
Internet
Firewall or NAT Device
VPN Server
Internet
Integrating VPN Servers and Firewalls
Integrating VPN Servers and NAT Devices

The placement of a VPN server can significantly affect
network security for a network that contains a firewall or
a network address translation (NAT) device. A correctly
placed VPN server must be accessible without
compromising network security.
Integrating VPN Servers and Firewalls

Firewalls filter IP traffic based on the IP address and
port number of the packet. Proper placement of the VPN
server relative to the firewall will achieve the
functionality, availability, and performance goals of the
design without compromising the security aspects of
the design.
Outside the firewall

Place the VPN server outside the firewall if:



Exposing the Routing and Remote Access-based VPN
server directly to the Internet does not compromise the
security aspects of the design.
The security risks associated with allowing access to the
entire VPN IP address range through the firewall are
unacceptable.
All sensitive data is placed behind the firewall, and all
remote access through the firewall is limited to the VPN
server.
If the VPN server resides outside the firewall, consider:

Providing an IPSec tunnel between the unprotected VPN
server and the Routing and Remote Access-based
router that is placed inside the firewall, to reduce the
number and complexity of the firewall filters.

Configuring the firewall to allow communication
between the unprotected VPN server and the Routing
and Remote Access-based router inside the firewall.

Encrypting all data between the unprotected VPN server
and the internal Routing and Remote Access-based
router by using the strongest encryption possible.
Inside the firewall

Place the VPN server inside the firewall if:



The added security risk of exposing the Routing and
Remote Access-based VPN server directly to the
Internet compromises the security aspects of the design.
The potential security problems associated with allowing
access to the entire VPN IP address range through the
firewall are acceptable.
If the VPN server resides inside the firewall, you must
configure the firewall filters to allow all PPTP-based and
L2TP-based traffic across the entire VPN IP address
range.
Integrating VPN Servers and NAT Devices

NAT devices, such as a proxy server, translate private IP
addresses into public IP addresses and vice-versa.
Some application servers directly record the IP address
and port number of the remote access client. These
applications require a translation table on the NAT
device to operate correctly. The NAT device modifies the
header of the IP packet in both directions to allow the
application to perform normally.
Using PPTP tunnels with a NAT device

When configuring NAT devices for PPTP tunnels,
remember that:


PPTP does not encrypt IP header, and it operates with
any NAT device.
The NAT device requires the appropriate application
translation tables.
Using L2TP tunnels with a NAT device

When configuring NAT devices for L2TP tunnels,
remember that:



When using IPSec with Encapsulating Security Payload
(ESP) to encrypt data, the IP headers are encrypted.
The NAT device cannot perform the modifications to the
IP header.
L2TP and IPSec with ESP encryption does not work with
applications that require NAT translation tables.
Placing Remote Access Servers Within a Private
Network
Firewall
Internet
Screened Subnet
Remote
Access
Server
Router
Multimedia
Server
Router
Router

Placing in a Subnet

Placing in a Screened Subnet

Placing in a Single Segment LAN
Resource
Server
WAN Link

In designing a remote access solution, you must
consider the position of the remote access server. The
placement of a remote access server in a network can
affect the delivery of data to remote access clients. It
can also affect the data traffic flowing to other users on
the network.
Placing the Remote Access Server in a Subnet

The server must be positioned in a subnet or on the
segment with the most client-accessible resources if:


There is a switched nonrouted LAN with multiple
physical segments. This position minimizes unicast
traffic flowing across segments, as the switch does not
reflect traffic onto all segments.
There is a routed network with multiple routers. Position
the remote access server to minimize cross-subnet
traffic. This position minimizes the effect of client data on
the bandwidth available to other network users.
Aggregate bandwidth considerations

The data for all dial-up clients passes through the
remote access server interface to the private network.
Even when the client data speeds are moderate, the
aggregate throughput required because of this
concentration can be significant. In any design,
wherever possible, you must minimize the routed path
to resources that are used by the dial-up clients.
Minimizing the routed path reduces both the client
traffic delays, and the interaction of dial-up client traffic
and normal network user traffic.

For example, consider a remote access server with
128*56 kilobits per second (Kbps) V.90 modems. If you
assume the following conditions:
1.
2.
At peak times all lines will be used.
A multimedia training application is running on the
remote access clients, requiring sustained throughput
of 38 Kbps from server to client.
The aggregate bandwidth required will be:
38Kbps * 128 = 4.864 megabits per second (Mbps)

The simplified throughput calculation shows that the
remote access server would use 49 percent of the
available bandwidth on a 10 Mbps Ethernet segment.
The LAN traffic of other network users would increase
this usage further and might make it impossible to
service the dial-up clients' multimedia needs. A possible
solution in this example is to move the multimedia files
onto the remote access server so that network access is
not required.
Placing the Remote Access Server in a Screened
Subnet
The server should be positioned in a screened subnet if:

Corporate policies exist with a mandate that client
access be processed by a firewall or filter.

Clients use a VPN tunnel to connect to the private
network.

The remote access server contains other data made
available to the public networks.

The majority of client resources exist in the screened
subnet.
Placing the Server in a Single Segment LAN

The remote access server can be positioned solely
based on physical network requirements if:


There is a single segment, non-switched LAN.
Clients are allowed to access only the remote access
server resources.
Discussion: Evaluating Routing and Remote Access
Functional Requirements
Remote Access Server
WINS
Clients
Subnet 1
Subnet 2
WINS Clients
Router A1
Router A2
Non-WINS
Clients
Router
Subnet 5
Windows 2000–based
Router
File and Print
Server
Subnet 3
Subnet 4
WINS
Clients
Windows Multimedia
Server

To provide a functional remote access solution for an
organization, you must decide on the number and
placement of servers based on the throughput and
access requirements of dial-up clients.
The following scenario describes an organization's
current network configuration. Read through the
scenario, and then answer the questions.
Scenario

An organization has decided to restructure an existing remote
access solution to give access to a larger number of employees. You
are assigned the task of evaluating the currently available
configuration and providing a viable solution for the new
requirements.
The current network configuration provides:

Intranet access to all shared folders and Web-based applications.

Access for 16 concurrent clients by using 56 Kbps modems.


Network architecture as shown in the preceding diagram, with the
routed network based on 10 Mbps Ethernet.
Support for a mission-critical Web-based application that requires 24hours-a-day, 7-days-a-week operation.
The organization requires the following new facilities:

Intranet access to all shared folders and Web-based
applications for remote access clients.

Access for a total of 160 concurrent clients by using 56
Kbps modems. This requires average throughput of 7.5
Kbps per client.

A solution that allows 36 of the concurrent clients to
access training video presentations on the Windows
Media™ Server. This requires sustained 28 Kbps
throughput per client.
Your are required to adhere to the following limitations:

The flow of data for remote access clients across
multiple subnets must be minimized wherever possible.

Remote access servers will be based on a corporate
standard computer purchase. The computer has a 10
Mbps network card and three 56 Kbps V.90 digital
interface cards, each supporting eight 56 Kbps V.90
client connections.
Securing a Remote Access Solution

Selecting the Appropriate Authentication Protocols

Selecting the Appropriate Encryption Methods

Ensuring Security with Remote Access Policies

Restricting Access to Private Network Resources

Distributing Authentication and Accounting Using
RADIUS

The security of a network can be compromised if remote
users are provided access to intranet-based resources.
An effective security configuration confirms the identity
of the clients attempting to access the resources on the
network, protects specific resources from inappropriate
access by users, and provides a simple, efficient way to
set up and maintain security on the network.

To help accomplish these goals, Routing and Remote
Access offers the following security features:



Prevents unauthorized remote access by using
appropriate authentication protocols.
Prevents unauthorized remote access by using
appropriate encryption methods.
Restricts access to the remote access server by using
remote access policies.

Restricts access to private network resources.

Authenticates user accounts by using RADIUS.
Selecting the Appropriate Authentication Protocols
Remote
Access
Server
Private
Network
Router
Dial-Up
Client
Authentication

To reduce the potential for unauthorized access,
Routing and Remote Access supports various
authentication protocols and encryptions methods.
Some of the protocols supported by Routing and
Remote Access provide enhanced authentication,
whereas other protocols that provide less security give
other benefits such as support for a wide diversity of
remote access clients.

The following table lists the authentication protocols
supported by Routing and Remote Access and describes
when to choose each protocol.
Choose
When
MS-CHAP
Providing encrypted authentication support for Microsoft Windows 95,
Microsoft Windows 98, Windows NT 4.0, or Windows 2000.
MS-CHAP v2
Providing encrypted authentication support for Windows 2000.
EAP-TLS
Providing encrypted authentication support for a smart card.The Routing and
Remote Access-based remote access server is a member of a mixed-mode or
native-mode domain in Windows 2000.The cost of adding a smart card reader to
each remote access client is not prohibitive.
CHAP
Providing encrypted authentication support for remote access clients that use a
diversity of operating systems.The client requires encrypted authentication.
SPAP
Providing encrypted authentication support for remote access clients by using
Shiva LAN Rover software.
PAP
Providing unencrypted authentication, and when the remote access clients
support no other protocol.
Selecting the Appropriate Encryption Methods
Remote
Access
Server
Dial-Up
Client
Private
Network
Router
Encryption

MPPE

L2TP over IPSec

The encryption methods supported by Routing and
Remote Access provide varying levels of encryption.
MPPE

MPPE uses RSA (public-key cipher for
encryption/decryption) RC4 stream cipher to encrypt
data for PPP or PPTP connections. MPPE can be
configured by using a remote access policy to use 40bit, 56-bit, or 128-bit encryption keys. The 40-bit and 56bit keys are designed for international use. The 128-bit
encryption keys are designed for North American use
and are available in only North American versions of
Windows 2000.
MPPE …

The following table shows the validation and encryption
options available for MPPE.
Validate by using Require data
encryption
Authentication methods Encryption enforcement
negotiated
Allow unsecured No
password
PAP, CHAP, SPAP, MSCHAP, MS-CHAP v2
Optional encryption (connect
even if no encryption)
Require secured
password
No
CHAP, MS-CHAP, MSCHAP v2
Optional encryption (connect
even if no encryption)
Require secured
password
Yes
MS-CHAP, MS-CHAP v2
MS-CHAP, MS-CHAP v2
Smart card
No
EAP/TLS
Optional encryption (connect
even if no encryption)
Smart card
Yes
EAP/TLS
Require encryption
(disconnect if server
declines)

Note: To enable MPPE-based data encryption for dial-up
or VPN connections, you must select the MS-CHAP, MSCHAP v2, or EAP-TLS authentication methods. These
authentication methods generate the required keys used
in the encryption process.

Choose MPPE as the remote access data encryption
method if:


Using the MS-CHAP, MS-CHAP v2, or EAP-TLS
authentication protocols.
User authentication is used and no machine certificate
infrastructure exists.
L2TP over IPSec

IPSec encrypts data within an L2TP-based connection.
IPSec uses machine-based certificates for
authentication, thereby reducing the ability of an
unauthorized computer to impersonate an authorized
computer.

Validate
by using
The following table describes the validation and encryption
options, and the authentication methods that are used
within an L2TP-based connection
Require
Authentication methods
data
negotiated
encryption
Encryption enforcement
Require
secured
No
password
CHAP, MS-CHAP, MSCHAP v2
Optional encryption (connect
even if no encryption)
Require
Yes
secured
password
CHAP, MS-CHAP, MSCHAP v2
Require encryption (disconnect
if server declines)
Smart
card
No
EAP/TLS
Optional encryption (connect
even if no encryption)
Smart
card
Yes
EAP/TLS
Require encryption (disconnect
if server declines)

The United States government eliminated export controls for most
computer hardware and software products that incorporate "strong
encryption" (symmetric key encryption with key lengths over 64
bits). Microsoft ships strong encryption capability in all products
where previous export limitations resulted in only 40-bit and 56-bit
Data Encryption Standard (DES) being available. In Windows 2000,
the conversion to 128-bit encryption affects encryption of files on
the disk, Internet Protocol (IP) Security, network driver interface
specification (NDIS) wide area network connections, Secure
Sockets Layer (SSL), and Terminal Services. Microsoft products
may not be exported to Afghanistan, Cuba, Iran, Iraq, Libya, North
Korea, Sudan, or Syria where export embargos are still enforced.

Choose IPSec as the remote access data encryption
method if:

Using L2TP tunneling.

A public certificate infrastructure exists.
Ensuring Security with Remote Access Policies
User Connection Request
N
Y
Have a Policy?
Reject
Connection
N
Y
Next Policy
Policy Match?
Y
Accept
Connection
User Deny?
Y
Remote Deny?
N
Y
User Allow?
Y
User Profile OK?
N

Remote access policies are a set of conditions and
connection settings that define remote access
permissions and usage. If the settings used for a dial-up
client do not match at least one of the remote access
policies that apply to the connection, the connection
attempt fails, regardless of the client dial-up settings.

Three models exist for defining remote access permissions and
connection settings:

Access restricted by user.
Permits implicit and explicit Allow access or Deny access decisions
on a user-by-user basis.

Access restricted by a policy in a Windows 2000 native-mode
domain.
Permits implicit and explicit Grant remote access or Deny remote
access decisions on a user or group basis.

Access restricted by a policy in a Windows 2000 mixed-mode
domain.
Permits implicit and explicit Allow access or Deny access decisions
on a user or group basis; it is implemented in the same manner as it
is implemented in Windows NT 4.0

Customizing the remote access policies can restrict
access to the remote access server by the:




Time of the day and day of the week.
Windows 2000 group to which the remote access user
belongs.
Type of connection being requested (Dial-up or VPN
connection).
Authentication and encryption types requested.
Restricting Access to Private Network Resources
Dial-Up
Client
Remote
Access
Server
IP Network
Network
Server
Properties of a Remote Access Server
Allow access
to IP network
by dial-up
clients

You can secure the network resources by limiting
access to the remote access or VPN server. The
resources made available to clients can be different
from the resources accessible to other users in the
network. For example, if remote access permissions are
given to employees and to a partner organization's staff,
the dial-up resources made available may be restricted
for the partner organization staff.
Access to resources can be restricted for dial-up clients
by:

Allowing access to only those resources that are on the
remote access server. This restriction is set on each
individual remote access server, and applies to all
clients who connect to the server.

Allowing access to resources on the routed network to
which the remote access server is attached. This
restriction is set on each individual remote access
server, and applies to all clients who connect to the
server.
Distributing Authentication and Accounting Using
RADIUS
Policy and
Authentication
Requests
RADIUS Client
Remote Access
Server and
RADIUS Client
Router
RADIUS Server
(Internet Authentication
Service)
Dial-Up Remote
Access Clients
UNIX Server and
RADIUS Server
Authentication
Requests
Windows 2000
Domain
Controller

RADIUS is a security authentication protocol based on
clients and servers, and is commonly used by ISPs on
non-Microsoft remote access servers.
Features of RADIUS

RADIUS provides the ability to authenticate remote user
accounts by using methods other than Windows 2000based authentication. For example, a remote access
server that uses RADIUS can authenticate remote users
by accessing a user account database located on a
UNIX system.

RADIUS centralizes the management of client
authentication and accounting for remote access
servers. The integration of Routing and Remote Access
with RADIUS allows centralized:


Remote access policies to be defined for all remote
access servers, replacing individual server policies.
Logging of client success, failure, and connection status
events for multiple servers.
The events to be logged include:

Authentication requests for the connecting user.

Authentication accepts and rejects for the connecting
user.

Accounting-interim requests, sent periodically by the
remote access server during a user session.
Enhancing a Remote Access Design for Availability

Adding Redundant Remote Access Servers

Centralizing the Management of Remote Access Servers
Using RADIUS

Discussion: Evaluating Routing and Remote Access
Security and Availability Requirements

The availability of a remote access implementation
design is measured by the percentage of time users are
able to obtain remote access to intranet-based
resources. Windows 2000 enhances remote access
availability by adding redundant remote access servers,
and by centralizing the management of remote access
servers.
In this lesson you will learn about the following topics:

Adding redundant remote access servers

Centralizing the management of remote access servers
using RADIUS

Evaluating routing and remote access security and
availability requirements
Adding Redundant Remote Access Servers




Using Connection Manager to Distribute Clients
Adding Remote Access Servers at Remote Locations
Using Multiple VPN Servers with Round Robin DNS
Entries
Using Windows Clustering with VPN Servers

Any design that requires high availability must include
more than one Routing and Remote Access-based
server or VPN server. The level of availability for
Routing and Remote Access is determined by the
requirements of the organization. Remote access
solutions with redundant servers can provide higher
availability for both dial-up and VPN clients.
Using Connection Manager to Distribute Clients

Dial-up remote access clients connect to the private network by
using a modem connected to a specific phone number. In the event
of a single point connection failure involving the phone line, the
modem, or the remote access server, connection to the private
network is lost. To provide remote access availability in the event of
a single point connection failure, consider:




Assigning each remote access client a primary phone number
connected to a designated remote access server.
Assigning each remote access client a backup phone number
connected to a redundant remote access server.
Using Connection Manager to call the primary phone number first,
and in the event of a failure, calling the backup phone number.
Using Connection Manager to distribute and update changes to the
access numbers for the intranet.
Adding Remote Access Servers at Remote Locations

In a design in which the remote access servers are centralized, a
connection failure between remote locations affects access to the
remote resources.To avoid this, consider distributing the remote
access servers to the remote locations if:





Connections between remote locations are unreliable.
Connections between remote locations are experiencing heavy
traffic.
Remote access clients tend to connect to resources in a single
location.
A reduction of phone charges results from calling local numbers.
Any design that requires high availability must include more than
one VPN server.
Using Multiple VPN Servers with Round Robin DNS
Entries

The round robin DNS entries must be with the same
fully qualified domain name (FQDN), while also using
the IP address of the respective VPN servers. Multiple
round robin DNS entries are processed in the sequence
found in the DNS database. When a server has more
than one round robin entry in the DNS database, the
server is accessed a corresponding number of times in
sequence.

When using multiple VPN servers and round robin DNS
to provide high availability:




Ensure that a round robin DNS entry exists for each
VPN server.
Add additional round robin DNS entries when specific
VPN servers support a greater number of remote access
clients than other VPN servers.
Know that the design consumes fewer system resources
than a design that uses Windows Clustering.
Be aware that the VPN server failover is not automatic,
and remote access clients receive time-out messages
when attempting to connect to inactive VPN servers.
Using Windows Clustering with VPN Servers

You can use Network Load Balancing, one of the
Windows 2000 Advanced Server features that make up
Windows Clustering, to improve the availability of
Internet Information Server (IIS), proxy, DNS, FTP, VPN,
and streaming media servers. Network Load Balancing
clusters provide high scalability and availability by
combining up to 32 servers running Windows 2000
Advanced Server into a single cluster. Windows
Clustering provides complete VPN server redundancy
and centralized administration of the cluster.

When using multiple VPN servers and Windows
Clustering to provide high availability:


Ensure that all servers in the same cluster have a highspeed, persistent connection.
Be aware that VPN server failover is automatic and
remote access clients do not receive time-out messages
when attempting to connect to inactive VPN servers.
Centralizing the Management of Remote Access
Servers Using RADIUS

Distributing Remote Access Policies to All Servers

Providing Redundant Authentication and Accounting

RADIUS centralizes the administration of remote access
policies by configuring all remote access and VPN
servers to share a common policy. Also, RADIUS
inherently provides for centralized accounting of logon
status.
In organizations in which RADIUS is not used, remote
access policies are configured on each remote access
and VPN server. In addition, the log files that track user
authentication success or failure are located on each
remote access server. This complicates the
management process because the system administrator
has to manage multiple servers.

Multiple remote access servers use RADIUS to
centralize the:

Administration of remote access policies.

Logging of authentication success or failure.
Discussion: Evaluating Routing and Remote Access
Security and Availability Requirements
ISP/Internet Connection
WINS
Clients
Subnet 1
7 Remote Access Servers
and 1 VPN/Proxy Server
WINS Clients
Subnet 2
Router A2
Non-WINS
Clients
Router A1
Subnet 5
Windows 2000–based
Router
File and Print
Server
Subnet 3
Subnet 4
WINS
Clients
Windows Multimedia
Server

To provide a highly available and secure remote access
solution for an organization, you must decide on the
number and placement of servers, and the security
requirements of the organization and clients.
The following scenario describes an organization's
current network configuration. Read through the
scenario, and then answer the questions.
Scenario

An organization has decided to restructure an existing
remote access solution to improve security and
availability. You are assigned the task of evaluating the
currently available configuration and providing a viable
solution for the new requirements.
The current network configuration provides:

Intranet access to all shared folders and Web-based applications.

Internet connectivity by using a single computer VPN/proxy/firewall
connection to an ISP.

Access for 160 concurrent clients by using 56 Kbps modems.

Access for 10 clients who use VPN access to the network.

Network architecture as shown in the preceding diagram with the
routed network based on 10 Mbps Ethernet.

Support for a mission-critical Web-based application that requires
24-hours-a-day, 7-days-a-week operation.

Remote access servers that are based on a corporate standard
computer purchase. The computer has a 10 Mbps network card and
three 56 Kbps V.90 digital interface cards, each supporting eight 56
Kbps V.90 client connections.
Optimizing the Remote Access Design for
Performance

Distributing Remote Access Across Multiple Servers

Improving Remote Access Performance on a Server

In a remote access or VPN solution, the increase in the
number of client connections can affect the
performance of the solution. You must improve the
performance of individual servers, or share the load of
servers by including additional servers in the network
design as the number of remote access clients
increases.

In this lesson you will learn about the following topics:

Distributing remote access across multiple servers

Improving remote access performance on a server
Distributing Remote Access Across Multiple Servers

Using Connection Manager to Distribute Clients
 Evaluate and then redistribute remote access clients
across remote access servers
 Provide a new phone book that reflects the redistribution

Adding Remote Access Servers at Remote Locations
 Distributes network load to the location where the
resource resides
 Improves remote access performance

Adding VPN Servers

Factors such as changes in client application usage,
WAN usage, and number of clients can affect the
performance of a remote access server. A possible
solution for the performance degradation is to use
multiple remote access servers and distribute the client
load across the servers.
Using Connection Manager to Distribute Clients

In a multiple-server remote access solution, the clients
must be distributed evenly across the servers.
Connection Manager allows the distribution of a phone
book with multiple access numbers to clients. The
clients connect to the dial-up numbers in the order
specified in their phone book. The order of the phone
book entries can be set for individual users or groups,
allowing the client load to be evenly distributed between
servers.
Adding Remote Access Servers at Remote Locations

Adding remote access servers at remote locations may
improve performance where clients access local
resources. At each remote location, install the
appropriate number of remote access servers to
support the clients that dial-up to access resources.
Install remote access servers at remote locations if:



The cost of the additional remote access servers is
acceptable.
The dial-up clients mostly access local resources.
A significant reduction of phone charges results from
calling local numbers.
Adding VPN Servers

Create VPN server designs by adding multiple VPN
servers in a load-balancing configuration. These
redundant servers distribute the remote access clients
in a manner that divides total resource usage across all
of the servers.
Improving Remote Access Performance on a Server

Improving Single Server Performance

Dedicating a Server to Remote Access and VPN Servers

Upgrading Existing Remote Access and VPN Servers

Improving WAN and LAN Connection Performance

Routing and Remote Access enhances server
performance by supporting multiple CPUs that can be
used by the multithreaded service. You can select a
solution to enhance the performance of the server,
depending on the components limiting the performance
of the server.
Improving Single Server Performance

The following table lists the performance-limiting factors
with the possible solutions.
If the performance-limiting factor is
Consider
Client connection speed
Upgrading to modems that support a higher
transmission rate.
Upgrading to intelligent communications
adapters to offload processing from the
remote access server.
Using multiple or higher bandwidth network
cards for the private and public network
connection.
Remote access server connection
Individual computer
Minimizing or offloading other services
running on the computer.
Adding multiple CPUs.
Providing ample memory to support the
service.

Note: If the remote access server is also providing
resources for remote access clients, the performance of
the disk subsystems might become a limiting factor.
Under these circumstances, the disk subsystem
performance may be improved by using redundant array
of independent disks (RAID) arrays.
Dedicating a Server As a Remote Access and VPN
Server

In some designs, remote access and VPN servers share
resources with other services and applications on the
same physical computer. If performance is not
achieving the design specifications, move all other
functions to a separate computer. Consider dedicating a
server to remote access or VPN if:



Other functions running on the same computer can be
transferred to another system.
The cost of adding the additional server is acceptable.
The existing server hardware cannot be upgraded
further.
Upgrading Existing Remote Access and VPN Servers

When the resources of the VPN server are exhausted,
the performance degrades relative to the degree to
which the resources are used. After enough resources
are depleted, the performance of the VPN server does
not achieve the design specifications. Consider
upgrading the existing VPN servers if:

Other functions must run on the same computer.

The cost of adding the additional server is unacceptable.

The existing VPN server hardware supports future
upgrades.
Improving WAN and LAN Connection Performance

In a proper design of remote access and VPN servers,
the maximum data rate of the Internet or intranet
connection must be the limiting factor in accessing
resources. For example, if the design specifies the use
of 256 Kbps asymmetric digital subscriber line (ADSL)
connections for remote access clients, clients must
expect data transmission rates near 256 Kbps.
To improve the data throughput rates, consider:

Upgrading to an ISP that provides improved data rates.

Upgrading to intelligent communications adapters to
offload processing from the server.
Lab: Designing a Remote Access Solution
Objectives
After completing this lab, you will be able to:

Evaluate a scenario to determine the requirements for a
Routing and Remote Access design.

Design a Routing and Remote Access solution for the
given scenario.
Prerequisites
Before working on this lab, you must have:

Knowledge of Routing and Remote Access features and
functionality.

Knowledge of Routing and Remote Access strategies
for security, availability, and performance.
Exercise 1: Making Remote Access Implementation
Decisions

In this exercise, you will design a remote access
solution for the given scenario. Review the diagrams
and the scenario. Answer the questions provided to
complete your solution to the scenario.
Scenario

An organization has decided to restructure an existing
remote access-based solution to its private network.
You are assigned the task of evaluating how dial-up
remote access is used in the existing physical network
design.
The current network configuration provides:

Intranet access to all shared folders and Web-based applications at all
locations.

Access to the Internet from all locations.

Remote access to corporate resources, regardless of a single server
failure, for 60 remote staff members.

Support for all of the hosts, as shown in the diagram.

Support for dial-up clients with a mixture of 33.6 and 56 Kbps modems.

Support for a mission-critical Web-based application that requires 24hours-a-day, 7-days-a-week availability.

Remote access to shared folder resources on Windows 2000 and Novell
NetWare 3.x-based servers, and to Web-based applications and files,
including a sales multimedia presentation requiring sustained 28 Kbps
throughput.

Isolation of the organization's network from the Internet by using a proxy
server and a firewall, both situated at LocationA.

Encryption for all remote communications authentication and data.
In the current scenario:

Each remote user consumes an average of two percent
of the remote access server's resources with an inactive
baseline of four percent.

Corporate guidelines for resource computers and
servers require that average usage not be above 70
percent.

Average data rates for remote clients do not fall below
30 Kbps.
High Level Network Design

The following diagram shows an overview of the existing
network configuration. Each location is shown in detail in
subsequent diagrams.
LocationA Network Design

The following diagram shows the existing network
configuration at LocationA.
LocationB Network Design

The following diagram shows the existing network
configuration at LocationB.
LocationC Network Design

The following diagram shows the existing network
configuration at LocationC.
Review

Introducing Routing and Remote Access

Designing a Functional Remote Access Solution

Securing a Remote Access Solution

Enhancing a Remote Access Design for Availability

Optimizing a Remote Access Design for Performance