Windows Server 2008 R2 includes several features and
services that allow the server operating system to work in tandem with
Windows 7, the client operating system. Features such as BranchCache and
DirectAccess require Windows Server 2008 R2-based servers, and Windows 7
clients. Due to this requirement, you may want to consider deploying
Windows 7 along with, or shortly after, your Windows Server 2008 R2
Overview of Branchcache
BranchCache is a new feature available in Windows Server 2008 R2
and Windows 7. BranchCache provides a better end-user experience for
users opening files across a Wide Area Network (WAN) by caching a copy
in the branch office after the document or intranet Web site is opened
for the first time. The cached copy can be stored on a branch office
server running Windows Server 2008 R2 (hosted mode) or a Windows 7
client (distributed mode). When a second client attempts to open the
same file, it is opened from the cached copy as opposed to attempting to
access the file over the WAN. Figure 1 depicts what a typical BranchCache deployment might look like.
Figure 1. Example Branchcache deployment.
deploying BranchCache, you can not only improve the end-user experience,
but also decrease traffic load on your WAN circuits. However it is
important to remember that to take advantage of BranchCache, you need to
deploy both Windows Server 2008 R2 servers (for hosted mode) and
Windows 7 clients (for client access and distributed mode).
BranchCache used for read access only
BranchCache is used for
reading a file or Web site only. Write operations require the client to
perform the write process back to the original source across the WAN.
Planning to Deploy Branchcache
Prior to installing
BranchCache on your network, you need to properly design and plan for
your deployment. As with all features, you should properly test the
deployment in a lab to verify your design and configurations. In this
section, we will discuss things you need to consider when planning to
deploy BranchCache within your organization.
BranchCache can be deployed in the following modes:
—BranchCache Hosted mode uses a Windows Server 2008 R2 server located
in the BranchOffice to store the cache. When Windows 7 clients access a
cached copy of a file or Web site, they access it on the branch office
server with BranchCache installed. Hosted mode is recommended for larger
branch offices, and offices that have a considerable amount of mobile
—BranchCache Distributed mode uses Windows 7 clients to host the branch
office cache. When a Windows 7 client accesses a cached copy of a file,
it pulls it from the cache of a peer Windows 7 computer. This does not
require a Windows server in the branch office but if a computer with a
cached copy of a file is offline, the other branch office computers must
pull a new copy from the original source across the WAN. Distributed
mode is recommended only for offices with less than 15 users and
preferably with mostly desktop workstations. Figure 2 depicts how distributed mode works in Windows 7.
Figure 2. Branchcache using distributed mode.
BranchCache Distributed Mode security
Even though BranchCache deployed
in Distributed mode uses a peer-to-peer configuration, file security is
still enforced. When using distributed mode, the local cache is
encrypted and can be accessed only by users that have been given access
to the specific files.
deploying BranchCache, you will need to select the mode that best fits
your branch office locations. You must choose a mode for each office;
however, you can mix modes between branch offices. For example, a larger
office with 100 users can have a hosted mode deployment, while a
smaller office of 10 users can use distributed mode.
use of BranchCache requires that client and servers meet certain
minimum operating system requirements. The main operating system
requirements are outlined here.
Hosted BranchCache mode
—When using hosted BranchCache mode, the branch office cache server
must be running Windows Server 2008 R2 Enterprise, Windows Server 2008
R2 Itanium, or Windows Server 2008 R2 Datacenter editions.
Distributed BranchCache mode
—Distributed mode requires that all clients, which also host the cached
copy of files, be running Windows 7 Enterprise or Windows 7 Ultimate.
Client computers —Client computers must be running Windows 7 Enterprise or Windows 7 Ultimate to take advantage of BranchCache.
Additionally, any Web server
that you wish to be cached in branch offices requires that the
BranchCache feature be installed. For source servers that you wish to
allow files to be cached in branch offices, you will need to install the
BranchCache for Network Files role.
When deploying BranchCache
using hosted mode, each branch server hosting the cache will need a
certificate from an internal Public Key Infrastructure (PKI) or
third-party certificate provider.
BranchCache and WAN accelerators
BranchCache cannot be used
across WAN connections that are using WAN acceleration appliances. These
devices are configured to compress and optimize data performance across
a WAN. If your network uses any of these devices, you will more than
likely not be able to set up and use BranchCache.
Designing a BranchCache deployment
There are several aspects to designing a BranchCache deployment. You need to consider things such as
workstations in branch offices. In larger branch offices, you may need
to use multiple servers to cache content for performance reasons. The
number of workstations may impact on your decision to deploy a hosted
deployment or a distributed deployment.
branch office users mobile or stationary? If you have a highly mobile
workforce, it may not be efficient to deploy BranchCache in a
workstations running Windows 7? If you still have workstations on your
network running Windows XP, they will not take advantage of BranchCache
the branch office have servers deployed? If there are no servers in the
branch office you will need to deploy them if you plan to use a hosted
using a distributed deployment, how much disk space is available on
workstations? If your workstations in the branch office do not have
adequate disk space available, they will not be able to cache files
If using hosted deployment, you will need to deploy a certificate authority to obtain a third-party certificate.
You will need to properly
document and test your design before rolling into production. As with
all deployments, proper testing needs to be performed before making
modifications to your production environment. The figures given earlier
in this section depict what a typical BranchCache design might look
like. You will want to create similar drawings of your deployment as
part of your design process.