Tag Archives: Exchange2013

Microsoft Exchange Conference 2012, a Summary

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After being absent for over 10 years, this year the most anticipated conference for Exchange minded people took place in Orlando, Florida (US), the Microsoft Exchange Conference 2012 (MEC).

Despite not being able to attend MEC 2012, I’d like to summarize the news on Exchange 2013 from the event. Some of this information went public as part of the release of Exchange 2013 Preview, which was released in July (yes, almost 2 months ago – time flies). Some statements were new, like for example the expected release date of Exchange 2010 SP3, which is required for co-existence with Exchange 2013.

With all the social media nowadays, you can track most of the statements made at the event. Thanks to people like Jeff Guillet and Devin Ganger and people from our The UC Architects group, like  Dave Stork, Michael van Horenbeeck, Pat Richard, Serkan Varoglu and John A. Cook, who reported live from the sessions they were attending (hastag #iammec), the community was kept up to date with information as it unfolded. At each the end of the day, Tony Redmond gave a nice summary including comments on the event as a whole.

Picture shows some of people behind The UC Architects together
with Perry Clarke (GM Exchange), who you might recognize from
the Ask Perry videos. The picture is taken by Tony Redmond.

The information presented here is a summary of all the information provided through social media and is additional to the information presented at the release of Exchange 2013 Preview; you can read all about that in my Changes in Exchange 2013 Preview article. It is in no way meant to be conclusive or complete.

Ok, now on to the goodness.

Co-Existence
Exchange 2010 Service Pack 3 is expected to be released in the first half of 2013. Not only is it required for co-existence with Exchange 2013, it also supports Windows Server 2012 as Operating System platform. Note that SP3 will require a schema update.

No word on the expected release date of the update required for Exchange 2007 to support co-existence between Exchange 2013 and Exchange 2007. Since Exchange 2007 SP3 Rollup 8 was released in August, thus after the Exchange 2013 Preview became available, I assume we have to wait for Rollup 9 (or 10?).

Storage
Ross Smith from the Exchange Team confirmed the 99% IOPS reduction claim when comparing Exchange 2013 with Exchange 2003; when compared with Exchange 2010 it’s a 50% reduction. That’s down from 1 IOPS per mailbox in Exchange 2003 to .125 IOPS in Exchange 2010 to a 0,0625 IOPS per mailbox in Exchange 2013.

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Also, passive copies have around 50% reduction in IOPS, mainly due to the increased checkpoint depth (100MB) and less aggressive pre-reading of data to keep in line with the checkpoint depth (I’ll devote a separate article on this at a later date). This means when mixing active and passive copies on a Mailbox server, the passive copies play more nicely from a storage perspective. Also, because of these changes database fail-over times are down from 20 seconds in Exchange 2010 to about 10 seconds in Exchange 2013.

To validate storage for Exchange 2013, JetStress for Exchange 2013 will become available 3 months after Exchange 2013 goes RTM. When required to validate storage in the mean time, it is recommended to utilize Exchange 2010’s version of JetStress since Exchange 2010 and Exchange 2013 will have the same IO pattern.

Databases
In Exchange 2013, multiple databases per storage volume allowed, which allows for active and passive copies on the same volume. Looking at the lower IOPS requirements of Exchange 2013 ESE’s engine and the 50% lower IOPS factor of passive copies, this allows for some serious consolidation on large volumes. The number of volume copies must match the number of databases per copy.

Note that putting databases on SMB3 shares (Windows Server 2012) is not supported; putting a virtualized Exchange server on SMB3 shares is.

Mailboxes
Besides the recommendation to embrace 7,200 RPM disks for Exchange storage, large mailbox implementations are expected to take off (100GB+, including mailbox, archive and recoverable items) in an ongoing battle to get rid of PSTs and 3rd party solutions.

Due to database accounting changes in Exchange 2013, mailboxes may see a 30% increase in size when moved from Exchange 2010 to Exchange 2013. Make sure you adjust mailbox quota settings accordingly.

Client Access
CAS 2013 will proxy client traffic to Exchange 2010 using the CAS 2010 server’s FQDN, i.e. it won’t determine or use internalURL or InternalNLBBypassUrl. You can’t configure CAS-to-CAS proxying per site; it’s an all or nothing setting. At RTM, Exchange 2013 Client Access servers won’t contain support for SSL offloading.

Health Checking
Exchange 2013 will not only check the server’s health looking at the Exchange services, but it will also check the protocols.

CAS 2013 will determine the health of legacy Exchange servers using a simple HTTP HEAD call.

Automatic Reseeding
Besides the ability to seed databases using multiple sources, which prevents the situation where multiple remote copies are seeded over WAN links from the active copy, Exchange 2013 contains a feature called Automatic Database Reseeding or just AutoReseed.

AutoReseed can be utilized to automatically reseed databases when required, e.g. after a storage failure. AutoReseed can even allocate and initialize spare disks to restore database redundancy. AutoReseed requires configuring three new properties, which are part of the DAG:

  • AutoDagVolumesRootFolderPath refers to the mount point containing all available volumes, including spare volumes;
  • AutoDagDatabasesRootFolderPath refers to the mount point containing the databases;
  • AutoDagDatabaseCopiesPerVolume sets the number of databases copies per volume.

So for example, when you’ve configured a mount point C:\Volumes (AutoDagVolumesRootFolderPath) containing mount points for databases, e.g. C:\Volumes\DB1, and mount point C:\Databases (AutoDagDatabasesRootFolderPath) with mount points to Exchange databases, e.g. C:\Databases\DB1 (where C:\Databases\DB1 maps to C:\Volumes\DB1), and DB1 contains folders for database and logfiles, AutoReseed can utilize mount points from C:\Volumes to automatically recreate and reseed databases when DB1 fails.

Site Resilience
Exchange 2013 will feature an automatic site (datacenter) fail-over using a witness server located in a 3rd well-connected site. This enables customers to automate the process of site switchovers, from primary to secondary site. This feature is optional.

This may confuse existing Exchange customers, who perhaps learned with Exchange 2007 a 3rd site for the cluster voter was not recommended, after which it shortly became an option with Exchange 2010. Then, after a while an adjusted recommendation was published not to use a 3rd site and now it’s option again,

Despite this, I think this certainly is a valuable feature. Normally, site outages and datacenter switchovers are stressful situations; if it’s preconfigured and automated, the less prone to error the switchover process is.

Exchange fellow and colleague Jaap Wesselius, who did
2 sessions on Load Balancing Exchange, was interviewed
by F5. Click the image to watch the interview.

Exchange Online
You can use Exchange 2003 with Exchange 2013 Online (when it becomes available) by utilizing an Exchange 2010 CAS server, just like today.

Safety Net
Safety Net is the new transport dumpster in Exchange 2013 and will provide similar functionality. It will also take over the functionality of Shadow Redundancy, which purpose in Exchange 2010 is to guarantee delivery of messages and accommodate for transport failure. Lagged Copy functionality is also enhanced by Safety Net, since you can activate lagged copies by activating the (lagging) copy after which Exchange 2013 will use Safety Net to make the database current. How long Safety Net will hold messages is a configurable setting.

Compliance
Exchange 2013 will support Litigation Hold, Time-based Hold (rolling data, e.g. items aged X days) and In-place Hold (formerly known as Legal Hold).

Unified Messaging
The Exchange 2013 UM role has a 100 concurrent calls limit. As you probably know, in Exchange 2013 Mailbox servers are used for UM as well. Because of that, this limit will have serious consequences when you’re designing an environment using several big servers; you might be forced to distribute the workload over more, lighter servers.

Exchange 2013 and ForeFront Treat Management Gateway
Exchange 2013 will work fine in conjunction with ForeFront TMG, except for maps feature when using TMG’s Forms-Based Authentication (FBA); the only thing you need to adjust is the logoff URL. Note that despite the ForeFront TMG 2010 End-of-Life statement from Microsoft last week, people like Greg Taylor (Program Manager Exchange) emphasized customers shouldn’t avoid using or opting for TMG while it is still available.

Public Folders
Migration of Public Folders from Exchange 2007 or Exchange 2010 is a cut-over scenario, so there will be no co-existence.

When using Exchange 2013 Public Folders next to Public Folders on Exchange 2007 or Exchange 2010, you need to manually map those to related folders in Exchange 2013 using CSV file.

Emphasis was put on being able to control Public Folders and put that data in the same store is worth losing the multi-master functionality.

Exhibitor ENow Consulting held a contest
for collecting the most autographs.

Message Hygiene
Exchange 2013 will include tools to block messages in a certain character set. This is useful in scenarios where you don’t expect messages in one of the Chinese languages and you want to block (potential) spam written in one of those languages.

In-Place Archiving
The new term for Personal Archive or Online Archive is In-place Archiving.

Message Routing
Exchange 2013 won’t use least-cost routing when routing messages, but it will use it to determine if Hub sites are defined. Exchange 2013 will honor Hub site definitions, but there are to be considered legacy.

A Delivery Group is a set of transport servers responsible for delivering messages to a certain routing destination. There are several types of Delivery Groups, depending on the destination, e.g. DAG or Site. Each transport server is used in a Round-Robin fashion when delivering messages.

An MBX server and CAS server listen for incoming messages on port 25 unless co-located; then the MBX server will listen on port 2525.

More background information on message routing in Exchange 2013 also in conjunction with Exchange 2010 is to be found here.

Licensing
It is no longer required to have an Enterprise license for eDiscovery; it is still required to have an Enterprise license when using Legal Hold.

Virtualization
Many statements were made to de-emphasize virtualizing Exchange and only use if for testing purposes. When virtualizing, the same rules apply as for Exchange 2010.

Like with earlier versions of Exchange, the ESE engine will claim memory at startup using the amount of physical ram. Configuring Dynamic Memory is therefor not only pointless but also not recommended, like I stated in an earlier post on Exchange and Dynamic Memory.

It is also emphasized that putting VMDK files on VMWare NFS disks is not a supported scenario, so I assume this is often seen in the field despite not being supported from Microsoft.

Mobile
ActiveSync in Exchange 2013 will cause 65% less RPC communications over Exchange 2010.

Outlook Web Access
When using OWA 2013 in offline mode, the locally generated cache file isn’t secure; use of BitLocker is recommended. Single Sign-On in combination with OWA on Exchange 2013 redirection will be fixed post-RTM. Also, be advised that at RTM, OWA in Exchange 2013 won’t have support for Public Folders.

IAMMEC Portal
A portal for the Exchange community was announced, iammec.com. Here, people involved with Exchange can get information from within Microsoft or other sources. How this will differ from the Exchange related topics on TechNet forum is to be seen.

It is unknown if there will be a MEC in 2013; Microsoft’s director of PM for Exchange, Michael Atalla, said there will a MEC when “theres’s something  to talk about”. It is rumored that recordings of the 1st day of the conference will be made available at a later date, except for the interactive sessions.

PS: The icon accompanying this article is the Exchange 2013 logo.

TechEd Australia 2012 sessions

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With the TechEd Australia 2012 event behind us, recordings and slide decks of finished sessions are becoming available online. Here’s an overview of the Exchange-related sessions:

Lync related sessions:

Note: Not all sessions are available online yet but I expect they will be at a later time so check back later.

Changes in Exchange 2013 Preview

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Note: This article is based on a pre-release product and may therefor be subject to changes.

Here’s an short list of the changes and notes regarding Exchange 2013, compared to Exchange 2010:

Goodbye EMC, Hello EAC
The Exchange Management Console (EMC) is no more. A new web-based management interface, the Exchange Administration Center (EAC), replaces EMC and ECP (organization management functions). The EAC provides a single console for on-premise, hybrid or online deployments and doesn’t require installation of management tools.

EAC can also be used to manage Public Folders and contains functionality to run reports on mailbox or administrator audit logs.

Less roles is more
Exchange 2013 reduces the number of Exchange server roles to two: Client Access Front End server and Mailbox server (Exchange 2003 Front-End/Back-End anyone?):

  • Client Access Front End servers will only proxy or process client traffic. They consist the known Client Access Server services as well as the Front End Transport Service component that deals with mail transport, hence the term Client Access Front End or CAFE. Multiple CAFE servers can still be organized in Client Access Arrays. New in Exchange 2013 is that client connections are stateless, which means you can utilize simple layer 4 (based on IP address or port) load balancing solutions or DNS Round Robin when requirements permit. Since connections are stateless, I expect client experience to improve as well as clients shouldn’t notice when being failed over to a different CAS server;
  • Mailbox servers are used for data storage and UM. Multiple Mailbox servers can still be organized in clusters using Database Availability Groups.

If you require an Edge Transport server, you can use Exchange 2010 or even Exchange 2007 Edge Transport servers in combination with Exchange 2013.

Transport Servers MIA?
In Exchange 2013, mail flow is dealt with by both the Client Access server and the Mailbox server. The Client Access server hosts a service called Front End Transport service which will process messages from or to external sources. The Mailbox server hosts two transport-related services, Hub Transport and Mailbox Transport service, which will process messages from or to other Mailbox servers or deal with the retrieval or storage of messages.

Transport pipeline overview diagram

Because the transport services are now co-located with Mailbox and Client Access servers, I do foresee challenges for organizations who designed infrastructure and farms purely for routing and processing messages. Of course, Mailbox servers will perform the same job, next to serving mailboxes, but this defeats the best practice of reducing attack surface by splitting roles.

This architecture found in Exchange 2010 didn’t exist in Exchange 2003 (but could come a long way by hardening servers). Then came Exchange 2007 with its server role architecture, which made a lot of sense for large environments (of course, there’s always the option of co-locating server roles). Now, wtih this reduction of server roles, I know at least 1 customer who will ponder on creating hardening guides for Exchange 2013 when the time comes.

Au revoir, MAPI
MAPI (RPC) will be dropped in Exchange 2013, leaving Outlook Anywhere (RPC over HTTPS) access as the protocol of choice for clients (IMAP/POP access still there). This means less holes to put in firewalls (only HTTPS), easier load balancing configurations, a single client endpoint (which also has benefits from a certificate perspective), etc. Of course there are also downsides, like Outlook 2003 doesn’t work and tools may stop working.

Public Folders
Unlike Exchange 2010, where Microsoft in early announcements mentioned the possible deprecation of Public Folders, Microsoft leaves no doubt when it comes to Public Folders and Exchange 2013. In fact, Microsoft made some interesting changes to the Public Folders architecture, where Public Folders reside in mailbox databases utilizing mailboxes (i.e. Public Folder Mailboxes).

This architectural change enables Public Folders to basically have the same benefits as Mailboxes in Mailbox databases, e.g. cluster continuous replication better known as Database Availability Groups. While this has serious implications for the migration scenario, it might prove a better alternative the “move to Sharepoint” cliché. It also requires rethinking placement of mailbox databases; while public folders utilize a multi-master model, where a branch office could make changes in local public folder database which replicated throughout the organization, Database Availability Groups utilizes a single master model, meaning with Exchange 2013 public folder clients must connect to the writable mailbox database copy.

The feeling that Microsoft is serious again about Public Folders is also driven by the fact that the next version of Exchange Online, part of the next version of Office 365 which confusingly is called Office 365 Preview, contains Public Folders. That’s right, Public Folders in Office 365; who thought that would ever happen, raise your hands. Check out Office 365 Preview here.

Outlook Web Access support for Exchange 2013’s Public Folders is expected in Exchange 2013 SP1.

Storage Engine
Exchange 2013 sticks with the ESE as the database engine of choice. The Information Store processes, now called Managed Store, have been revised, utilizing per database processes which enable faster fail-over and improved resilience. The engine integrates Microsoft’s FAST indexing engine.

Additionally, Microsoft expects another 50% IOPS reduction (which would mean 1/8th of Exchange 2003 figure) and support for 8TB SATA disks which are expected to become available later this year.

DAG 2.0
Well, sort of. Exchange 2013 adds functionality to the Database Availability Groups. To enhance site resiliency, servers can be in different locations, meaning you you aren’t required to place CAS servers in the Active Directory site together with the Mailbox servers. This creates interesting scenarios, where for example you could create (centralized) CAS farms (even in dedicated sites), while the DAGs are hosted in other sites. Major benefit of this is also that this reduces the namespaces required to create a resilient Exchange configuration.

Certificates
Client Access servers deal with certificate management; Mailbox servers contain self-signed certificates which are automatically trusted. The EAC contains a notification center which will report on certificates nearing expiration.

Data Loss Prevention
Here, Data Loss doesn’t refer to loss of bits, but to loss of sensitive information. Exchange 2013 provides a mechanism to protect sensitive data. Supported clients, like Outlook 2013, provide notifications of possible policy breaches through PolicyTips, much like MailTips. More information on DLP here.

OWA 2013
Outlook Web App (OWA) in Exchange 2013 adds integrated apps, like Bing Maps. Apps can be managed using the EAC. Apps installed in Outlook 2013 also become available in OWA 2013 and vice versa. OWA 2013 also offers LinkedIn integration and merged calendar view (like in Outlook).

OWA 2013 supports the following browsers when compared to OWA 2010:

  • Windows
    • Internet Explorer 7 or later (same);
    • Firefox 12 or later (was Firefox 3.0.1+);
    • Chrome 18 or later (was Chrome 3.0.195.27+);
    • Safari 5.1 or later.
  • Mac
    • Firefox 12 or later (was 3.0.1+);
    • Safari 5.0.6 or later (was 3.1+);
    • Chrome 18 or later.
  • Linux
    • Firefox 12 or later (was 3.0.1+);
    • Chrome 18 or later.
  • Tablets & Smartphones
    • Windows 8 PRE;
    • iOS 5.0 or later for iPhone or iPad;
    • Android 4.0 or later;
    • Other browsers revert to Light mode

Note: iPad 1 has 256 MB, OWA 2013 requires 512 MB therefor it isn’t supported on iPad1 devices.

When using compatible browsers OWA 2013 supports offline mode, which means you can read or compose messages while disconnected, using your system to store the information. More information on which platform / browser combinations supports offline mode can be found here.

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eDiscovery
Recently, Microsoft announced it was no longer required to have an Enterprise CAL to perform Multi-Mailbox Searches in Exchange 2010. Like some predicted this was a clue on changes in Exchange 2013, which not only allows for cross-platform against Exchange, Lync and Sharepoint (In-Place eDiscovery), but allows you to export mail contents to PST files.

You can also search across primary and archive mailboxes in OWA.

Compliance
Also, Legal Hold, now known as In-Place Hold, can now be performed based on queries and can be bound to a certain timeframe as well in Exchange 2013.

Unified Messaging
In Exchange 2013, UM functionality is split between CAS and Mailbox servers which explains the absence of the UM server role. The CAS server deals with call routing, while the Mailbox server provides UM services like synthesis.

Based on UCMA 4.0, Exchange 2013 UM utilizes the same engine for text-to-speech (TTS) and automatic speech recognition (ASR). The generated grammar files, previously generated and stored per server, are generated by the Mailbox Assistant running on the Mailbox server hosting the arbitration mailbox. The speech grammar files are stored in the arbitration mailbox and can be downloaded by Mailbox servers.

When trying to resolve the Caller ID, Exchange 2013 UM will consult different sources besides the default contacts folder, like other contact folders and social networks.

Updated MRS
The Mailbox Replication Service (MRS) has been updated in Exchange 2013 to enable bigger parallel moves, providing progress reports using notifications and to make the process more resilient by automatic retries and move priorization.

Site Mailboxes
Exchange 2013 introduces a new concept called Site Mailboxes, which bind an Exchange mailbox to a Sharepoint site. Goal is to enable users to collaborate easier, by enabling site members to utilize a single interface to access documents as well as related messages. More information on Site Mailboxes here.

PowerShell 3.0
The Exchange Management Shell is now based on WinRM 3.0.

Miscellaneous
Other changes worth mentioning:

    • Lync 2013 can archive contents in Exchange 2013 and use it to store contacts;
    • Exchange Workload Management, more information here.
    • To skip the license screen during (unattended) setups, you can use the switch IAcceptExchangeServerLicenseTerms with setup.exe, e.g.
      Setup /m:Install /r:C,M /OrganizationName:X /IAcceptExchangeServerLicenseTerms

Exchange 2013 Preview: Prerequisites

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Note: This article is based on a pre-release product and may therefor be subject to changes.

Yesterday, the Exchange team released the preview (you can also call this a public beta) of Microsoft Exchange Server 2013. The build version of the Exchange 2013 Preview is 15.0.466.10.

You can download the 1,5GB self-extracting Exchange 2013 Preview here.

Prior to installing Exchange 2013 preview, you need to install the following prerequisites depending on the targeted platform

Note: Clicking the checkmark leads to the download.

Component

Windows Server
2008 R2 SP1

Windows Server
2012
.NET Framework 4.5 RC

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Windows Management Framework 3.0 RC

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UCMA 4.0 Preview

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Office 2010 Filter Pack (Mbx)

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Office 2010 Filter Pack SP1 (Mbx)

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Windows Identity Foundation (KB974405)

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KB2619234

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KB2533623

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Note: When present, uninstall the Visual C++ 11 Beta Redistributable after installing the UCMA component. On Windows Server 2008 R2 SP1 you also need to register ASP.NET after uninstalling the VC++ 11 Beta Redistributable, before installing Exchange 2013, using:
%SystemDrive%\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -ir -enable
followed by an IISReset.

Required Windows Features
These cmdlets install the required Windows features:

Cmdlets

Windows Server
2008 R2 SP1

Windows Server
2012
CAS Import-Module ServerManager;
Install-WindowsFeature RSAT-ADDS;
Install-WindowsFeature Desktop-Experience, NET-Framework, NET-HTTP-Activation, RPC-over-HTTP-proxy, RSAT-Clustering, RSAT-Web-Server, WAS-Process-Model, Web-Asp-Net, Web-Basic-Auth, Web-Client-Auth, Web-Digest-Auth, Web-Dir-Browsing, Web-Dyn-Compression, Web-Http		 Add-WindowsFeature RSAT-ADDS;
Add-WindowsFeature AS-HTTP-Activation, Desktop-Experience, NET-Framework-45-Features, RPC-over-HTTP-proxy, RSAT-Clustering, Web-Mgmt-Console, WAS-Process-Model, Web-Asp-Net45, Web-Basic-Auth, Web-Client-Auth, Web-Digest-Auth, Web-Dir-Browsing, Web-Dyn-Compression, Web-Http-Errors, Web-Http-Logging, Web-Http-Redirect, Web-Http-Tracing, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Lgcy-Mgmt-Console, Web-Metabase, Web-Mgmt-Console, Web-Mgmt-Service, Web-Net-Ext45, Web-Request-Monitor, Web-Server, Web-Stat-Compression, Web-Static-Content, Web-Windows-Auth, Web-WMI, Windows-Identity-Foundation
MBX or CAS/MBX Import-Module ServerManager;
Install-WindowsFeature RSAT-ADDS;
Install-WindowsFeature Desktop-Experience, NET-Framework, NET-HTTP-Activation, RPC-over-HTTP-proxy, RSAT-Clustering, RSAT-Web-Server, WAS-Process-Model, Web-Asp-Net, Web-Basic-Auth, Web-Client-Auth, Web-Digest-Auth, Web-Dir-Browsing, Web-Dyn-Compression, Web-Http-Errors, Web-Http-Logging, Web-Http-Redirect, Web-Http-Tracing, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Lgcy-Mgmt-Console, Web-Metabase, Web-Mgmt-Console, Web-Mgmt-Service, Web-Net-Ext, Web-Request-Monitor, Web-Server, Web-Stat-Compression, Web-Static-Content, Web-Windows-Auth, Web-WMI		 Add-WindowsFeature RSAT-ADDS;
Add-WindowsFeature AS-HTTP-Activation, Desktop-Experience, NET-Framework-45-Features, RPC-over-HTTP-proxy, RSAT-Clustering, Web-Mgmt-Console, WAS-Process-Model, Web-Asp-Net45, Web-Basic-Auth, Web-Client-Auth, Web-Digest-Auth, Web-Dir-Browsing, Web-Dyn-Compression, Web-Http-Errors, Web-Http-Logging, Web-Http-Redirect, Web-Http-Tracing, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Lgcy-Mgmt-Console, Web-Metabase, Web-Mgmt-Console, Web-Mgmt-Service, Web-Net-Ext45, Web-Request-Monitor, Web-Server, Web-Stat-Compression, Web-Static-Content, Web-Windows-Auth, Web-WMI, Windows-Identity-Foundation

Firewall
On Windows Server 2012, create an inbound firewall rule for port 139 when installing Client Access server.

Active Directory Requirements
Be advised that a minimum of 1 Windows Server 2008 Domain Controller and Global Catalog server is required in each site where you want to install Exchange 2013 Preview. Windows Server 2003 Forest Level is supported.

After successfully preparing Active Directory for Exchange 2013, the schema version will be 15132, Forest version 15448 and the Domain version 13236. More information on how to verify those values here.

To quickly check the level of your domain controllers, you can use the script provided here which will report the msDS-Behavior-Version attribute (3 = 2008).

Order of things
Microsoft recommends you install Mailbox servers before installing Client Access servers.

IPv6
Like Exchange 2010, Exchange 2013 supports IPv6. However, a pure IPv6 environment isn’t supported, so IPv4 is still required.

Co-Existence
Everybody who’s still running on Exchange 2003 (many customers are) need to follow an intermediate upgrade path when moving to Exchange 2013 when it goes RTM, as co-existence between Exchange 2013 and Exchange Server 2003 isn’t supported. Note that the preview version isn’t supported in co-existence with any Exchange version by the way.

Release Notes
Be sure to also check out the Release Notes here.