75
FLASH
MEDIA
SERVER
4.5
CONFIGURATION
AND
ADMINISTRATION
Configuring the server
Last updated 11/28/2012
Configuring Differentiated Services (DiffServ)
Flash Media Server 3.5.2
Understanding DiffServ
Use Differentiated Services to handle different types of traffic differently within a network. For example, you could give
RTMP traffic a higher priority than FTP traffic. Or, you could give higher bandwidth and latency to RTMP than to
HTTP. A publisher could choose to give paying customers' streams higher priority. A CDN or other hosting company
could choose to give higher-paying publishers' streams higher priority.Historically, IP contained a feature called Type
of Service (TOS) (see RFC 1349). Each packet's header contained a 3-bit Precedence value and three 1-bit flags. You
could use these bits to prioritize packets in an operating system kernel or router. IPv6 had an experimental (and now
deprecated) feature that provided for a 3-bit Priority, sent in the same header position as TOS precedence. This feature
was replaced by a TCLASS (later renamed TRAFFIC_CLASS) byte that works the same as IP_TOS in
IPv4.Differentiated Services (see RFC 2474) has replaced TOS with a single 6-bit value called DSCP (Differentiated
Services Code Point). In IPv6, the TCLASS octet has been renamed the DS octet, and the other 2 bits are reserved. In
IPv4, the TOS byte no longer has a name, and the other 2 bits are used for ECN (Explicit Congestion Notification).Edge
routers and endpoints can make decisions on a per-flow basis. They mark the packets within the flow so that internal
routers can look at the headers (as with TOS). DiffServ is defined such that edge routers can work entirely based on
service-level agreements (SLAs) between two networks, but internal sources can also mark packets based on the type
of service required for internal traffic.
DiffServ system requirements
Differentiated Services is supported on Linux only.There is no standard way of setting the bits on Windows platform
that would work on all versions of the operating system that Flash Media Server supports. For more information on
setting Differentiated Services bits on Windows, see the following,
http://support.microsoft.com/kb/248611
.If you try
to set the bits on Windows, the following message prints to the Authorization log, “Setting Diff Serv bits is not
supported for Windows Platforms”.
DiffServ Internet Protocol versions
The Flash Media Server Differentiated Services feature supports the IPv4 protocol only. Setting the bits for IPv4
protocol means setting the Differentiated Services field (previously called the Type of Service field) of the IP packet
header. The following is an IPv4 packet header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+