Streaming Media Supplement sa2150 and sa2250

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Chapter 4 Understanding Media-IXT and WMT
o If there is no match, the child Media-IXT makes a new tunnel to the parent Media-IXT which acts like
the WMT origin server for the given pathname. In doing this, the child Media-IXT passes the
information it extracted from the URL within the WMT metafile on to the parent Media-IXT. So, the
parent Media-IXT has the means to repeat the process:
8. The parent Media-IXT checks its internal table of connections to unique paths on WMT origin servers,
called tunnels.
o If there is no match, the parent Media-IXT makes a new tunnel to the origin server host for the given
pathname.
o If there is a match, the parent Media-IXT simply attaches the child Media-IXT to the appropriate tunnel.
As far as the parent Media-IXT is concerned, the child Media-IXT is the same as a browser client.
9. The client sends a request to start playing the content; the request travels the tunnel from the child Media-
IXT to the parent Media-IXT, which sends content back to the client via the child Media-IXT within 5
seconds.
10. At some point, the client sends a request to stop playing the content; the request travels the tunnel from the
child Media-IXT to the parent Media-IXT, which detaches the child Media-IXT from the tunnel, and
content stops streaming within 5 seconds.
11. On client disconnect, if no other clients are connected to the origin server, each Media-IXT tears down the
upstream connection and removes the tunnel from the tunnel table.
Understanding clustering and WMT
Media-IXT supports management-only clustering, not full clustering. See “Understanding clustering” on
page 15.
Understanding VIP failover and WMT
VIP failover is a Media-IXT clustering feature. For WMT, an explicit, management-only cluster is the only
supported deployment for VIP failover.
In a Media-IXT cluster, a pool of virtual IP addresses is assigned to the nodes in the cluster. When one node
fails, other nodes must take over the traffic going to the down node’s virtual IP addresses.
The node with the lowest IP address can assign another node to take over the traffic that would normally go to
the down node. This technique is called VIP failover (the VIP stands for Virtual IP address). The failover may
not complete quickly enough to avoid adding latency to client requests.
Media-IXT’s VIP failover capability for Windows Media Technologies is built in. (The binary used for
RealNetworks VIP failover, mixt_vip_config, is not involved.)
Media-IXT rewrites the URLs in the WMT metafile to contain the IP address of the Media-IXT interface on
which the HTTP request arrived. This is compatible with the way VIP failover works.
Understanding CDS preload and WMT
Media-IXT 4.x does not support CDS preload of WMT content.
NOTE There may be a maximum of one upstream connection to another Media-IXT or WMT
origin server per Media-IXT node in a Media-IXT cluster. This is because in a Media-
IXT cluster, there is no knowledge of which hosts in the cluster currently have active
live splitting connections to upstream servers.