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Cisco IOS XE Integrated Session Border Controller Configuration Guide for the Cisco ASR 1000 Series Aggregation Services Routers
OL-15421-01
Chapter 7 H.248 Services—Signaling and Control
Flexible Address Prefix Provisioning
• Partial wildcards which omit one or more tiers of the termination name are not supported. For
example, “operator/sip/*” is not supported, but “operator/sip/*/*/*/*/*/*/*” is. The exception is the
full wildcard, which is simply “*”.
• You can construct transactions with multiple overlapping wildcarded commands, and when a single
transaction contains multiple commands referencing the same terminations, the commands operate
in order. However, when a termination is subtracted, any other commands affecting it are ignored.
For example, suppose a media gateway (MG) has a single termination a/b/1. The following are
examples of overlapping wildcarded commands and their returns:
–
“audit value a/*/*, audit value */b/*” returns a/b/1 in the response twice.
–
“modify a/*/*, modify */b/*” modifies termination a/b/1, with the second modify overwriting
the first, and return success to both commands.
–
“subtract a/*/*, subtract */b/*” subtracts a/b/1 as part of the first subtract and ignores the second
subtract.
–
“subtract a/*/*, modify */b/*” subtracts termination a/b/1 and ignores the modify.
–
“modify a/*/*, subtract */b/*” does the same as above.
When a wildcard command is ignored under these circumstances, the response to that command is
error 431 “No Termination ID matched a wildcard.”
When a non-wildcarded command is ignored, the response is error 430 “Unknown Termination ID.”
Flexible Address Prefix Provisioning
When the Remote Source Address Mask (rsam) property of the ETSI TS 102 333 Gate Management
(GM) package is not involved in the flow entry hash key construction, there are no limits to the network
mask length, because the mask specific to each flow is used to validate the SBC packets after the flow
entry is retrieved (that is, the expected gm/rsam information is obtained from the flow entry that is stored
during the signaling/call setup process). However, when features such as
Local Source Properties
(Address and Port) or Remote Source Address Mask Filtering are used, where flows from various source
IPs can connect to the same service destination IP address and port, the source IP network mask
(gm/rsam network mask) must be used in the hash key construction in addition to the destination IP and
port in order to identify and retrieve a unique flow entry.
Because there is no way to know about the existence of the multiple terminations when the data border
element (DBE) tries to construct the hash key for retrieving the flow entry, support has been added for
the Flexible Address Prefix Provisioning feature. This feature creates a dummy entry using the service
IP and port to construct a hash key when the first termination with this service IP and port combination
is established. This dummy entry is shared among all the terminations sharing the same service IP and
port for storing network masks, and supports three different lengths of network masks on a given shared
address at one time or different shared addresses. Any length of network masks is allowed.
This feature is applicable to both IPv4 and IPv6 flows.
If there is only one network mask in a dummy entry, the DBE uses this network mask to mask out the
source IP of the incoming packet and, together with the destination IP/port, constructs a new hash key
to locate the corresponding termination flow entry from the flow table.
If multiple network masks are configured in the dummy entry, the DBE masks the source IP of the
incoming packets using the multiple network masks stored in the dummy entry sequentially from longest
to shortest. If a flow entry is located, then the DBE stops the flow retrieval operation and continues the
rest of SBC processing. When a termination is subtracted, its network mask length is removed from the
dummy entry if the termination is the last one with that gm/sam network mask length.