GigaSMART SIP/RTP Correlation

The CallerID is tied to the Call-ID and remains constant for the duration of the session:

CallerID (A) <-----(Call-ID)-----> CalleeID (B)

CallerID tracking is based on the initial caller (A) and does not change until the Call-ID changes. Even if the callee, (B), sends a new INVITE during the SIP session, if that INVITE uses the same Call-ID, then the CallerID information in the SIP session display will still identify the initial caller, (A); it will not switch to reflect that (B) is now the caller.

SIP/RTP correlation handles all SIP signaling and RTP/RTCP traffic, including RTCP control traffic, as well as that belonging to a call session.

The following is supported:

When a packet containing SIP, RTP, or RTCP traffic is received, the SIP/RTP correlation engine looks up the session in the session table for load balancing ports and sampling maps or whitelist map. All SIP/RTP traffic with port or load balancing port group is forwarded based on the session table. The correlation engine load balancing keeps track of both the SIP session and the associated multiple RTP channels.

Each session identifies both sides of media streams (RTP) associated with the session. The SIP session has an aging timer that is configurable.

When a session matches one of the configured flow sampling rules, it is either accepted for sampling or rejected. If it is accepted, all packets belonging to that session are sent to the tool port. Otherwise, all packets belonging to the session are dropped.

To configure SIP/RTP Load balancing, follow these steps:

RTP traffic will be sampled and sent to the maps with the rules that match. RTP non-correlated traffic will be sent to the collector.

Only one SIP interface type is supported per engine, for example, S5. There is no mixing of interface types, such as S5 GTP-U with SGi.

The SIP whitelist contains caller IDs, callee ID, the range for caller IDs, the range for callee IDs and the IP address. Each forward list entry in a file is a SIP caller ID, callee ID, caller ID range, callee ID range or IP address. The forward list can contain all types of entries.

forward list entries can be alphabetic, IP address, and numeric. For each entry, specify up to 64 alphanumeric characters. Some special characters are also supported.

You can manually add one entry at a time to a whitelist file, or you can upload files in.txt format. You must provide the whitelist caller ID range in numeric. You can also provide multipile entries to the forward list by ID range configuration. Each whitelist file can have up to 20,000 entries. One or more whitelist files can be fetched from a local directory or remote URL using HTTP or SCP.

On GigaVUE‑HC2 nodes, the forward list database supports 500,000 entries. On GigaVUE‑HC3 nodes, the forward list database supports 1 million entries.

Multiple forward list databases can reside on a GigaVUE node, but only one forward list is applied to a GigaSMART group at a time.

Only one whitelist map is supported for a GigaSMART group. The GigaSMART operation does not have any rules for forward listing.

FlowVUE is used for session-aware (stateful) load balancing and forward listing with sampling. Only RTP traffic will be sampled. There is no sampling of SIP traffic.

Up to five flow sample maps per GigaSMART group are supported. Each flow sample map can have 20 rules. Use rules to filter on caller ID. The rules support both alphabetic and numeric characters, up to 64 characters. Some special characters are also supported, such as wildcard characters.

Sampling is based on caller ID only (the from field).

The number of supported SIP and RTP sessions are as follows:

Each SIP session can handle two RTP streams in both directions (bidirectional).

The number of supported TCP sessions are as follows:

SIP is a text-based protocol, which is supported over UDP and TCP. The size of the

SIP message can vary greatly, so fragmentation and segmentation are common and are supported for tunneled SIP and non-tunneled SIP (IMS).

IPv4 and IPv6 are supported as follows:

The following is not supported:

SIP Common Presence and Instant Messaging (CPIM) content masking is supported, but only when the SIP transport is UDP.

The SIP method, MESSAGE, carried over UDP, might contain user-friendly, readable text messages. Use masking to replace these messages with x’s, so they cannot be read.

Note:  SIP/RTP correlation cannot mask text messages with a content type other than message/CPIM”, such as plain text.

The following are behaviors for some particular SIP methods:

Note:  SIP TCP packets with parse errors are not sent to collector. SIP TCP packets will be sent to the tool and incremented as parse errors in the session table stats.

The forward list (all whitelist files) reside on the leader of the cluster. The member nodes receive a copy of the forward list from the leader. Updates to the forward list are synchronized from the leader to the non-leaders. If a member node leaves the cluster and rejoins, its forward list will be resynchronized.

Use the cluster leader preference command to specify the highest preference for the leader, the second highest preference for the standby node, and lower preferences for the normal nodes in the cluster.

If there are GigaVUE TA Series nodes in the cluster, they will not receive a copy of the forward list.

GigaSMART SIP Correlation engine correlates NAT/PAT enabled SIP/RTP packets. The correlation engine compares the top most "Via" address and the contact address of the device with the Layer 3 network address to find whether the device is configured with NAT.

To enable the NAT support, from the device view:

The following list is not currently supported by SIP/RTP correlation:

Note:  SIP/RTP correlation and GTP correlation are not supported on the same GigaSMART engine port.

To display SIP report, do the following:

Map Statistics displays the counts sessions that matched a particular map.

For SIP Flow Sample maps, the counters show how many sessions matched the Caller-ID rule and were either accepted or rejected based on the sampling percentage.

For SIP Whitelist maps, the counter shows how many total entries are in the Whitelist and how many sessions matched those entries. .

To display SIP Map Statistics, do the following:

■

On the left navigation pane, click from Traffic select Maps> Statistics. The Statistics page displays a count of the rules that actually matched in a map.

GigaSMART supports sampling/scaling based on fixed percentages, which remain in effect at all times, regardless of the tool port utilization. However, tool utilization may not be as efficient as not using fixed percentage for every use case. Staring with GigaSMART version 5.4 support for throttling sessions based on the traffic (pps) reaching a tool port is available. This feature helps avoid packets being drops during peak times by allowing users to adjust throttling start and stop levels.

The illustration below is a configuration and Intra Flow for Tool Port Throttling.

Each SIP session comes with RTP streams and each of the RTP stream uses a specific codec for information transfer. We can use this codec information to our advantage and do predictive analysis on how much pps would be generated for a given SIP session.

Based on the outcome of the pps for a given RTP stream codec, admission control module will check this value against the cumulative packet throughput on the destination tool-port to decide if the session will be Accepted or Rejected.

Example: Tool port 1/1/x1 is configured with a threshold of 3k pps.

1/1/x1

0

0

3000

1/1/x1

1

500

500

3000

Yes

1/1/x1

2

1500

2000

3000

Yes

1/1/x1

3

800

2800

3000

Yes

1/1/x1

4

500

3300

3000

No

In software version 5.4 Tool port throttling applies only to SIP sessions for audio and only load balanced ports are supported in tool port throttling. Use case where there are tapping multiple interfaces using multiple engines, one SIP session can be throttled in one engine and not in another.