Cisco Unified Communications Manager (CUCM) Video #2: Region

Topics What is CUCM Region? Brief introduction to Codecs Common Codecs – G.711, G.729 and iLBC Region Configuration Steps

CUCM Region Defines the maximum bit rate between group of IP Phones. Codecs that have higher bit rate than the value set in Region will not be used between IP Phones. Region is used to for bandwidth sizing. Codecs will determine how many calls are possible for a given bandwidth.

Codecs The word CODEC is taken from the words COder and DECoder. Codecs are used for compression and decompression of audio signals. Not all audio codecs can be used for telephony. IP Phones need to have the same Codec to play the audio stream both ways. If IP Phones don’t have the same type of codec a Transcoder is required. Traditional Transcoding: G.711 <-> Other Universal Transcoding : Other <-> Other Some codecs are not free to use. Most common codecs for telephony are already available in the Cisco IP Phones.

Common Codecs Codec Information Bandwidth Calculations Codec & Bit Rate (Kbps) Codec Sample Size (Bytes) Codec Sample Interval (ms) Mean Opinion Score (MOS) Voice Payload Size (Bytes) Voice Payload Size (ms) Packets Per Second (PPS) Bandwidth MP or FRF.12 (Kbps) Bandwidth w/cRTP MP or FRF.12 (Kbps) Bandwidth Ethernet (Kbps) G.711 (64 Kbps) 80 Bytes 10 ms 4.1 160 Bytes 20 ms 50 82.8 Kbps 67.6 Kbps 87.2 Kbps G.729 (8 Kbps) 10 Bytes 3.92 20 Bytes 26.8 Kbps 11.6 Kbps 31.2 Kbps G.723.1 (6.3 Kbps) 24 Bytes 30 ms 3.9 33.3 18.9 Kbps 8.8 Kbps 21.9 Kbps G.723.1 (5.3 Kbps) 3.8 17.9 Kbps 7.7 Kbps 20.8 Kbps G.726 (32 Kbps) 5 ms 3.85 50.8 Kbps 35.6 Kbps 55.2 Kbps G.726 (24 Kbps) 15 Bytes   60 Bytes 42.8 Kbps 27.6 Kbps 47.2 Kbps G.728 (16 Kbps) 3.61 28.5 Kbps 18.4 Kbps 31.5 Kbps G722_64k(64 Kbps) 4.13 67.6Kbps ilbc_mode_20(15.2Kbps) 38 Bytes NA 34.0Kbps 18.8 Kbps 38.4Kbps ilbc_mode_30(13.33Kbps) 50 Bytes 25.867 Kbps 15.73Kbps 28.8 Kbps

G.711 ITU-T standard. Used in the PSTN (Public Switched Telephony Network and most IP PBX implementations. Comes in two variants – u-law and a-law. U-law is commonly used in the United States, North America and Japan. A-law is used anywhere else. Medium complexity codec – uses less computational resources.

G.729 Mostly used in VOIP applications due to low bandwidth requirements. Commonly used for calls outside the IP LAN environment. Good for Latin Based language but not fit for music on hold. Has several two main variants of the original – G.729a and G.729b. G.729a, medium complexity G.729b, added VAD (Voice Activity Detection).

iLBC Internet Low Bitrate Codec – released in 2004. Was used in Yahoo Messenger, Gtalk and older versions of Skype. Royalty free – no need to pay to use.

Region Configuration Specify Region Name. Modify Relationship to Other Regions. Set Max Audio Bit Rate Set Max Video Call Bit Rate Set Link Loss Type “Use System Default” will follow the values set in Service Parameter Configuration -> Cisco Call Manager.