Key Point - Forking is critical to advanced SIP features such as "find-me follow-me." Critical to this process is ringing to let the caller alert the callee or (called party) of the call. In traditional PSTN-Public Switched Telephone Network communications "early media" refers to ringing and announcements to indicate the status of the call - ringing, busy, fast busy, call redirection, status "you have 12 callers ahead of you." In SIP, the forking process provides "early media" sending specialized ring-tones, audio announcements (e.g. call center status announcements), images or video before SIP session is accepted. However, there is NO common means of providing signaling to the receiver because of different types of hardware, softphones, UI-user interfaces, ringing devices and many other factors. In addition, early media may be onmidirectional or sequential forking, bidirectional or parallel-dual forking.

Early media failures can occur when the callee picks up and the UAS sends a 200 (OK) response with an answer, in parallel with the first media packets. If the first "early media" packets are received by the caller - UAC-User Agent Client, "media clipping (at the beginning of the media sequence)" or "media dipping" (at the end of the media sequence) can occur. This can occur is that the UAC cannot send media until the 200 (OK) response from the UAS arrives. Causes for clipping can be manyfold, however, UAC signaling, packet arrival delays), bandwidth, different SIP "methods" and commands between SIP systems and other factors. In addition, SIP signaling can typically take a different routing path than the media (communications) transmission which can be one of the factors causing media clipping.

"Late media" announcements (such as "will you take a survey" or (click for special offer") occur after the BYE and may have the same problems. Details can be found by reading RFC 3260.
In summary, incompatibility between SIP systems can result in communications chaos.

RCC-Remote Call Control also known as third-party call control is provided by CSTA-Computer Supported Telephony Applications. CSTA was developed by the European Computer Manufacturers Association (ECMA) and subsequently was formally standardized by the ITU-T, incorporating the Switch-to-Computer Applications Interface (SCAI).

CSTA is an OSI protocol stack that provides an open system interface to a PBX-Private Branch eXchange, ACD-Automatic Call Distributor or CO-Centrex central office switching. CSTA uses, among other technologies, SALT-Speech Application Language Tags specification and its SMEX-Simple Messaging Exchange element, telephony call control capabilities in MSS-Microsoft Speech Server to allow a developer to create sophisticated telephony-based speech applications that can exploit both basic call control services such as ANI-Automatic Number Identification (caller ID) and DNIS-Dialed Number Identification Service (800), using the included basic call controls, or extended call control services, to create custom call controls.

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The animated presentation can be found at: http://www.techtionary.com/podcasts/vpls/

I originally wrote about VPLS sometime ago. I was prompted to update the information with an announcement from Verizon (see below). In addition, I wanted to remind network planners to have both redundant (multiple) and diverse (separate cable routes and trenches) both wireless and wireline services.

CIO Version - Here is the translation of those acronyms into "no-tech" English. Virtual Private LAN Service allows customers to create VLANs-Virtual Local Area Networks in a metro network or global network using IP-Internet Protocol MPLS-Multi-Protocol Label Switching or VPNS-Virtual Private Network Service. In CEO talk, this means you can connect all the branches in the same city without costing a lot and cities elsewhere "almost" as easily. In the animated presentation, you will see the differences between VPLS and VPNS. There are many others including training, availability, diversity, DR-Disaster recovery, application such as hub-spoke versus mesh networking and others. Check with your provider as YMMV-your mileage may vary.

CTO Version - LAN switching is a Layer 2 (Datalink) concept of switching rather than routing which takes place at Layer 3 (Network). In LAN switching all packets are "flooded" to all locations until they find their destination. Nice idea if you have only a few sites. Originally known as TLS-Transparent LAN-local Area Network Service, Metro-Ethernet, Ethernet Private Line and now often called VPLS-Virtual Private LAN Service, here are some reasons why you should consider this service.
First, it is easy-to-implement with plug-and-play installation.
Next, LAN Switches are cheap.
Third, VPLS provides very flexible BOD-bandwidth on demand options.
Fourth, it is a great solution for same-city customers with many locations.
Here are some reasons against: First, it doesn't grow or scale well to tens of sites and hundreds of users. Second, faster bandwidth doesn't provide QoS or solve flooding of packets due to large applications.

In Layer 3 routing, only the packets that are destined for the other location are sent. That is, packets are routed based on the destination IP address.
Here are some reasons for routing: First, it scales or grows essentially infinitely for customers with domestic and global locations.
Second, routing supports all kinds of IT systems new or legacy.
Third routing provides higher security.
Reasons against routing: First, there is a high cost with routing and routing will always be more expensive than switching.
Second, routing is complex to manage.
Third, routing requires very knowledgeable and technical staff.

I didn't forget VPLS, just needed a minute to get through the basics. VPLS uses MPLS to provide the "seamless" connections for VPLS. Shown in the presentation is the IP-Internet Protocol packet before and with the MPLS "label" attached or "tagged" on as it was originally called. MPLS consists of four elements, label bits, experimental bits, a stack bit and TTL-Time-To-Live bits which indicate the number of Label Switch Routers passed. Shown here is the "multi-protocol" part of MPLS and how it works with the other major networking protocols such as ATM, Frame Relay, Ethernet and others.

As shown in the presentation MPLS is used to connect locations and VLANS together.
In the next slide are the three key access topologies - ethernet-line for two sites, ethernet-LAN for three or more sites and ethernet-access for VPN/internet. This makes implementation and configuration of VLANS really simple.

WHY VPLS - Summary Here are a few business reasons: - Extends LAN infrastructure easily - Expands metro-net to global-net - Migrates Frame Relay to MPLS - Utilizes "pseudowire" approach - Needs "mesh" connections - Connect call centers via SIP - Provide DR-Disaster Recovery for data centers - Seeks greater customer (less carrier) control - Has multi- and broadcast traffic - Building a CDN-Content Delivery Net - Building an overlay multi-carrier network.

VPLS-Virtual Private LAN Service is going to be a great solution for any customer with more than location.

Here's Verizon's Information - Verizon Business Takes Virtual Private LAN Service Global
The following was provided by Verizon - "With this global expansion, the reach of Verizon VPLS will extend beyond the U.S. to customers in 31 international locations, including the United Kingdom, France, Germany, India, Australia, Canada, Hong Kong, Singapore and South Korea. Verizon Business leverages its extensive network of interconnection agreements with other in-region Ethernet providers to offer this expansive coverage.
Verizon VPLS, an advanced MPLS-based layer 2 virtual private network delivered via Verizon Business' innovative global-provisioning Ethernet platform, is ideal for organizations seeking to link multiple sites in a flexible, operationally efficient model. VPLS is protocol-independent, supporting both IP and non-IP applications, which allows customers to retain complete control of their own routing. In addition, VPLS allows customers to access Verizon's extensive portfolio of Ethernet services and other data networking services offered by the company.
In a challenging economy, Verizon Business' global expansion of VPLS service and growth of its Ethernet portfolio is a good-news story," said Stan Hubbard, senior analyst with Heavy Reading. The company's global provisioning platform for enabling a seamless experience, long history delivering Ethernet services, broad portfolio and stability will certainly all appeal to multinational customers.
VPLS is an optimal platform for converged networking as it allows for prioritization of applications via multiple classes of services (CoS). An organization can customize prioritization to ensure that business-critical applications receive the highest priority across the network. Verizon Real-time CoS, for example, makes VPLS ideal for carrying latency-sensitive traffic such as voice-over-IP (VoIP) and digital video. VPLS also enables customers to provision their network bandwidth from 1 megabit per second to gigabit per second and beyond, enabling efficient and cost-effective transmission of voice and data traffic. And VPLS is backed by robust service level agreements (SLAs), which customers expect from a carrier-class wide area network service." END - There was no direct link in the Verizon Press Release for more information.

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The animated presentation can be found at: http://www.techtionary.com/podcasts/vpls/

I originally wrote about VPLS sometime ago. I was prompted to update the information with an announcement from Verizon (see below). In addition, I wanted to remind network planners to have both redundant (multiple) and diverse (separate cable routes and trenches) both wireless and wireline services.

CIO Version - Here is the translation of those acronyms into "no-tech" English. Virtual Private LAN Service allows customers to create VLANs-Virtual Local Area Networks in a metro network or global network using IP-Internet Protocol MPLS-Multi-Protocol Label Switching or VPNS-Virtual Private Network Service. In CEO talk, this means you can connect all the branches in the same city without costing a lot and cities elsewhere "almost" as easily. In the animated presentation, you will see the differences between VPLS and VPNS. There are many others including training, availability, diversity, DR-Disaster recovery, application such as hub-spoke versus mesh networking and others. Check with your provider as YMMV-your mileage may vary.

CTO Version - LAN switching is a Layer 2 (Datalink) concept of switching rather than routing which takes place at Layer 3 (Network). In LAN switching all packets are "flooded" to all locations until they find their destination. Nice idea if you have only a few sites. Originally known as TLS-Transparent LAN-local Area Network Service, Metro-Ethernet, Ethernet Private Line and now often called VPLS-Virtual Private LAN Service, here are some reasons why you should consider this service.
First, it is easy-to-implement with plug-and-play installation.
Next, LAN Switches are cheap.
Third, VPLS provides very flexible BOD-bandwidth on demand options.
Fourth, it is a great solution for same-city customers with many locations.
Here are some reasons against: First, it doesn't grow or scale well to tens of sites and hundreds of users. Second, faster bandwidth doesn't provide QoS or solve flooding of packets due to large applications.

In Layer 3 routing, only the packets that are destined for the other location are sent. That is, packets are routed based on the destination IP address.
Here are some reasons for routing: First, it scales or grows essentially infinitely for customers with domestic and global locations.
Second, routing supports all kinds of IT systems new or legacy.
Third routing provides higher security.
Reasons against routing: First, there is a high cost with routing and routing will always be more expensive than switching.
Second, routing is complex to manage.
Third, routing requires very knowledgeable and technical staff.

I didn't forget VPLS, just needed a minute to get through the basics. VPLS uses MPLS to provide the "seamless" connections for VPLS. Shown in the presentation is the IP-Internet Protocol packet before and with the MPLS "label" attached or "tagged" on as it was originally called. MPLS consists of four elements, label bits, experimental bits, a stack bit and TTL-Time-To-Live bits which indicate the number of Label Switch Routers passed. Shown here is the "multi-protocol" part of MPLS and how it works with the other major networking protocols such as ATM, Frame Relay, Ethernet and others.

As shown in the presentation MPLS is used to connect locations and VLANS together.
In the next slide are the three key access topologies - ethernet-line for two sites, ethernet-LAN for three or more sites and ethernet-access for VPN/internet. This makes implementation and configuration of VLANS really simple.

WHY VPLS - Summary Here are a few business reasons: - Extends LAN infrastructure easily - Expands metro-net to global-net - Migrates Frame Relay to MPLS - Utilizes "pseudowire" approach - Needs "mesh" connections - Connect call centers via SIP - Provide DR-Disaster Recovery for data centers - Seeks greater customer (less carrier) control - Has multi- and broadcast traffic - Building a CDN-Content Delivery Net - Building an overlay multi-carrier network.

VPLS-Virtual Private LAN Service is going to be a great solution for any customer with more than location.

Here's Verizon's Information - Verizon Business Takes Virtual Private LAN Service Global
The following was provided by Verizon - "With this global expansion, the reach of Verizon VPLS will extend beyond the U.S. to customers in 31 international locations, including the United Kingdom, France, Germany, India, Australia, Canada, Hong Kong, Singapore and South Korea. Verizon Business leverages its extensive network of interconnection agreements with other in-region Ethernet providers to offer this expansive coverage.
Verizon VPLS, an advanced MPLS-based layer 2 virtual private network delivered via Verizon Business' innovative global-provisioning Ethernet platform, is ideal for organizations seeking to link multiple sites in a flexible, operationally efficient model. VPLS is protocol-independent, supporting both IP and non-IP applications, which allows customers to retain complete control of their own routing. In addition, VPLS allows customers to access Verizon's extensive portfolio of Ethernet services and other data networking services offered by the company.
In a challenging economy, Verizon Business' global expansion of VPLS service and growth of its Ethernet portfolio is a good-news story," said Stan Hubbard, senior analyst with Heavy Reading. The company's global provisioning platform for enabling a seamless experience, long history delivering Ethernet services, broad portfolio and stability will certainly all appeal to multinational customers.
VPLS is an optimal platform for converged networking as it allows for prioritization of applications via multiple classes of services (CoS). An organization can customize prioritization to ensure that business-critical applications receive the highest priority across the network. Verizon Real-time CoS, for example, makes VPLS ideal for carrying latency-sensitive traffic such as voice-over-IP (VoIP) and digital video. VPLS also enables customers to provision their network bandwidth from 1 megabit per second to gigabit per second and beyond, enabling efficient and cost-effective transmission of voice and data traffic. And VPLS is backed by robust service level agreements (SLAs), which customers expect from a carrier-class wide area network service." END - There was no direct link in the Verizon Press Release for more information.

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Special: Up to $6,000 in discounts are available for 2010 scheduling before December 1.

BOULDER - November 3, 2009 - OCS Forum (http://www.ocsforum.com) announced its new OCSR2-2010 Ultimate course. "R2 and R3 coming in 2010 confirms Microsoft place in the new telecommunications networking business," noted Tom Cross OCS Forum CEO. "R2 is having a significant impact on corporate voice telecommunications strategies indicating the end of the TDM-time division multiplexed PBX-Private Branch eXchange systems is now insight. Microsoft is also driving companies like Cisco, Nortel, Avaya, NEC, Mitel, ShoreTel to rethink their featuresets and capabilities because while R2 is a new game when R3 is released in 2010, their days are numbered," Cross commented.
This five -day (5-day) "hands-on" lab course with 700+ page manual focuses on the core components of OCS 2007 R2, including:
• Instant Messaging (IM) between everyone in the organization in the office or remote
• Application and Desktop sharing for true collaboration
• Audio/Video Conferencing including internally hosted audio conference calls and Live Meetings
• Integration with Exchange Server 2007 Unified Messaging
• Securing the environment to protect communications
The course provides many hands-on labs to practice and reinforce learning of many new concepts. After completing this course, students should be able to design, install, configure, maintain, monitor, and troubleshoot the core components of OCS 2007 R2. A complete outline is available at:
http://www.ocsforum.com/news/Course%20Overview-2010k.htm

About OCS Forum

OCS Forum is a vendor-independent laboratory environment designed for learning, technical guides, knowledge resources and online "live" services. OCS Forum provides consulting, training, case studies, white papers, speaking engagements, market/customer research, network planning and other services. For more go to http://www.ocsforum.com.

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I used Carbonite for more than a year and when I needed to restore my files, because of, what they said, was lack of an encryption key, I was unable to restore my files. That is, it was my fault. In addition, I asked for a refund and got this "Carbonite offers free trials in order to allow customers to evaluate Carbonite's service prior to purchase. By purchasing a subscription, you acknowledge that you are aware of this opportunity to "try before you buy" and have either already taken advantage of it or decided not to do so. In light of the above we will not be able to offer any refunds for Carbonite subscription purchases except in cases of product defects that we are unable to correct."

My advice is be very careful of automatic backup systems because the small fee they charge may not ever be large enough if you loose a file.

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There will be many "flavors" of SIP trunks. Here are some examples:
1 - Public Internet - performance and security based on WAN connection - via hosted SIP trunks from a provider
2 - Private MPLS-Multi-Protocol Label Switching-VPN-Virtual Private Network used for customers with several sites and not visible for other customers via a private dedicated circuits
3 - Over IPSec VPNs for more security - requires key management, IPSec-IP Security implementation, real-time encryption & decryption, and potential multiple networks
4 - With TLS-Transport Layer Security and SRTP-Secure Real-time Transport Protocol used for highly secure situations. This is where Port Level Security or TLS-Transport Layer Security takes place. That is, control access by the Port Number such as deny or access to Port 5060-5061 for SIP or access to any other function. This is called a Stateful Inspection for a firewall to check, alert or audit the status (state) of the TCP connection - SYN, SYN-ACK or FIN.

In summary, depending on your own network strategy, security requirements and flexibility will drive whether you build or buy.

About OCS Forum

This tutorial is provided by TECHtionary.com and OCSForum.com sponsor of
OCS Forum 2010 Expo - June 15-16 - Boulder, Colorado. OCS Forum is a vendor-independent laboratory environment designed for learning, technical guides, knowledge resources and online "live" services. OCS Forum provides planning, project management, consulting, training, case studies, white papers, speaking engagements, market/customer research, network planning and other services. For more go to http://www.ocsforum.com. Call Tom Cross 303-594-1694 or cross@gocross.com for more information and scheduling.

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Meanwhile here are more details pertaining to this issue:
A CODEC-COder-DECoder (also known as an encoder-decoder and COmpression-DECompression system when used in video systems) is a computer chip (semiconductor) digital signal processing system. Source codecs are designed specifically for speech, whereas Waveform codecs work well with any type of sound. Depending on the audio or voice application would drive the selection of the Source or Waveform CODEC. While there are many types of CODECs, G.711 & G.729 are the two most-commonly CODECs used in VoIP systems. Shown in the animated tutorial is a G.711 encoded audio stream is 64/56/48 KBPS-Kilo Bits Per Second. Each 13/14 bit sample of the original signal (voice-audio) is encoded into an eight Byte/Octet. Compression algorithms operate by sampling voice and quantizing the analog sound into digital values. G.711 is based on traditional Nyquist-Shannon sampling theorem that the sampling frequency rate must be at least twice as high as the highest input frequency for the result to closely resemble the original signal. A 4,000 Hz-Hertz voice pattern would be sampled at a rate of 8,000 BPS-Bits Per Second. Next, in the animated tutorial here is a G.729 coding at 8,000, not 64,000 samples per second. Transcoding is also related to the concept of Tandem Encoding or Tandem Compression. Tandem Encoding is traditional the concept of the transfer of TDM traffic between different telephone carriers via tandem Class 4/5 switches as they process telephone calls. Tandem Encoding is also the process of interconnecting same or different company packet voice. That is, different CODECs (e.g. G.711/729) may be used at different locations within the same company and more likely between different companies. Most SIP providers support G.711 and G.729. RTA-Real-Time Audio developed by Microsoft is used with OCS-Office Communications Server. MOS-Mean Opinion Scores reduces rapidly with each time a voice conversation is processed by a CODEC. Whether you call it Transcoding or Tandem Encoding, the CODEC in a SIP network should be standardized whenever possible.

Here's the "so what" or "why should I care about this." For example, different CODEC sampling rates may start synchronized but shortly become un-synchronized which can cause encoding problems and voice to jitter. To measure and manage jitter, RTP-Real Time Protocol uses the time-stamp function in the protocol to assess jitter based on the delay between arrival (interarrival) times of each packet. Changing the number of bits sampled and quantized can dramatically impact the voice quality. However, LAN-Local Area Network and WAN-Wide Area Network bandwidth limitations may have an equal or greater impact on VoIP performance. Echo can also occur as a result of Asynchronous Transcoding. Transcoding is the process of conversion between circuit-switched (PSTN-Public Switched Telephone Network) and packet-switched networks such as Frame Relay, IP-Internet Protocol and ATM-Asynchronous Transfer Mode. The point is that Asynchronous Transcoding should be avoided. According to Intel, "The term "asynchronous transcoding" refers to a situation when, for example, one endpoint is talking G.711 to another endpoint talking G.729 or two different encodings." According to Cisco, "Although it can seem logical from a financial standpoint to convert all calls to low-bit rate codecs to save on infrastructure costs, exercise additional care when you design voice networks with low-bit rate compression. There are drawbacks to compressing voice. One of the main drawbacks is signal distortion due to multiple encodings (called tandem encodings). For example, when a G.729 voice signal is tandem encoded three times, the MOS-Mean Opinion Score drops from 3.92 (very good) to 2.68 (unacceptable). Another drawback is codec-induced delay with low bit-rate codecs." Our analysis and recommendation is to always use G.711 based on the assumption that processing voice across other networks will probably use lower-bit rate CODECs reducing MOS quality. In other words, start with quality and hopefully but not likely you will end with quality. In addition, there is no requirement by any customer or vendor to provide end-to-end G.711 or any other CODEC. If you consider multi-party conference calls, the problem gets compounded.

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