25-August-2008 • 10:37 pm
H.323 is a standard for communication protocols from the International Telecommunications Union Telecommunication Standardization Sector (ITU-T); Version 4 is the current version. H.323 was created to provide multimedia communication across a packet network. The protocol can handle video and data, in addition to audio.
Gateways that use H.323 do not depend on a call agent, as with Media Gateway Control Protocol (MGCP). H.323 is the default gateway protocol on Cisco routers.
Because gateways function as H.323 endpoints, they provide admission control, address lookup and translation, and accounting services.
In an environment in which both gatekeepers and gateways are used, only gateways are configured to send VoIP.
H.323 Specifications
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H.225: Handles call setup and teardown between H.323 devices on a packet-based network, terminal to gatekeeper signaling using Registration, Admission, and Status Protocol (RAS), and call signaling. H.323 can use ISDN Q.931 signals, formatted as H.225 messages, to interoperate with legacy voice networks.
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H.235: Specifies security for messages between the gateway and gatekeeper.
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H.245: Controls the traffic flow, performs DTMF Relay, limits media transmission rates, negotiates capability, and controls opening and closing channels for media streams. Uses TCP.
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H.261/ H.263: Specify video conferencing standards.
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H.450: Controls supplementary services between H.323 entities. Examples of supplementary services include call waiting, hold, transfer, park, and pickup.
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T.120: Used for real-time multipoint data transfer during videoconferences. Allows application sharing, whiteboarding, and file transfer. Uses TCP.
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H.320: Defines the standard for video conferencing over ISDN networks. H.320 uses H.221 frames for media. It requires a gateway to interwork with H.323 conferencing over IP because H.221 frames must be translated into RTP packets, and vice versa.
Filed under: » CCVP, » Gateway, » H.323, » Review Notes, » Voice
H.323
- The H.323 protocol was designed by the ITU-T and initially approved in February 1996. It was developed as a protocol that provides IP networks with traditional telephony functionality.
- In Cisco IP Communications environments, H.323 is widely used with gateways, gatekeepers, and third-party H.323 clients, especially video terminals. You configure connections between devices using static destination IP addresses.
- Because H.323 is a peer-to-peer protocol, H.323 gateways are never controlled by Cisco Unified CallManager. Therefore, H.323 gateways are never registered at the Cisco Unified CallManager. Only the IP address is seen by the Cisco Unified CallManager to confirm that communications is possible.
MGCP
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MGCP is a plain-text protocol used by call-control devices to manage IP telephony gateways. MGCP was defined under RFC 2705, which was updated by RFC 3660, and superseded by RFC 3435, which was updated by RFC 3661.
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is a client/server protocol that allows a call agent (such as Cisco Unified CallManager) to take control of a specific voice port on a gateway.
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With this protocol, the Cisco Unified CallManager knows of and controls individual voice ports on the gateway. It allows complete control of the dial plan from Cisco Unified CallManager, and gives CallManager per-port control of connections to the PSTN, legacy PBX, voice mail systems, POTS phones, and so forth.
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This is implemented with use of a series of plain-text commands sent over User Datagram Protocol (UDP) port 2427 between the Cisco Unified CallManager and the gateway.
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It is important to note that for an MGCP interaction to take place with Cisco Unified CallManager, the gateway must have Cisco Unified CallManager support.
- A PRI and BRI backhaul is an internal interface between the call agent (such as Cisco Unified CallManager) and Cisco gateways. It is a separate channel for backhauling signaling information. A PRI backhaul forwards PRI Layer 3 (Q.931) signaling information via a TCP connection.
SIP
- SIP is a protocol developed by the Internet Engineering Task Force (IETF) Multiparty Multimedia Session Control (MMUSIC) Working Group as an alternative to H.323.
- SIP features are compliant with IETF RFC 2543, published in March 1999, RFC 3261, published in June 2002, and RFC 3665, published in December 2003.
- Because it is a common standard based on the logic of the World Wide Web and very simple to implement; SIP is widely used with gateways and proxy servers within service provider networks for internal and end-customer signaling.
- SIP is a peer-to-peer protocol where user agents (UAs) initiate sessions, like H.323. But unlike H.323, SIP uses ASCII-text-based messages to communicate. Therefore, you can implement and troubleshoot it very easily, and analyze the incoming signaling traffic content very simply.
- Because SIP is a peer-to-peer protocol, the Cisco Unified CallManager does not control SIP devices, and SIP devices do not register with Cisco Unified CallManager. As with H.323 gateways, only the IP address is available on Cisco Unified CallManager to confirm that the communications between the Cisco Unified CallManager and the SIP voice gateway is possible.
SCCP (Skinny Call Control Protocol)
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SCCP is a Cisco proprietary protocol that is used for the communications between Cisco Unified CallManager and terminal endpoints (based on Selsius prorocol, that was bought by Cisco).
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SCCP is a stimulus protocol, meaning any event (such as on-hook, off-hook, buttons pressed, and so on) causes a message to be sent to the Cisco Unified CallManager.
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The Cisco Unified CallManager then sends specific instructions back to the device to tell it what to do about the event.
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Therefore, each press on a phone button causes data traffic between the Cisco Unified CallManager and the terminal endpoint. SCCP is widely used with Cisco IP phones.
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The major advantage of SCCP within Cisco Unified CallManager networks is its proprietary nature, which allows you to make quick changes to the protocol and add features and functionality.
Signaling Protocols Comparison (H.323, MGCP, SIP, SCCP):
H.323
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The H.323 protocol suite is a peer-to-peer protocol. The necessary gateway configuration is relatively complex, because you need to define the dial plan and route patterns directly on the gateway.
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Examples of H.323-capable devices are the Cisco VG224 Analog Phone Gateway and the Cisco 2600XM Series, Cisco 2800 Series, 3700 Series, and 3800 Series routers.
- The H.323 protocol is responsible for the entire signaling between the Cisco Unified CallManager cluster and the gateway. The ISDN protocols, Q.921 and Q.931, are only used on the ISDN link to the PSTN.
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NOTES:
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Q.921 – Also referred to as LAPD (Link Access Protocol – D Channel) and a close cousin of HDLC, is the Data Link protocol used over ISDN’s D channel. [ Reference:
http://www.freesoft.org/CIE/Topics/125.htm ]
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Q.931 - is ISDN’s connection control protocol, roughly comparable to TCP in the Internet protocol stack. Q.931 doesn’t provide flow control or perform retransmission, since the underlying layers are assumed to be reliable and the circuit-oriented nature of ISDN allocates bandwidth in fixed increments of 64 kbps. Q.931 does manage connection setup and breakdown. Like TCP, Q.931 documents both the protocol itself and a protocol state machine. [ Reference:
http://www.freesoft.org/CIE/Topics/126.htm ]
MGCP
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The MGCP protocol is based on a client/server architecture.
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That simplifies the configuration because the dial plan and route patterns are defined directly on the Cisco Unified CallManager within the cluster.
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Examples of MGCP-capable devices are the Cisco VG224 Analog Phone Gateway and the Cisco 2600XM Series, 2800 Series, 3700 Series, and 3800 Series routers. Non-IOS MGCP gateways include the Cisco Catalyst 6608-E1 and Catalyst 6608-T1.
- MGCP is used to manage the gateway. All ISDN Layer 3 information is backhauled to the Cisco Unified CallManager. Only the ISDN Layer 2 information (Q.921) is terminated on the gateway.
SIP
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SIP is a peer-to-peer protocol.
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The configuration that is necessary for the gateway is relatively complex because the dial plan and route patterns need to be defined directly on the gateway.
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Examples of SIP-capable devices are the Cisco 2800 Series and 3800 Series routers.
- The SIP protocol is responsible for the entire signaling between the Cisco Unified CallManager cluster and the gateway. The ISDN protocols, Q.921 and Q.931, are only used on the ISDN link to the PSTN.
SCCP
- SCCP works in a client/server architecture in the same way as MGCP does. Therefore, it simplifies the configuration of SCCP devices such as Cisco IP phones and Cisco ATA 180 Series and VG200 Series FXS gateways.
- SCCP is used on Cisco VG224 and VG248 analog phone gateways.
- ATA’s enable communications between Cisco Unified CallManager and the gateway.
- The gateway then uses standard analog signaling to the analog device connected to the FXS port. Recent versions of Cisco IOS voice gateways, for example, the 2800 series, also support SCCP controlled FXS ports.
IP-to-IP Gateways
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Cisco Multiservice IP-to-IP Gateways (IPIPGWs) are the next-generation gateways within unified IP communications networks.
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They facilitate connectivity between independent VoIP networks by enabling VoIP and videoconferencing calls from one IP network to another.
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The Cisco Multiservice IPIPGW performs most of the functions of a PSTN-to-IP gateway, but typically joins two IP call legs, rather than a PSTN and an IP call leg.
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Media packets (RTP packets) can flow either through the gateway (thus hiding the networks from each other) or around the gateway, if configured to do so.
- Because the Cisco Multiservice IPIPGW is usually used to interconnect two independent networks like service provider networks or an enterprise network to a VoIP service provider, the gateways are generally configured to terminate the RTP. That makes it possible to have a single point of contact between those two networks, which leads to more security between those networks because the IP-to-IP gateway then functions as a proxy for signaling and voice traffic.
- The Cisco Multiservice IPIPGW also allows the use of two different protocols on both sides. That makes interconnections between two different networks easier and allows simple upgrades from PSTN links to IP links because it doesn’t matter which protocols are already used within the existing network.
Download: [ PDF copy here ]
References:
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- Cisco PEC (requires a valid account)
Filed under: » CCVP, » Gateway, » Review Notes, » Voice
A voice gateway allows terminals of one type, such as H.323, to communicate with terminals of another type, such as a PBX, by converting protocols.Gateways connect a company network to the PSTN, a PBX, or individual analog devices such as a phone or fax.
Types of Cisco access gateways:
- Analog Gateways:
- Analog Station – gateways that connect an IP telephony network to plain old telephone service (POTS). They provide Foreign Exchange Station (FXS) ports to connect analog telephones, interactive voice response (IVR) systems, fax machines, PBX systems, and voice-mail systems.
- Analog Trunk – gateways that connect an IP telephony network to the PSTN central office (CO) or a PBX. They provide Foreign Exchange Office (FXO) ports for PSTN or PBX access and recEive and transMit (E&M) ports for analog trunk connection to a legacy PBX. To minimize any answer and disconnect supervision issues, use digital gateways whenever possible. Analog direct inward dialing (DID) is also available for PSTN connectivity.
- Digital Gateways: Cisco access digital trunk gateways connect an IP telephony network to the PSTN or to a PBX via digital trunks, such as PRI common channel signaling (CCS), BRI, and T1 or E1 channel associated signaling (CAS). Digital T1 PRI trunks may also connect to certain legacy voice-mail systems.
IP telephony gateways should meet these core feature requirements:
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Gateway protocol support: Gateways support H.323, Media Gateway Control Protocol (MGCP), session initiation protocol (SIP), and Skinny Client Control Protocol (SCCP). H.323 and SIP gateways do not need a call control agent. MGCP and SCCP are streamlined protocols that only work on a network in which a call agent such as a Cisco Unified CallManager is present.
“He who wrestles with us strengthens our nerves and sharpens our skill. Our antagonist is our helper” – Edmund Burke, 1729-1797
Download: [ PDF copy here ]
Reference: Cisco PEC (requires a valid account)
Filed under: » CCVP, » Gatekeeper, » Gateway, » Review Notes, » Voice
Recieved a mail from Cisco:
Cisco is now soliciting beta candidates for Cisco’s upcoming CCIE Wireless Written Exam. We are looking for an exclusive set of professional and expert level Wireless Networking Engineers who can dedicate 3 hours of their time to take the beta exam.
The CCIE Wireless certification, to be launched later this year, will validate that professionals have the expertise to design, manage and support mission and business critical wireless networks and the job skills and technical knowledge required of expert level network IT practitioners. This written exam is the first step in obtaining the CCIE Wireless certification. Successful candidates will have mastered broad theoretical knowledge of wireless networking and demonstrated a readiness for the CCIE Wireless lab examination. Be one of the first wireless professionals to get a peek at the new CCIE Wireless exam.
- Location: Pearson Vue Testing Centers, Worldwide
- Registration Date: October 7
- Last Test Date: November 14, 2008
- Cost: $US50
- Exam Number/Name: 351-050 CCIE Wireless Beta Written Exam
To learn more about the exam blueprint, job skills and reference material, please go to http://www.cisco.com/web/learning/le3/ccie/wireless/index.html
“There came a time when the risk to remain tight in the bud was more painful than the risk it took to blossom” – Anais Nin, 1903-1977
Filed under: » CCIE, » Exam
» Optimize Phase Overview
- Ensure customer’s network is operating at peak performance.
- Ensure customer’s network is resolving problems quickly.
- Ensure customer’s network is adapting the architecture, operation, and performance to chnaging business goals.
» Business Case Alignment
- Assess the ROI
- Assess other business benefits of the solution.
» Technology Assessment
- Assess the routing and switching system.
- Drive continuous improvements by recommending remediation measures including:
- Device configuration optimization.
- Capacity planning.
- Traffic analysis.
- Security assessment.
- Quality issue resolution.
- Technology Assessment Activity:
- System performance analysis
- Measure the solution performance, availability, capacity, security, and software functionality
- Security review of infrastructure
- Develop and deliver technology assessment report
» Operations Assessment
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Assess the current state of customer operations and network management.
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Identify issues and opportunities for improving the management of their routing and switching system.
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Operation Assessment Activities:
» Security Assessment
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Obtain, review, determine, and document security procedures.
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Upgrade requirements.
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Evaluate the efficiencies of the security infrastructure.
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Security Assessment Activities:
» Recommended Skills
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Typical job roles include AM’s, SE’s, FE’s, and network consulting engineers (NCE’s).
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The recommended skills needed to fulfill the defined activities are:
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Demonstrate an understanding of the existing routing and switching network.
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The ability to assess the customer’s evolving business requirements and identify trends in operational processes.
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An understanding of account management, market conditions, sales methodologies, industry routing and switching operations, and security leading practices.
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The capability to recognize opportunities to position and sell additional routing and switching technologies.
REFERENCE: Cisco PEC (Requires valid user login)
“The only difference between stumbling blocks and stepping stones is how we use them.” – Author unknown
Filed under: » CQS-ARSFE, » Lifecycle, » Review Notes
» Operate Phase Overview
- Ensure the solution is operating efficiently.
- Ensure the solution is highly available.
» Operations Setup
- System administration and backup.
- Assessment management.
- Scheduled maintenance.
» Systems Monitoring
- Monitor, manage, and report on service level metrics and abnormal events or trends that may effect the enterprise routing and switching system.
» Incident Management
- Classifying and prioritizing the incident.
- Isolating and resolving the incident.
- Scheduled maintenance.
- Recovering from the incident outage.
- Validating the resolution.
- Tracking and monitoring progress.
- Closing the incident.
» Problem Management
- Identify, as well as resolve, recurring incidents.
- Analyze incident trends.
- Activities:
- Identify problem
- Manage problem
» Change Management
- Originate and evaluate changes.
- Accept and schedule changes.
- Execute changes.
- Communicate changes.
- Conduct post-change evaluation.
- Accept and close changes.
» Configuration Management
- Check that changes in the system infrastructure have been recorded correctly.
- Monitor the status of components.
- Activities:
- System configuration management database
- Verify configuration management database
» Supplier Management
- Check that changes in the infrastructure have been recorded correctly.
- Manage requisitions with suppliers.
- Manage settlements and billing activities.
- Manage contracts between the enterprise and suppliers.
» Security Management
- Define processes and principles to address security-related issues.
- Provide ongoing management to protect confidentiality, integrity, and availability of information.
- Security Management Activities:
- Security incident management
- Identify management
- Security configuration management
- Security content delivery management
- Security policy administration
» Service Review
- Assist customer in identifying best practices to monitor system performance and respond to trouble reports.
» Recommended Skills
- Typical job roles include AM’s, SE’s, and FE’s.
- The recommended skills needed to fulfill the defined activities are:
- Demonstrate an understanding of the proposed routing and switching solution.
- The ability to support a routing and switching solution and troubleshoot network problems.
- The capability to provide configuration, change management, incident, and problem management activities.
REFERENCE: Cisco PEC (Requires valid user login)
Filed under: » CQS-ARSFE, » Lifecycle, » Review Notes
» Implement Phase Overview
- The new technology solution is installed with minimal disruption to the existing network.
- Vulnerabilities are assessed and minimized.
» Project Planning
- Develop project management, escalation, and communication plans.
- Conduct an internal kickoff meeting.
» Project Kickoff
- Conduct the project kickoff meeting.
» Staging Core Network Services: Routed and Switched Environments
- Provide a plan detailing the installation requirement tasks.
- Stage tasks in a controlled implementation environment.
- Activities:
- Install system components per staging plan
- Staging plan (configure and document solution)
- Execute test cases per the staging plan
» Phased Implementation
- Configure and integrate enterprise routing and switching system components for pilot sites.
- Activities:
- Site preparation for system implementation
- Install, configure, integrate, and test infrastructure
- Document implemented components, devices, and applications
- Host hand-off and support introduction meeting
» Full System Migration
- Migrate all sites, end-users and network services.
» Acceptance Testing
- Verify that the system meets the customer’s solution requirements
- Verify that the system is ready for production.
- Activities:
- Prepare for acceptance test plan execution
- Execute systems acceptance test plan
- Present and review test results
» Staff Training
- Develop the class scheduling, enrollment, communication plan, course outlines, training schedule and locations, coordination of training vendors, and training budgets.
» Post Implementation Support Hand-off Meeting (Operations Implementation)
- Coordinate a meeting to provide details on and discuss the ongoing support and services to be provided.
- Activities:
- Review customer operations plan
- Prepare for hand-off meeting
- Host a hand-off meeting
- Execute customer operations plan
- SMARTnet only hand-off meeting
- Operations services hand-off meeting
- Partner value added support hand-off meeting
- Verify customer understanding
» Project Closeout
- Recap the solution implementation to gather customer feedback, gauge profitability, identify lessons learned, and incorporate into leading practices.
» Recommended Skills
- Typical job roles include SE’s, FE’s, and PM’s.
- The recommended skills needed to fulfill the defined activities are:
- Demonstrate an understanding of the proposed routing and switching solution.
- The ability to provide staff training.
- Excellent documentation and writing skills.
- Demonstrate understanding of technical support options.
- Technical deployment and project management skills.
REFERENCE: Cisco PEC (Requires valid user login)
Filed under: » CQS-ARSFE, » Lifecycle, » Review Notes
» Design Phase Overview
- Design solution is developed to meet business requirements, and foresee and prevent potential network bottlenecks
» Design Project Kickoff
- Host a design workshop to:
- Confirm dates, roles, and responsibilities.
- Confirm that all planning information is complete.
- Discuss and document the progress for the remediation plan.
» Detailed Design Development: Design Workshop
- Provide a comprehensive detailed design for the customer routing and switching system.
- Detailed Design Development: Design Workshop Activity:
- Design routing and switching infrastructure
- Design recommendations for a switched environment
- Design recommendations for a routed environment
- Design MPLS WAN
- DMVPN design development (Here is a tutorial of DMVPN by Petr Lapukhov of Internetwork Expert)
- Design routing and switching security architecture
- Present low-level design to customer
» Detailed Design Validation
- Validate the design of the:
- Routing and switching WAN infrastructure.
- Routing environment.
- Security architecture design.
- Interfaces to third-party systems.
- Present the low-level design validation to the customer.
- Detailed Design Validation Activities:
- Validate design core network services WAN infrastructure
- Validate design routing environment (internal/ external)
- Validate security architecture design
- Validate design interfaces to 3rd-party systems and databases
- Present low-level design validation to customer
» Detailed Design Customer Sign-off
- Review the low-level design with the customer.
- Obtain a signed Letter of Understanding.
» Implementation Plan Development
- Provide a site-specific implementation plan that defines:
- Activities.
- Configurations.
- Commissioning test plans.
- Implementation Plan Development Activities:
- Site-specific implementation requirements
- Create a site-specific network implementation plan
- Gather and verify full system migration requirements
- Develop full system migration strategy
- Define migration team roles and responsibilities
- Develop implementation schedule
- Present final network implementation plan
» Operations Plan Development
- Operational processes for the routing and switching system.
- A plan to implement the new processes.
- A process readiness test plan.
- Operations Plan Development Activities:
- Review existing process and flows
- Develop methods and procedures
- Develop plan to implement operations
- Develop test plan for operational processes
- Present operations plan
» Staging Plan Development
- Provide a plan detailing the installation requirement tasks.
- Stage the tasks in a controlled implementation environment.
- Staging Plan Development Activities:
- Collect and verify staging requirements
- Staging plan development
- Present staging plan
» Systems Acceptance Test Plan Development
- Verify that the deployed system meets the customer’s needs.
- Verify tat the system is ready for the production environment.
- Systems Acceptance Test Plan Development Activities:
- Collect and verify solution accepted requirements
- Acceptance test plan development
- Present acceptance test plan
» Staff Plan Development
- Assess the skills and knowledge required to support the customer’s proposed system.
- Analyze and define the training and development requirements for each support role.
» Recommended Skills
- Typical job roles include AM’s, SE’s, FE’s and PM’s.
- The recommended skills needed to fulfill the defined activities are:
- The ability to manage complex projects and demonstrate an understanding of the solution.
- The ability to design a solution that meets the customer requirements.
- The ability to validate the routing and switching design.
- An understanding of the routing and switching implementation and operational requirements.
REFERENCE: Cisco PEC (Requires valid user login)
Filed under: » CQS-ARSFE, » Lifecycle, » Review Notes
