13683 Courses in Cardiff delivered Online

IP broadcast training course description A current hot topic in recent years has been the provision of multimedia services over IP networks aka triple or quadruple play. This course investigates the characteristics of video transmission and then studies the impact on IP networks. What will you learn Use Wireshark to analyse and troubleshoot TV streams. Describe techniques, which can be used in IP to provide low uniform delay. Evaluate IPTV technologies. Design data networks, which will support IPTV. IP broadcast training course details Who will benefit: Anyone working in broadcast. Prerequisites: TCP/IP foundation for engineers Duration 3 days IP broadcast training course contents What is IPTV? What is IP? What is TV? Pixels, frames, colour, digital modulation, digital video broadcasting. SDTV, HDTV, 4K. IPTV architectures, Contribution, distribution, delivery. IPTV standards. Hands on Base IP connectivity, VLC. IPTV protocol stacks IP, TCP, UDP, RTP. IPv6. HTTP. Bandwidth requirements. Hands on IPTV bandwidth calculations. Video codecs What is a CODEC, pictures and audio, digitisation, sampling, quantisation, encoding, compressing. MPEG, bit rates, resolution. I, B, P frames, GOP. MPEG 2, MPEG 4, H.264, H.265, VP9, AV1. Hands on Analysing MPEG frames. IP issues Quality vs. bandwidth. Bandwidth, delay, latency, jitter, signalling. Routers. Hands on Analysing jitter and other performance issues. IPTV performance and QoS IP DSCP field, queuing strategies; FIFO, WFQ, custom, priority, RED. Differentiated services, Diffserv. 802.1Q. Traffic shaping. QoE. Hands on best effort versus prioritisation. UDP versus TCP Reliable, unreliable, connection oriented, connectionless. Broadcasts, multicasts and unicasts. TCP flow control, TCP and performance. Hands on TCP window sizes. RTP RTP, ports, mixers, translators, RTCP, SMPTE, FEC. Hands on RTP analysis with Wireshark. Multicasting Multicasting compared to unicasting and broadcasting, when to use and when not to use multicasting. IGMP, PIM-SM, SSM. MLD. Hands on Analysing multicast streams. OTT TV HTTP, HTTPS, Chunked HTTP. Adaptive streaming. HTML5. DASH vs HLS. Hands on Analysing HTTP streams. Security Firewalls, TLS, DRM, watermarking. Encryption. Geolocation. VPNs. IPTV architecture and other protocols Content providers, Service providers, delivery networks, home networks. Caching, Service discovery. RTSP. SAP, SDP. DHCP, DNS, NTP

IPTV training course description A current hot topic in recent years has been the provision of multimedia services over IP networks aka triple or quadruple play. This course investigates the characteristics of video transmission and then studies the impact on IP networks. What will you learn Use Wireshark to analyse and troubleshoot TV streams. Describe techniques, which can be used in IP to provide low uniform delay. Evaluate IPTV technologies. Design data networks, which will support IPTV. IPTV training course details Who will benefit: Anyone working with IPTV. Prerequisites: TCP/IP Foundation for engineers Intro to data communications & networking. Duration 3 days IPTV training course contents What is IPTV? What is IP? What is TV? Pixels, frames, colour, digital modulation, digital video broadcasting. SDTV, HDTV, 4K. IPTV architectures, Contribution, distribution, delivery. IPTV standards. Hands on Base IP connectivity, VLC. IPTV protocol stacks IP, TCP, UDP, RTP. IPv6. HTTP. Bandwidth requirements. Hands on IPTV bandwidth calculations. Video codecs What is a CODEC, pictures and audio, digitisation, sampling, quantisation, encoding, compressing. MPEG, bit rates, resolution. I, B, P frames, GOP. MPEG 2, MPEG 4, H.264, H.265, VP9, AV1. Hands on Analysing MPEG frames. IP issues Quality vs. bandwidth. Bandwidth, delay, latency, jitter, signalling. Routers. Hands on Analysing jitter and other performance issues. IPTV performance and QoS IP DSCP field, queuing strategies; FIFO, WFQ, custom, priority, RED. Differentiated services, Diffserv. 802.1Q. Traffic shaping. QoE. Hands on best effort versus prioritisation. UDP versus TCP Reliable, unreliable, connection oriented, connectionless. Broadcasts, multicasts and unicasts. TCP flow control, TCP and performance. Hands on TCP window sizes. RTP RTP, ports, mixers, translators, RTCP, SMPTE, FEC. Hands on RTP analysis with Wireshark. Multicasting Multicasting compared to unicasting and broadcasting, when to use and when not to use multicasting. IGMP, PIM-SM, SSM. MLD. Hands on Analysing multicast streams. OTT TV HTTP, HTTPS, Chunked HTTP. Adaptive streaming. HTML5. DASH vs HLS. Hands on Analysing HTTP streams. Security Firewalls, TLS, DRM, watermarking. Encryption. Geolocation. VPNs. IPTV architecture and other protocols Content providers, Service providers, delivery networks, home networks. Caching, Service discovery. RTSP. SAP, SDP. DHCP, DNS, NTP Hands on Fixing the network.

LTE training course description This course is designed to give the delegate an understanding of the technologies used within a 3G UMTS mobile network. During the course we will investigate the UMTS air interface and the use of Wideband-Code Division Multiple Access (WCDMA) to facilitate high speed data access, together with HSPA to offer mobile broadband services. We will describe the use of soft handover rather than hard handover procedures and soft capacity sharing. The course includes a brief exploration of the UMTS protocol stack and the use of PDP Context and QoS support features. What will you learn Explain the 3G UMTS architecture. Describe the role of a Drifting & Serving RNC. Explain the use of ARQ & HARQ for mobile broadband. Describe how IMS integrates into the architecture. Describe the use of Media Gateway Controllers. Identify the temporary identities used within 3G UMTS. LTE training course details Who will benefit: Anyone working within the telecommunications area, especially within the mobile environment. Prerequisites: Mobile communications demystified Telecommunications Introduction Duration 2 days LTE training course contents LTE Introduction The path to LTE, 3GPP. LTE to LTE advanced. LTE Architecture The core, Access, roaming. Protocols: User plane, Control plane. Example information flows. Bearer management. Spectrum allocation. LTE technologies Transmission, reception, OFDMA, multiple antenna, MIMO. LTE Air interface Air interface protocol stack. Channels, Resource Grid, cell acquisition. Up and downlink controls. Layer 2 protocols. Cell acquisition Power on, selecting networks and cells. RRC connection. Attach procedure. Mobility management Roaming, RRC_IDLE, RRC_CONNECTED, cell reselection, handover, interoperation with UMTS and GSM networks. Voice and text IMS, QoS, policy and charging.

Introducing our Local Relationship Counselling Services Package – a comprehensive solution designed to strengthen and nurture your relationship. At Miss Date Doctor, we understand that every couple’s needs are unique, which is why we offer a range of tailored services to cater to your specific requirements. With the flexibility to choose any of our offices, we ensure convenience and accessibility for all our valued customers. Our team of expert relationship coaches is dedicated to helping you navigate through the challenges and complexities of modern relationships. Our Local Relationship Counselling Services Package covers a wide array of areas, addressing common concerns and providing guidance in the following key areas: Communication Enhancement: Effective communication is the cornerstone of any successful relationship. Our coaching package equips you with valuable tools and techniques to improve communication, fostering greater understanding and connection between you and your partner. Conflict Resolution: Conflicts are inevitable in relationships, but how we handle them can make all the difference. Our relationship coaching services provide you with valuable insights and strategies to resolve conflicts amicably, promoting harmony and mutual growth. Trust Building: Trust forms the foundation of a healthy relationship. Our experienced coaches will guide you through exercises and discussions aimed at rebuilding trust, overcoming past issues, and cultivating a stronger bond. Intimacy and Emotional Connection: Enhancing intimacy and fostering emotional connection are vital for a fulfilling relationship. Our package offers guidance on building intimacy, reconnecting on a deeper level, and reigniting the spark that initially brought you together. Goal Setting and Future Planning: Together, we’ll help you and your partner identify shared goals, clarify individual aspirations, and work towards building a shared vision for the future. Our relationship coaching services provide a roadmap for aligning your ambitions and creating a fulfilling life together. By choosing our Local Relationship Counselling Services Package, you’re investing in a supportive and confidential environment where you and your partner can explore your relationship dynamics and work towards a happier, healthier future. Our commitment to personalized care, coupled with the freedom to select the most convenient office location for your sessions, ensures that you receive the best possible support for your unique relationship journey. Don’t let the challenges of maintaining a fulfilling relationship overwhelm you. Take the first step towards a more harmonious partnership by opting for our Local Relationship Counselling Services Package today. Trust in our expertise, and let us guide you towards a happier, more fulfilling relationship. 1 hour 3 sessions https://relationshipsmdd.com/product/local-relationship-counselling-services-package/

Python training course description This Python course focusses on teaching Python for use in network automation and network DevOps. We focus on getting delegates up and running with Python and network automation as quickly as possible rather than making them great programmers. In other words we concentrate on enabling delegates to use network automation libraries such as netmiko, NAPALM and Nornir, and APIs such as NETCONF and RESTCONF rather than enabling delegates to produce object oriented programs. Hands on sessions use Cisco and Juniper devices. What will you learn Run Python programs. Read Python programs. Write Python programs. Debug Python programs. Automate network tasks with Python programs. Configure network devices with Python. Collect data from network devices with Python. Python training course details Who will benefit: Network engineers. Prerequisites: TCP/IP Foundation Duration 5 days Python training course contents What is Python? Programming languages, Why Python? Python in interactive mode, Python scripts, ipython, Python version 2 versus version 3. A simple Python script. Comments. Hands on Installing Python, Hello world. A network example On box vs off box Python. telnet, ssh, NETCONF, HTTP, APIs, manufacturers and API support, analysis of a simple telnetlib program. Hands on Using Python to retrieve the configuration from a network device. Using wireshark to analyse the actions. Python basics I/O, operators, variables and assignment, types, indentation, loops and conditionals. Hands on Modifying the telnet program, changing configurations on a network devices. Functions, classes and methods What are functions, calling functions, builtin functions, useful builtin functions, file handling, classes, objects, creating instances. Hands on Storing configurations in files, configuring devices from files, using an inventory file to work on multiple devices. Libraries and modules Modules, files and packages, import, from-import, Python standard library, other packages, pip install, executing other programs. Managing python libraries. Hands on Using pip, installing and using ipaddress, subprocess to access netsnmp. For the more advanced, using the sockets library. Paramiko and netmiko SSH, enabling SSH on devices, keys. Paramiko versus netmiko, example scripts. pexpect. Hands on Configuring VLANs from Python. pySNMP Gathering facts using previous methods, SNMP review, pySNMP GET, pySNMP and SNMPv3. easySNMP library. Hands on Walking a MIB from Python. NETCONF What is NETCONF? Enabling NETCONF on devices, A first ncclient script, device handlers, get_config, edit_config, copy_config, delete_config, commit, validate, pyEZ, utils_config, utils.sw. Hands on Configuration using ncclient and PyEZ. This session is expanded for those interesting in JunOS automation. Manipulating configuration files Builtin functions, string handling. Unicode. Sequences, strings, lists, tuples. Dictionaries. TextFSM. Regular expressions. JSON, YAML, XML, YANG, Jinja2, templates. Hands on Jinja2 templating with Python to configure network devices. NAPALM Getters, configuration operations, supported devices, NAPALM transport, Config-replace, Config-merge, Compare config, Atomic changes, rollback. Example NAPLAM scripts. Hands on Using NAPALM to gather facts, Using NAPALM for configuration management REST and RESTCONF What is REST, HTTP methods, GET, POST, cURL, Postman, Python requests library. RESTCONF, a RESTCONF example. Hands on Modifying a configuration using RESTCONF. Scapy What is scapy, Scapy in interactive mode, Scapy as a module. Hands on Packet crafting from Python. Warning Errors and exceptions, Exception handling, try, except. Memory management. Garbage collection. Context management, With. Hands on Improving Python code. Nornir What is Nornir? A network automation framework, inventories, connection management and parallelization. Nornir architecture and other libraires. Hands on Setting up nornir, nornir fact gathering, nornir tasks. Optional Writing your own functions, Writing your own classes. pyntc. Hands on Writing reusable code.

Securing Linux systems training course description This course teaches you everything you need to know to build a safe Linux environment. The first section handles cryptography and authentication with certificates, openssl, mod_ssl, DNSSEC and filesystem encryption. Then Host security and hardening is covered with intrusion detection, and also user management and authentication. Filesystem Access control is then covered. Finally network security is covered with network hardening, packet filtering and VPNs. What will you learn Secure Linux accounts. Secure Linux file systems. Secure Linux access through the network. Securing Linux systems training course details Who will benefit: Linux technical staff needing to secure their systems. Prerequisites: Linux system administration (LPIC-1) Duration 5 days Securing Linux systems training course contents Cryptography Certificates and Public Key Infrastructures X.509 certificates, lifecycle, fields and certificate extensions. Trust chains and PKI. openssl. Public and private keys. Certification authority. Manage server and client certificates. Revoke certificates and CAs. Encryption, signing and authentication SSL, TLS, protocol versions. Transport layer security threats, e.g. MITM. Apache HTTPD with mod_ssl for HTTPS service, including SNI and HSTS. HTTPD with mod_ssl to authenticate users using certificates. HTTPD with mod_ssl to provide OCSP stapling. Use OpenSSL for SSL/TLS client and server tests. Encrypted File Systems Block device and file system encryption. dm-crypt with LUKS to encrypt block devices. eCryptfs to encrypt file systems, including home directories and, PAM integration, plain dm-crypt and EncFS. DNS and cryptography DNSSEC and DANE. BIND as an authoritative name server serving DNSSEC secured zones. BIND as an recursive name server that performs DNSSEC validation, KSK, ZSK, Key Tag, Key generation, key storage, key management and key rollover, Maintenance and resigning of zones, Use DANE. TSIG. Host Security Host Hardening BIOS and boot loader (GRUB 2) security. Disable useless software and services, sysctl for security related kernel configuration, particularly ASLR, Exec-Shield and IP / ICMP configuration, Exec-Shield and IP / ICMP configuration, Limit resource usage. Work with chroot environments, Security advantages of virtualization. Host Intrusion Detection The Linux Audit system, chkrootkit, rkhunter, including updates, Linux Malware Detect, Automate host scans using cron, AIDE, including rule management, OpenSCAP. User Management and Authentication NSS and PAM, Enforce password policies. Lock accounts automatically after failed login attempts, SSSD, Configure NSS and PAM for use with SSSD, SSSD authentication against Active Directory, IPA, LDAP, Kerberos and local domains, Kerberos and local domains, Kerberos tickets. FreeIPA Installation and Samba Integration FreeIPA, architecture and components. Install and manage a FreeIPA server and domain, Active Directory replication and Kerberos cross-realm trusts, sudo, autofs, SSH and SELinux integration in FreeIPA. Access Control Discretionary Access Control File ownership and permissions, SUID, SGID. Access control lists, extended attributes and attribute classes. Mandatory Access Control TE, RBAC, MAC, DAC. SELinux, AppArmor and Smack. etwork File Systems NFSv4 security issues and improvements, NFSv4 server and clients, NFSv4 authentication mechanisms (LIPKEY, SPKM, Kerberos), NFSv4 pseudo file system, NFSv4 ACLs. CIFS clients, CIFS Unix Extensions, CIFS security modes (NTLM, Kerberos), mapping and handling of CIFS ACLs and SIDs in a Linux system. Network Security Network Hardening FreeRADIUS, nmap, scan methods. Wireshark, filters and statistics. Rogue router advertisements and DHCP messages. Network Intrusion Detection ntop, Cacti, bandwidth usage monitoring, Snort, rule management, OpenVAS, NASL. Packet Filtering Firewall architectures, DMZ, netfilter, iptables and ip6tables, standard modules, tests and targets. IPv4 and IPv6 packet filtering. Connection tracking, NAT. IP sets and netfilter rules, nftables and nft. ebtables. conntrackd Virtual Private Networks OpenVPN server and clients for both bridged and routed VPN networks. IPsec server and clients for routed VPN networks using IPsec-Tools / racoon. L2TP.

LTE Architecture and Protocols course description This course provides a comprehensive tour of the LTE architecture along with services provided and the protocols used. What will you learn Describe the overall architecture of LTE. Explain the information flows through LTE. Describe the LTE security. Describe LTE mobility management. Recognise the next steps for LTE. LTE Architecture and Protocols course details Who will benefit: Anyone working with LTE. Prerequisites: Mobile communications demystified Duration 3 days LTE Architecture and Protocols course contents Introduction History, LTE key features. The 4G ITU process. The LTE 3GPP specifications. Specifications. System Architecture LTE hardware architecture. UE architecture and capabilities. E-UTRAN and eNB. EPC, MME functions, SGW, PGW and PCRF. System interfaces and protocol stacks. Example information flows. Dedicated and default bearers. EMM, ECM, RRC state diagrams. Radio transmission and reception OFDMA, SC-FDMA, MIMO antennas. Air interface protocol stack. Logical, transport and physical channels. Frame and slot structure, the resource grid. Resource element mapping of the physical channels and signals. Cell acquisition, data transmission and random access. MAC, RLC, PDCP protocols. LTE spectrum allocation. Power-on procedures Network and cell selection. RRC connection establishment. Attach procedure, including IP address allocation and default bearer activation. LTE detach procedure. Security in LTE networks LTE security features, identity confidentiality, ciphering and integrity protection. Architecture of network access security in LTE. Secure key hierarchy. Authentication and key agreement procedure. Security mode command procedure. Network domain security architecture. Security associations using IKE and IPSec. Mobility management RRC_IDLE, RRC_CONNECTED. Cell reselection, tracking area updates. Measurement reporting. X2 and S1 based handovers. Interoperation with UMTS, GSM and non-3GPP technologies such as cdma2000. QoS, policy control and charging QoS in LTE, EPS bearers, service data flows and packet flows. The architecture and signalling procedures for policy and charging control. Data transport using GPRS, differentiated services and MPLS. Offline and online charging in LTE. Delivery of voice and text messages over LTE Difficulties and solutions for Voice over LTE. Architecture and call setup procedures for circuit switched fallback. Architecture, protocols and call setup procedures in IP multimedia subsystem. Enhancements in release 9 LTE location services. Multimedia broadcast / multicast service and MBSFN. Cell selection, commercial mobile alert service. LTE Advanced and release 10 Impact of carrier aggregation on LTE air interface. Enhanced MIMO processing on uplink and downlink. Relaying. Release 11 and beyond. OAM and self organising networks Operation, administration, maintenance and provisioning for LTE. Self-configuration of base station parameters. Fractional frequency re-use, inter-cell interference co-ordination. Self-optimisation of base station procedures. Self-healing to detect and recover from faults.

This day will introduce you to the basic techniques and skills involved in doing graphic facilitation. Learn how to use a BIG piece of paper and a handful of pens to create a memorable summary of your training day, team meeting or your work with young people and families. Learn how to harvest the essence of an event in a visual representation. This is a ‘hands on’ interactive day built around demonstrations of graphic facilitation, coaching and the chance to try things out. Ideal for teams who can then go on together to practice, practice, practice. Learning Objectives To introduce you to the basic skills of graphic facilitation – no previous experience is needed To develop your capacity to ‘listen under the words’ and draw out the deeper messages To help you suspend your self-doubt – “I can’t draw!” and rediscover your capacity to create an effective visual representation of a meeting/training day/conversation etc Course Content The day will introduce you to the fundamentals of graphic facilitation and will include the following topics: Pens, Pastels and Paper – what you will need to get started The basic ‘grammar’ of graphic facilitation; the essential shapes, using colour, images, lettering, words, creating connection How to listen for the essence of what is being said and translate this into visual language A chance to do it live – with coaching

Introducing Therapy for Retroactive Jealousy Package: Overcoming Intrusive Thoughts and Fostering Emotional Well-being Are you struggling with retroactive jealousy, finding it difficult to cope with intrusive thoughts and emotions related to your partner’s past relationships? Miss Date Doctor’s Therapy for Retroactive Jealousy Package offers you expert support and guidance to overcome jealousy and foster emotional well-being in your current relationship. Retroactive jealousy is an emotional challenge that can cause distress and strain in relationships. Our experienced therapists are dedicated to helping you understand and manage these feelings, allowing you to build a healthier and more trusting connection with your partner. Here’s how the Therapy for Retroactive Jealousy Package can support you: Understanding Retroactive Jealousy: Our therapists will help you gain insights into the root causes of retroactive jealousy and its impact on your emotional well-being. Coping Strategies: We’ll equip you with effective coping strategies to manage intrusive thoughts and emotions, helping you reduce anxiety and distress. Building Self-Confidence: Therapy for retroactive jealousy can assist in building self-confidence and self-assurance, allowing you to feel more secure in your relationship. Effective Communication: We’ll guide you in improving communication with your partner about your feelings, fostering understanding and emotional connection. Developing Trust: Therapy will focus on rebuilding trust in your relationship, addressing any underlying issues that may contribute to feelings of jealousy. Letting Go of the Past: Our therapists will assist you in processing and letting go of obsessive thoughts related to your partner’s past. Positive Mindset: We’ll work towards cultivating a positive mindset, encouraging you to focus on the present and future rather than dwelling on the past. Embracing Emotional Intimacy: Therapy for retroactive jealousy can help you and your partner cultivate emotional intimacy and strengthen your bond. The Therapy for Retroactive Jealousy Package at Miss Date Doctor is designed to empower you to overcome jealousy and create a more fulfilling and trusting relationship. Our caring therapists provide a safe and supportive space to explore your feelings and concerns, allowing you to work towards emotional healing and a stronger connection with your partner. Invest in your emotional well-being and take the first step towards overcoming retroactive jealousy with the Therapy for Retroactive Jealousy Package. Embrace the opportunity to foster a more secure and loving relationship, free from the burden of intrusive thoughts and jealousy. Let our experienced therapists guide you towards a brighter and more emotionally fulfilling future. 3 x 1 hour sessions https://relationshipsmdd.com/product/therapy-for-retroactive-jealousy/

In this course we explore how we have attempted to build inclusive circles of support around individuals and contrast this with a radical approach to hospitality and community building – the Community Circle. The purpose of community circles is to bring people from a local community together to share their skills, talents, gifts and resources. This idea is based upon the premise that ALL of us need three things in our lives to make us happy and fulfilled: these are money, friendship and meaning. We believe that everyone needs community, everyone needs to be heard and everyone needs to have fun. Online Course now available via Teachable Platform – Creating Community Circles Learn at your own pace… lots of text and video support Category Inclusion Peer Support Parents and Carers   Description  Building Community Circles In this course we explore how we have attempted to build inclusive circles of support around individuals and contrast this with a radical approach to hospitality and community building – the Community Circle. The purpose of community circles is to bring people from a local community together to share their skills, talents, gifts and resources. This idea is based upon the premise that ALL of us need three things in our lives to make us happy and fulfilled: these are money, friendship and meaning. We believe that everyone needs community, everyone needs to be heard and everyone needs to have fun. Community Circles are based upon reciprocity and the assumption that EVERYONE has both gifts and needs – whether these are labelled or not. The circles adopt the fundamental value of inclusion that ‘all means all’, no one is excluded from community circles, instead the circle members work out how to include everyone equally and safely. A community circle is made up of participants and allies from the local community. The meeting starts with everyone sharing food and conversations. Next the group comes together in a circle so that everyone can see each other and shares what is good and new in their lives, everyone gets a turn to be listened to. ‘New and Good’ breaks the habit of thinking about and acting from what’s wrong, it is an exercise of giving and receiving attention with one another and it also provides a strong foundation of strengths from which we can think about and tackle difficulties. The group is then asked the question what do they want, need or have to offer. Community circles provide a great foundation or starting point from which to explore connections, build relationships, locate resources and share skills. These circles will be a particularly important resource for Brokers and the people that they work for. They provide a safe forum in which people can meet and friendships can start, a natural reservoir of people and relationships where people can be invited to offer their time and capacity. To be successful we have to start from a belief in inclusion. A belief that: 1 We are all born ‘in’. 2 All means all. 3 Everyone needs to belong. 4 Everyone is ready. 5 Everyone needs support. 6 Everyone can communicate. 7 Everyone can contribute. 8 Together we’re better. Learning Objectives For participants to learn how to create a Community Circle. For participants to understand the underlying rationale and ethos of this way of working. To explore ways of maximising an individual’s inclusion and connection with the wider community. To explore ways of helping with friendship, social connection and education. To increase confidence, social skills and presence of disabled adults and those with a wide range of need in their local community by focusing on their contribution. Who Is It For? Anyone interested in mobilising the community to make it more inclusive around disabled or challenging individuals. Course Content Understanding ordinary needs – plus the true dimensions of social inclusion Building relationships Creating natural circles of support Creating a community circle If you like this you will almost certainly enjoy: Person Centred Planning using PATH and MAPS