1. The Technology Behind Distance Working

2. academy@ ® Overview The modern enterprise may well have: –A data centre with multiple branch offices –Mobile workers either working from home or ‘on the road’ working at customer sites

3. academy@ ® Overview - 2 Increasing dependence on IP networks causes problems in three key areas: –User access to data centre resources (application, storage, etc) –Backup strategy (if multiple remote servers exist) –Communication (audio and visual) We will look at each of these in turn

4. academy@ ® Remote User Access Users at HQRemote User Access Data access is typically via switched ethernet B/W =100/1000 Mbps Negligible latency Data access will share the WAN bandwidth from a site B/W = 1 to a few 10s of Mbps Latency is typically 10s of ms (much worse if over satellite)

5. academy@ ® Limited Bandwidth The problems here are obvious: –Much slower file access –Remote offices may well now access the company phone network using VoIP –User experience will be different from those at the HQ –But not the whole picture!

6. academy@ ® High Latency Often overlooked TCP requires packet acknowledgements – high latency means time is wasted waiting for acknowledgements Layer 7 protocols (e.g. CIFS) are even more chatty! Many round trips across the WAN results in even more time being wasted Adding more bandwidth will not solve this problem

7. academy@ ® The Problem with Latency WAN

8. academy@ ® This is even worse for Satellite Networks Diameter of the Earth = 13,000 Km (approx) Speed of light, C = 300,000 Km/s Average round trip (very approx) = 150,000 Km Equates to ~500ms (0.5s) of latency!

9. academy@ ® Possible Solutions Local servers –Places applications and storage where the users are –BUT: Expensive Creates pools of storage – issues for backup and management File Servers Mail Servers Web Servers Filers Tape Backup Storage WAN File Servers Mail Servers Filers Tape Backup Data CenterBranch Office

10. academy@ ® Possible Solutions - 2 Install a high bandwidth link –An obvious, simple solution –BUT: Expensive Doesn’t solve latency issues 100 Mbps

11. academy@ ® Possible solutions - 3 Install a WAN Acceleration device – e.g. Riverbed Riverbed tackles the problem in three key areas: –Bandwidth –Latency issues associated with TCP –Latency issues associated with layer 7 protocols

12. academy@ ® How does Riverbed accelerate the bandwidth? Data WAN Reconstructed Files & Data Data Center Branch Office References New data

13. academy@ ® How does Riverbed deal with TCP latency? Window Scaling (RFC 1323) Virtual Window Expansion High-Speed and Maximum TCP Make TCP payload bigger 16KB to 100KB+ Repack payload with references From 100KB+ to Virtual 1MB+ References New data Data

14. academy@ ® How does Riverbed deal with latency issues at layer 7? The Steelheads understand certain application layer protocols and are able to perform certain transactions ahead of time, saving unnecessary WAN round trips – Transaction Prediction WAN DATA CENTER BRANCH OFFICE Optimized WAN Transfer Steelhead completes transaction locally Steelhead completes transaction locally

15. academy@ ® But what about users on the move? Riverbed Steelhead Mobile enables Mobile Client software to be installed which effectively creates a Virtual Steelhead which travels with the user Data Center Steelhead Mobile Controller WAN Planners on-site Engineers at home Small Offices Branch Offices Mobile Executives

16. academy@ ® Possible Solutions - 4 Implement Quality of Service (QoS) –Can prioritise key traffic and clients/servers to guarantee bandwidth and/or delay –Does not give any extra bandwidth but is used to ensure that bandwidth or delay sensitive traffic (e.g. VoIP) is not suppressed by other traffic Riverbed Steelheads can mark traffic for other QoS devices or can implement QoS enforcement directly Total bandwidth (100%) FTP (40%) Web (30%) VoIP (30%)

17. academy@ ® Backup Strategy For a consolidated environment not an issue –Data will be backed up centrally If you have local servers then these will need backing up –How will this fit into any existing backup strategy? –Where and how will be data be backed up? –How will backup media be managed?

18. academy@ ® Televaulting A scenario where data from remote sites are backed up over the WAN to a central server – the vault Simplifies backup strategy by removing the need for removable media at remote sites Data Centre Vault Branch office 1 Branch office 2

19. academy@ ® Example - Asigra Local servers WAN DS-System Web Portal DS-Operator BLM Archiver Windows DS-Client Linux DS- Client DS-User Incremental forever backups WAN data is compressed and encrypted Common File Elimination

20. academy@ ® Audio / Visual Communication Remote office communications are no longer just about data The use of networks has changed due to media with a resulting adaptation of the underlying technology Historically, media has been transferred using a ‘Store and Forward’ approach There is now an ever increasing use and demand for media to be transported in Real-Time

21. academy@ ® Voice over IP (VoIP) Increasingly, companies are starting to replace their analogue phone systems with VoIP technology Why? –Cost - Voice conversations require a relatively low bandwidth, comfortably carried on existing data networks –Flexibility – VoIP systems enable easy relocation of handsets should employees move or change location –Management Services – Can use control tools providing facilities such as security, forwarding, conferencing and storing data, often over a web-browser –Reporting – Can easily obtain and generate usage reports

22. academy@ ® How do you transfer audio packets over a network? Analogue sound, e.g. human speech needs converting into a digital signal and then coding into a format suitable for transport across a network This process will need reversing at the far end This process is the same for both audio and video

23. academy@ ® Analogue to Digital Conversion

24. academy@ ® But what about session setup? In legacy, analogue telephone networks a dedicated session or circuit was established - circuit switching IP is a packet switched protocol, therefore there needs to be a mechanism to setup and configure a session between users having a phone conversation. Two alternate protocols exist to accomplish this: –H.323 –SIP

25. academy@ ® H.323 - Overview ITU-T standard Key goals –Discovery and registration –Admission –Call set-up (H.225 -> Q.931) –Capability (H.245) –Availability –Location / addressing –Call Control –Services

26. academy@ ® H.323 Protocol Stack T.124 Physical Layer Link Layer Unreliable Transport (UDP) Reliable Transport (TCP) Network Layer (IP) Audio G.7XX Video H.26X Call Control H.245 Audio RTP Audio Control RTCP H.225.0 Call Signalling (Q.931) Q.931 Terminal Control and Management Data App AV App Control Terminal to Gatekeeper Signalling (RAS) T.123 T.125 T.124 Source: Voice Technologies

27. academy@ ® H.323 Architectural Overview Source: ITU H.323 Recommendation Terminal Router MCU TerminalRouter Gateway H.323 zone Terminal Router Gatekeeper

28. academy@ ® SIP Overview SIP stands for Session Initiation Protocol Based on HTTP/1.1 More lightweight than H.323 Supports personal mobility Handles –User location –User capability –User availability –Call setup –Call handling

29. academy@ ® SIP Architecture RedirectRegistrarDNS UAC UAS ProxyGateway Location Server

30. academy@ ® Example System - ISDN Gateway / Networker LifeSize Codec Gatekeeper MCU Call Manager Internet Paris Toronto Leeds Berlin Videoconferencing