Cdn And Networking Review

Front 1

A CDN (content distribution network) keeps copies of data _________, which has the effect of _________________

Back 1

- close to those who will be downloading it

- freeing backbone capacity (less data needs to be routed on lines between ISPs) and lowering delivery costs

Front 2

A CDN accelerates delivery of __________

Back 2

Web pages, audio, video and other Internet-based content to users around the world.

Front 3

The CDN replicates the content provider's files in servers, called __________ or _________ located in geographically dispersed datacenters.

Back 3

"caching servers" or "edge servers"

Front 4

Most CDNs are ________; however, large companies may develop their own.

Back 4

third-party services

Front 5

Replicated content is delivered to users with greater ___________.

Back 5

speed and reliability.

Front 6

CDNs are often connected to multiple ___________ and have ______________ with others, providing high availability to users.

Back 6

ISP backbones; peering relationships

Front 7

Product lifecycle:

Back 7

Introduction
Growth
Maturity
Saturation and decline

Front 8

A CDN provides for web acceleration because of its __________

Back 8

multiple backbone, numerous caching servers, compression between nodes.

Front 9

A CDN may offer all popular streaming methods such as ______________

Back 9

Flash, Windows Media, Silverlight and progressive download, the latter using the same HTTP protocol as Web pages.

Front 10

The CDN may offer server-side processing of ____________

Back 10

Java and ASP scripts.

Front 11

If the CDN does not provide server-side processing, that operation takes place _____________

Back 11

in the customer's servers, and the CDN can deliver the accompanying graphics or other downloads.

Front 12

CDN - Progressive download

Back 12

- A method for streaming non-live video to the user for immediate playback.
- Like any other HTTP download from a Web site rather than streaming downloads from a streaming server. These sites use free, open source Web server software.
- Highly favored delivery method, including Google's YouTube.
- Early problems were inability to fast-forward (fixed by enhancing CDN servers) and downloading whole file even if user did not use it.
- May be set up to allow a quality choice: can opt for higher quality on a slow connection - the video will halt at various stages waiting for more content, but quality will be high.

Front 13

True streaming (not progressive download)

Back 13

- relies on the server side to detect the user's connection speed and select the file with the appropriate encoding rate for smooth, uninterrupted playback.
- uses expensive, proprietary software.

Front 14

IP Transit

Back 14

- Buying a large pipe (10G+) to a major Internet provider (e.g. L3 (IP wholesalers), Cogent, Global Crossing, AT&T)
- Transit charges are line access charges
- Deliver content over TCP & UDP
- Equinix is an IP Transit broker / arbiter, has colos

Front 15

Transport

Back 15

- P2P, not accessible to/from Internet
- "Transport" which is a point to point link that is not accessible to or from the internet. It is used to connect two sites to each other. You can also order transport links from most transit providers.

Front 16

Peering

Back 16

- An interconnection agreement between two companies (ISPs), avoiding high cost of IP Transit
- The exchange and updating of router info (typically w/BGP - boarder gateway protocol)
- Public peering - Interconnection utilizing a multi-party shared switch fabric such as an Ethernet switch
- Private peering - Interconnection utilizing a point-to-point link between two parties
- Public peering is layer 2 (switches); private peering is layer 1 or 2
- Done at Internet eXchange Points (IXs / IXPs) & regional switching points
- Some larger ISPs have their own backbone network - they use peering to reach regional endpoints
- The intertwined peering arrangements are a substantial part of the Internet

Front 17

IXP = IX = Internet eXchange Point

Back 17

- Where ISPs can exchange info w/o using expensive transit from upstream providers
- Historically called NAPs (Network Access Points)
- Some span multiple collocation facilities (colos) around the world, that host public and private peering

Front 18

Example colo company: Equinix (an IP Transit broker / arbiter, has colos)

Back 18

- Foster City, CA, and worldwide
- Switched IP connectivity service (S-IPC)
- Competitors include TelX and Peer
- One stop shop for bandwidth requests for collocation customers
- Usage based and volume based options available
- Services include:
- IP address allocation
- Availability SLA
- Primary / secondary DNS
- Redundancy on physical, transmission, & IP layers
- Redundant fiber and hardware and backup power

Front 19

Fast Ethernet =

Back 19

twisted pair, max 100Mbps

Front 20

Gigabit Ethernet =

Back 20

1Gbps, fiber or can be accommodated on Cat5, Cat5e, Cat6, as of 2009; 10Gbps Ethernet is replacing 1Gbps in backbone networks and even works over copper up to 10G!

Front 21

Number names

Back 21

kilo mega giga tera peta exa
deci centi milli micro nano pico femto atto

Front 22

Scrum

Back 22

an iterative, incremental framework for agile software development.

Front 23

Spanning tree protocol (STP)

Back 23

a network protocol that ensures a loop-free topology for any bridged LAN. It prevents bridge loops and ensures broadcast radiation. As the name suggests, it creates a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches), and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes. It includes redundant links to provide automatic backup paths if an active link fails. Bridge loops must be avoided because they result in flooding the network.

Front 24

TCP/IP - Internet protocols

Back 24

IPv4 = 32 bits
IPv6 = 128 bits

Front 25

OSI 7 layer model

Back 25

- Layer 1, physical, includes cables and repeaters
- Layer 2, data link layer, known as bridging, switches are here, is for LAN (MAC addresses) & WAN
- Layer 3, network layer, addressing (IP) and routing protocols, for Internet and intranets
- Layer 4, transport layer, breaks down large files into smaller segments that are less likely to be corrupted, and reassembles them on the receiving end
- Layer 5, Session
- Layer 6, Presentation
- Layer 7, Application

Front 26

ITIL

Back 26

Structured way of managing IT org (change management like we did at Amdocs with RFCs, also can include business process mgt, but at Amdocs we used CMMI (level 3) and ISO)

Front 27

IBX

Back 27

- IBX = Internet Business Exchange
- i.e. colos like Equinix and such

Front 28

How is transit distinct from peering?

Back 28

In peering only traffic between the two ISPs and their downstream customers is exchanged and neither ISP can see upstream routes over the peering connection.

Peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the customers of each network.

Peering requires physical interconnection of the networks, an exchange of routing information through the Border Gateway Protocol (BGP) routing protocol and is often accompanied by peering agreements of varying formality, from "handshake" to thick contracts.

Front 29

QoS - Quality of Service

Back 29

- In the field of computer networking and other packet-switched telecommunication networks, QoS refers to resource reservation control mechanisms rather than the achieved service quality.
- QoS is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. ..important especially for real-time streaming multimedia applications such as voice over IP, online games and IP-TV, since these often require fixed bit rate and are delay sensitive.
- An alternative to complex QoS control mechanisms a best-effort network that over-provisions capacity so that it is sufficient for the expected peak traffic load.
- QoS is sometimes used as a quality measure, with many alternative definitions. Quality of service sometimes refers to a guaranteed service quality. High QoS is often confused with a high level of performance or achieved service quality, for example high bit rate, low latency and low bit error probability.
- Types of problems: Throughput (Bandwidth), Dropped packets, Delay (Latency), Jitter (from packet arriving with different amounts of delay), Out-of-order delivery, Error

Front 30

What is an ASP?

Back 30

- An application service provider (ASP) is a business that provides computer-based services to customers over a network.

- Software offered using an ASP model is also sometimes called On-demand software or software as a service (SaaS).

- Most CDNs are operated as an application service provider (ASP) on the Internet, although an increasing number of Internet network owners, such as AT&T, are building their own CDN to improve on-net content delivery and to generate revenues from content customers.

Types of ASPs:
- A specialist or functional ASP delivers a single application, such as credit card payment processing or timesheet services
- A vertical market ASP delivers a solution package for a specific customer type, such as a dental practice
- An enterprise ASP delivers broad spectrum solutions
- A local ASP delivers small business services within a limited area

Front 31

ISPs

Back 31

Internet Service Providers - sample list:
- America Online (AOL) - offers services such as Internet access, email account, instant messaging, chat, and other online features.
- British Telecom (BT) - provides telecommunication services, including long-distance and international calls. Also manages private networks and supplies mobile communication services.
dir.yahoo.com/.../Telecommunications/British_Telecom__BT_
- EarthLink (Nasdaq:ELNK) - provides dial-up, DSL, cable modem, and satellite Internet services.
- Juno - free email account and Internet access.
- Cogent Communications - Optical ISP delivering high speed Internet access and transport services to businesses in large multi-tenant buildings.
- AT&T Yahoo! DSL - Log in to AT&T (formerly SBC) Yahoo! DSL Internet services and access a customizable Web experience. Formerly known as SBC Yahoo!

Front 32

BGP - Border Gateway Protocol - overview

Back 32

- BGP is the core routing protocol of the Internet and is fully decentralized routing

- It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). BGP neighbors, or peers, are established by manual configuration between routers to create a TCP session on port 179. (among routing protocols, BGP is unique in using TCP as its transport protocol).

- it is a path vector protocol: BGP does not use traditional Interior Gateway Protocol (IGP) metrics, but makes routing decisions based on path, network policies and/or rulesets

Front 33

BGP - EBGP & IBGP

Back 33

When BGP is running inside an autonomous system (AS), it is referred to as Internal BGP (IBGP or Interior Border Gateway Protocol). When it runs between autonomous systems, it is called External BGP (EBGP or Exterior Border Gateway Protocol). Routers on the boundary of one AS, exchanging information with another AS, are called border or edge routers.

An autonomous system with internal BGP (IBGP) must have all of its IBGP peers connect to each other in a full mesh (where everyone speaks to everyone directly). This full-mesh configuration requires that each router maintain a session to every other router. In large networks, this number of sessions may degrade performance of routers, due either to a lack of memory, or too much CPU process requirements.

Front 34

BGP - growth and instability of the Internet routing table

Back 34

One of the largest problems faced by BGP, and indeed the Internet infrastructure as a whole, is the growth of the Internet routing table.
- larger routing tables take longer to stabilize
- as of January, 2009, the routing table has approximately 300,000 entries

Front 35

BGP - Load-balancing problem

Back 35

- Another factor causing this growth of the routing table is the need for load balancing of multi-homed networks

- It is not a trivial task to balance the inbound traffic to a multi-homed network across its multiple inbound paths, due to limitation of the BGP route selection process. Like most other routing protocols, the BGP protocol does not detect congestion.

- To work around this problem, BGP administrators of that multihomed network may divide a large continuous IP address block into smaller blocks, and tweak the route announcement to make different blocks look optimal on different paths.. Such cases will increase the number of routes as seen on the global BGP table (multihoming also provides better redundancy either to multiple access points of a single ISP or to multiple ISPs).

Front 36

7 Layer OSI Model

Back 36

Application
Presentation
Session
Transport (TCP)
Network (IP / routers)
Data link (Mac addresses - switches)
Physical (cables / repeaters / modems)