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| -rw-r--r-- | qos/ip-qos.mgp | 395 | ||||
| -rw-r--r-- | qos/qos-1.eps | 611 | ||||
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diff --git a/qos/abstract b/qos/abstract new file mode 100644 index 0000000..770c363 --- /dev/null +++ b/qos/abstract @@ -0,0 +1,23 @@ +Quality of Service in IP Networks + +IP networks were designed some 25 years ago. Networks based on TCP/IP are +widely deployed, as organization-local Intranets as well as in the Internet +itself. The usage patterns of those networks change. Especially new +technologies like voice-over-IP as well as streaming multimedia applications +have different requirements on the underlying network infrastructure than +bulk data transfers like ftp/www or interactive traffic like telnet/ssh. + +Organizations usually run a mixture of different services on their Internet +uplinks or on their organization-internal wide area networks. Bandwidth is +usually a limited ressource, so everybody wants to divide bandwidth between +different services according to his specific needs. + +Linux always had a very strong focus on network functionality and has +sophisticated means for bandwidth control / QoS since Kernel 2.2. + +The presentation is organized in the following parts: + Basics of QoS in IP networks + How can Linux help with QoS + Sample scenarios of Linux-based QoS solutions + Overview about advanced conecpts (DiffServ, IntServ, RSVP, ...) + diff --git a/qos/ip-qos.mgp b/qos/ip-qos.mgp new file mode 100644 index 0000000..3960927 --- /dev/null +++ b/qos/ip-qos.mgp @@ -0,0 +1,395 @@ +%include "cnc-style.mgp" +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +%nodefault +%pcache 1 1 0 1 +%size 7, font "standard", fore "white", vgap 20, back "black" +%bimage "fundo-cnc.png" 1024x768 + +%center +%size 7 + + +Quality of Service in IP Networks + +%center +%size 4 +by + +Harald Welte <laforge@conectiva.com> + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Contents + + Definition of QoS + + Why QoS + + IP Networks are not designed for QoS + + How to do the impossible + + What can Linux based systems help + + Advanced Concepts (DiffServ, IntServ, RSVP, ...) + + References / Further Reading + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Definiton of QoS + + Provide Service Differentiation + + Performance Assurance by + + Bandwitdh guarantees + for streaming multimedia traffic + priorizing certain important applications + + Latency guarantees + for voice over IP + for interactive character-oriented applications (ssh,telnet) + + Packet-loss guarantees + for unreliable layer-4 protocols + to avoid retransmits + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Why QoS + + + Decide how and who available bandwidth is devided + + Limit available bandwidth for certain users / applications + + Guarantee bandwidth for certain users / applications + + Divide bandwidth more equally between users / applications + + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +IP networks not designed for QoS + + +Properties of IP-based networks: + + offer a "best-effort" service + + make NO guarantees about + bandwidth + latency + packet loss + + provide a non-reliable packet transport + +Conclusion: IP networks are not suitable for QoS + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +How to do the Impossible + +%size 4 + +As IP Networks including Hardware (Routers, ...) are widely deployed, all QoS efforts have to layer on top of the existing technology. + + There's no real solution to control latency + latency widely dependent on routing, which may be dynamic + + There's no real solution to control packet loss + packet loss may occurr on any intermediate router + + But we can control bandwidth usage! + The sender can limit bandwidth for outgoing streams + Intermediate routers BEFORE a bottleneck can control bandwidth usage + +%size 5 + + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +What can Linux systems do? + + Bandwidth limiting at the sender application + not many applications support it + server often out of control (on Internet, ...) + server doesn't know what's between him and the client + + Bandwidth control on intermediate router before bottleneck + Ideal case because this is where packet loss would occurr + Sophisticated queue scheduling on the outgoing queue + Variety of different queue scheduling algorithms + + Flow throttling at the Receiver + Worst case, because influence is limited + Theoretically possible for TCP, no implementation yet. + Ingress qdisc might help + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Bandwidth limiting at server + + Some Internet Servers support bandwidth limiting + + ProFTPd (builtin support) + + Apache (using contributed mod_bandwidth) + + + Using those features it is easy to limit + + maximum bandwidth used per connection + + maximum bandwidth used per client (IP/network) + + maximum bandwidth used by one virtual host (webserver/ftpserver) + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Router before bottleneck + +%size 4 + +The router receives more packets on his incoming interface(s) than it can send out on the outgoing interface. It has to build a queue of packets (usually a FIFO one) and starts dropping packets as soon as the queue is full + +%image "qos-1.png" 0 100 30 + +The idea is to change this queue, thus decide + which packets get enqueued in which order + how many packets get queued + which packets get dropped in case of a filling queue + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +The Linux 2.2 / 2.4 Solution + + Packet Scheduling algorithms in the Kernel + CBQ - Class Based Queue + RED - Random Early Drop + SFQ - Stochastic Fairness Queueing + TEQL - True Link Equalizer + TBF - Token Bucket Filter + + tc command of iproute2 package for configuration + almost no documentation + very few examples on the internet + + Packet Classification + tc builtin classes (route, u23, ...) + all iptables/netfilter matches by using fwmark + +Conclusion: Linux is the best suited general-purpose operating system for QoS, but almost nobody is using it because lack of knowledge. + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Available queuing algorithms + + CBQ - Class Based Queue + hierarchical bandwidth classes + used as basis in almost all cases + TBF - Token Bucket Filter + really accurate algorithm + uses a lot of CPU + not possible for high bandwidth links (>1MBit) + SFQ - Stochastic Fairness Queueing + less accurate algorithm + tries to distinguish between individual streams + does round robin between those streams + TEQL - True Link Equalizer + allows to 'bundle' interfaces + RED - Random Early Detect / Drop + simulates congested link by statistic packet dropping + uses almost no CPU + recommended for high-bandwidth backbones + others (WRR, TCINDEX, DSMARK, ..) + WRR not officially included in kernel, similar to CBQ + others mostly used for DiffServ + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +The big picture + +Overview of the a packet's journey + +%size 3 +%font "typewriter" + Incoming Packets +%size 3 +%font "typewriter" + | +%size 3 +%font "typewriter" + V +%size 3 +%font "typewriter" + Packet Classification classify +%size 3 +%font "typewriter" + (ipchains/iptables) set nfmark +%size 3 +%font "typewriter" + | +%size 3 +%font "typewriter" + V +%size 3 +%font "typewriter" + Routing decision +%size 3 +%font "typewriter" + | +%size 3 +%font "typewriter" + V +%size 3 +%font "typewriter" + TC filter select classes based on nfmark +%size 3 +%font "typewriter" + / | \ +%size 3 +%font "typewriter" + / | \ +%size 3 +%font "typewriter" + / | \ +%size 3 +%font "typewriter" +Different Bandwidth classes bandwidth classes (CBQ) +%size 3 +%font "typewriter" + \ | / +%size 3 +%font "typewriter" + \ | / +%size 3 +%font "typewriter" + \ | / +%size 3 +%font "typewriter" + Enqueuing output queue discipline +%size 3 +%font "typewriter" + | +%size 3 +%font "typewriter" + V +%size 3 +%font "typewriter" + Outgoing packets + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Example scenario usin CBQ + +%size 4 +Let's assume we have a link with 10 MBit maximum available bandwidth. +We offer two major services to the outside world: Anonymous FTP and a Webserver offering important Information. + +FTP Bulk data transfers are using up almost all available bandwidth, thus slowing down accesses to our website :( + +We want to have FTP transfers use up to 8MBit and reserve 2MBit for WWW. + +Implementation uses CBQ for bandwidth divisions. + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Example scenario + +%size 3 + attach a CBQ to the device +%size 3 +%font "typewriter" +tc qdisc add dev eth0 root handle 10: cbq + bandwidth 10Mbit avpkt 1000 + +%size 3 +%font "standard" + create CBQ classes +%size 3 +%font "typewriter" +tc class add dev eth0 parent 10:0 classid 10:1 cbq + bandwidth 10MBit rate 10MBit allot 1514 + weight 1Mbit prio 8 maxburst 20 avpkt 1000 + +tc class add dev eth0 parent 10:1 classid 10:100 cbq + bandwidth 10MBit rate 8MBit allot 1514 + weight 800kbit prio 5 maxburst 20 avpkt 1000 bounded + +tc class add dev eth0 parent 10:1 classid 10:200 cbq + bandwidth 10MBit rate 2MBit allot 1514 + weight 200kbit prio 5 maxburst 20 avpkt 1000 bounded + +%size 3 +%font "standard" + add filter rules +%size 3 +%font "typewriter" +tc filter add dev eth0 parent 10:1 protocol ip handle 6 fw classid 10:100 + +iptables -t mangle -A PREROUTING -j MARK -p tcp --sport 20 --set-mark 6 + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Further optimization + +%size 4 +Now we have achieved bandwidth division between two services. + +Within one service, however, one individual user with a high bandwith link can still use up most of our bandwidth, slowing down other user. + +We can improve this behaviour of changing the scheduling algorithm from it's default (fifo) + +%size 3 +%font "typewriter" +tc qdisc add dev eth0 parent 10:100 sfq quantum 1514b perturb 15 +tc qdisc add dev eth0 parent 10:200 sfq quantum 1514b perturb 15 + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%page +QoS in IP Networks +Further reading / Links + + Bandwidth limiting on Servers + ProFTPd + http://www.proftpd.net/ + Apache mod_bandwidth / mod_bwshare + ftp://ftp.cohprog.com/pub/apache/module/mod_bandwidth.c + http://www.topology.org/src/bwshare/ + + Queue scheduling + Advanced Routing HOWTO + http://www.ds9a.nl/2.4Routing/ + Linux QoS HOWTO + http://www.ittc.ukans.edu/~rsarav/howto/ + iproute2+tc + + This presentation + Authors Homepage + http://www.gnumonks.org/ diff --git a/qos/qos-1.eps b/qos/qos-1.eps new file mode 100644 index 0000000..21c5a00 --- /dev/null +++ b/qos/qos-1.eps @@ -0,0 +1,611 @@ +%!PS-Adobe-2.0 EPSF-2.0 +%%Title: /laforge/home/laforge/incoming/qos-1 +%%Creator: Dia v0.86 +%%CreationDate: Mon Apr 2 16:14:45 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