ºÝºÝߣ

ºÝºÝߣShare a Scribd company logo

Tc basics

?Download as PPTX, PDF?
?
J
jeromy fu

An introduction on tc basic concepts and the common used parameters. Shows how parameters are used in tbf internally.

1 of 37
Downloaded 118 times
Dive into TC ¨C TC basics Jeromy Fu
Agenda ? What¡¯s TC ? How it works ? Basic concepts ? Command and parameters
What¡¯s TC ? TC is abbr. of Traffic Control - Rate control - Bandwidth management - Active Queue Management(AQM) - Network Emulator, pkt loss, pkt disorder, pkt duplication, pkt delay - QoS ( diffserv + rsvp ) - Many more ¡­
What¡¯s tc ? user-level utilities iproute2( iproute2/tc ) ? tc kernel (linux/net/sched)
How it works
How it works
Basic concepts- Qdisc ? Qdisc(Queue discipline) - Decide which ones to send first, which ones to delay, and which ones to drop - class/classful Qdisc: Qdisc with/without configurable internal subdivision ? Naming convention: - Kernel: sch_*.c (sch_netem.c, sch_tbf.c ) - iproute2: q_*.c (q_netem.c, q_tbf.c)
Qdisc list ? Class Based Queueing (CBQ) ? Hierarchical Token Bucket (HTB) ? Hierarchical Fair Service Curve (HFSC) ? ATM Virtual Circuits (ATM) ? Multi Band Priority Queueing (PRIO) ? Hardware Multiqueue-aware Multi Band Queuing (MULTIQ) ? Random Early Detection (RED) ? Stochastic Fairness Queueing (SFQ) ? True Link Equalizer (TEQL) ? Token Bucket Filter (TBF) ? Generic Random Early Detection (GRED) ? Differentiated Services marker (DSMARK) ? Network emulator (NETEM) ? Deficit Round Robin scheduler (DRR) ? Ingress Qdisc
Basic concepts- Classification ? Classification(Filter) - Used to distinguish among different classes of packets and process each class in a specific way. ? Naming convention: - Kernel: cls_*.c (cls_u32.c, cls_rsvp.c ) - iproute2: f_*.c (f_u32.c, f_rsvp.c)
Classification list ? Elementary classification (BASIC) ? Traffic-Control Index (TCINDEX) ? Routing decision (ROUTE) ? Netfilter mark (FW) ? Universal 32bit comparisons w/ hashing (U32) ? IPv4 Resource Reservation Protocol (RSVP) ? IPv6 Resource Reservation Protocol (RSVP6) ? Flow classifier ? Control Group Classifier ? Extended Matches ? Metadata ? Incoming device classification
Basic concepts- Action ? Action Actions get attached to classifiers and are invoked after a successful classification. They are used to overwrite the classification result, instantly drop or redirect packets, etc. Works on ingress only. ? Naming convention: - Kernel: act_*.c (act_police.c, act_skbedit.c ) - iproute2: m_*.c (m_police.c, m_pedit.c)
Action list ? Traffic Policing ? Generic actions ? Probability support ? Redirecting and Mirroring ? IPtables targets ? Stateless NAT ? Packet Editing ? SKB Editing
Basic concepts- Class ? Classes either contain other Classes, or a Qdisc is attached ? Qdiscs and Classes are intimately tied together
TC Commands ? OPTIONS: options are effective for all sub commands ? OBJECTS: the object of the tc command operates on ? COMMAND: the sub command for each object
TC Commands
TC Qdisc ? Operations on qdisc: add | del | replace | change | show ? Handle: qdisc handle used to identify qdisc ? root|ingress|parent CLASSID, specify the parent node
qdisc handle ? Qdisc handle is used to identify Qdisc - {none|major[:]} - none is TC_H_UNSPEC - major is 16bits HEX number(Without ¡®0x¡¯ prefix) - : is optional ? Internally, qdisc_handle = major<<16
classid ? Classid is used to identify Class - {none|root|[major]:minor} - none is TC_H_UNSPEC, root is TC_H_ROOT - major/minor are both 16bits HEX numbers(Without ¡®0x¡¯ prefix), major is optional ? Internally, classid = (major<<16)|minor
stab and rtab ? stab is Size table, rtab is rate table. ? They¡¯re used to speed up the calculation of the transmit time of packets. ? The packet size is aligned to a predefined size in the stab slot. ? Then the rtab is used to give the pre- calculated time of the aligned packet size.
Linklayer ? Link layer affects packet size, if linklayer is set, both mpu and overhead must also be set
Linklayer
stab internal ? szopts: stab relating specifications, some are specified by the command, some are calculated ? data: the size table.
stab internal - user space ? Averagely distribute(*2) the MTU size into size table which has tsize slots
stab internal - kernel
rtab internal - user space ? rtab size is constantly 256
rtab internal - kernel
Measure units ? Rate
Measure units ? Size
Measure units ? time
TC Class ? Tc class can only be applied for classful qdisc, such as htb, cbq etc
example ? TBF ? HTB
tbf ? limit/latency ? buffer/burst/maxburst, capcity of token bucket: size[/cell] ? mpu: minimum process unit ? rate/peakrate ? Max(Rate/HZ,MTU)
tbf - user space ? latency convert to limit finally
tbf - user space ? rtab initialization
tbf - kernel
tbf - kernel
Tbf dequeue

More Related Content

Tc basics

  • 1. Dive into TC ¨C TC basics Jeromy Fu
  • 2. Agenda ? What¡¯s TC ? How it works ? Basic concepts ? Command and parameters
  • 3. What¡¯s TC ? TC is abbr. of Traffic Control - Rate control - Bandwidth management - Active Queue Management(AQM) - Network Emulator, pkt loss, pkt disorder, pkt duplication, pkt delay - QoS ( diffserv + rsvp ) - Many more ¡­
  • 4. What¡¯s tc ? user-level utilities iproute2( iproute2/tc ) ? tc kernel (linux/net/sched)
  • 7. Basic concepts- Qdisc ? Qdisc(Queue discipline) - Decide which ones to send first, which ones to delay, and which ones to drop - class/classful Qdisc: Qdisc with/without configurable internal subdivision ? Naming convention: - Kernel: sch_*.c (sch_netem.c, sch_tbf.c ) - iproute2: q_*.c (q_netem.c, q_tbf.c)
  • 8. Qdisc list ? Class Based Queueing (CBQ) ? Hierarchical Token Bucket (HTB) ? Hierarchical Fair Service Curve (HFSC) ? ATM Virtual Circuits (ATM) ? Multi Band Priority Queueing (PRIO) ? Hardware Multiqueue-aware Multi Band Queuing (MULTIQ) ? Random Early Detection (RED) ? Stochastic Fairness Queueing (SFQ) ? True Link Equalizer (TEQL) ? Token Bucket Filter (TBF) ? Generic Random Early Detection (GRED) ? Differentiated Services marker (DSMARK) ? Network emulator (NETEM) ? Deficit Round Robin scheduler (DRR) ? Ingress Qdisc
  • 9. Basic concepts- Classification ? Classification(Filter) - Used to distinguish among different classes of packets and process each class in a specific way. ? Naming convention: - Kernel: cls_*.c (cls_u32.c, cls_rsvp.c ) - iproute2: f_*.c (f_u32.c, f_rsvp.c)
  • 10. Classification list ? Elementary classification (BASIC) ? Traffic-Control Index (TCINDEX) ? Routing decision (ROUTE) ? Netfilter mark (FW) ? Universal 32bit comparisons w/ hashing (U32) ? IPv4 Resource Reservation Protocol (RSVP) ? IPv6 Resource Reservation Protocol (RSVP6) ? Flow classifier ? Control Group Classifier ? Extended Matches ? Metadata ? Incoming device classification
  • 11. Basic concepts- Action ? Action Actions get attached to classifiers and are invoked after a successful classification. They are used to overwrite the classification result, instantly drop or redirect packets, etc. Works on ingress only. ? Naming convention: - Kernel: act_*.c (act_police.c, act_skbedit.c ) - iproute2: m_*.c (m_police.c, m_pedit.c)
  • 12. Action list ? Traffic Policing ? Generic actions ? Probability support ? Redirecting and Mirroring ? IPtables targets ? Stateless NAT ? Packet Editing ? SKB Editing
  • 13. Basic concepts- Class ? Classes either contain other Classes, or a Qdisc is attached ? Qdiscs and Classes are intimately tied together
  • 14. TC Commands ? OPTIONS: options are effective for all sub commands ? OBJECTS: the object of the tc command operates on ? COMMAND: the sub command for each object
  • 16. TC Qdisc ? Operations on qdisc: add | del | replace | change | show ? Handle: qdisc handle used to identify qdisc ? root|ingress|parent CLASSID, specify the parent node
  • 17. qdisc handle ? Qdisc handle is used to identify Qdisc - {none|major[:]} - none is TC_H_UNSPEC - major is 16bits HEX number(Without ¡®0x¡¯ prefix) - : is optional ? Internally, qdisc_handle = major<<16
  • 18. classid ? Classid is used to identify Class - {none|root|[major]:minor} - none is TC_H_UNSPEC, root is TC_H_ROOT - major/minor are both 16bits HEX numbers(Without ¡®0x¡¯ prefix), major is optional ? Internally, classid = (major<<16)|minor
  • 19. stab and rtab ? stab is Size table, rtab is rate table. ? They¡¯re used to speed up the calculation of the transmit time of packets. ? The packet size is aligned to a predefined size in the stab slot. ? Then the rtab is used to give the pre- calculated time of the aligned packet size.
  • 20. Linklayer ? Link layer affects packet size, if linklayer is set, both mpu and overhead must also be set
  • 22. stab internal ? szopts: stab relating specifications, some are specified by the command, some are calculated ? data: the size table.
  • 23. stab internal - user space ? Averagely distribute(*2) the MTU size into size table which has tsize slots
  • 24. stab internal - kernel
  • 25. rtab internal - user space ? rtab size is constantly 256
  • 26. rtab internal - kernel
  • 30. TC Class ? Tc class can only be applied for classful qdisc, such as htb, cbq etc
  • 32. tbf ? limit/latency ? buffer/burst/maxburst, capcity of token bucket: size[/cell] ? mpu: minimum process unit ? rate/peakrate ? Max(Rate/HZ,MTU)
  • 33. tbf - user space ? latency convert to limit finally
  • 34. tbf - user space ? rtab initialization