Archive for the ‘autoqos’ tag
ONT Notes – AutoQoS
- AutoQoS benefits
- Automates QoS for most deployments
- Protects business-critical apps to maximize availability
- Simplifies QoS deployments
- Reduces configuration errors
- Cheaper, faster, and simpler deployments
- Follows DiffServ
- Allows complete control over QoS configs
- Allows modification of auto-generated configs
- AutoQoS phases of evolution
- AutoQoS VOIP – Early version that configures the basics without discovery
- AutoQoS for Enterprise – Second version that only runs on routers and uses two-step process
- Autodiscovery using NBAR
- Generation of class maps
- AutoQoS key elements
- Application classification
- Policy generation
- Configuration
- Monitoring and reporting
- Consistency
- Interfaces that you can configure AutoQoS on
- Serial ifs with PPP and HDLC
- FR point-to-point subifs (NOT multipoint)
- ATM point-to-point subifs
- FR-to-ATM links
- Prerequsites
- No Qos policy already configured on if
- CEF enabled on if
- Correct bandwidth configured on if
- IP address on low-speed if
- Configuring AutoQoS Enterprise on a router (NOT a switch)
- auto qos discovery – begins discovery process
- auto qos – generates and applies MQC-based policies
- Configuring AutoQoS VOIP
- auto qos voip [ trust | cisco-phone ]
- Verifying AutoQoS on router
- show auto discovery qos – get autodiscovery results
- show auto qos – examine configuration generated
- Number of classes
- Classification options
- Marking options
- Queuing mechanisms
- Other QoS mechanisms
- If, subif, PVC where policy is applied
- show policy-map interface – look at if stats
- Verify AutoQoS VOIP
- show auto qos
- show policy-map interface
- show mls qos maps – shows CoS to DSCP mappings
- Possible issues with AutoQoS
- Too many traffic classes – manually consolidate some
- Configuration doesn’t change – rerun AutoQoS
- Configuration may not fit your situation – fine-tune it by hand
- Fine-tuning AutoQoS
- Use QPM
- CLI
- copy policy into editor, change, reapply
- AutoQoS can match on characteristics besides ACLs and NBAR
- match input interface
- match cos
- match ip precedence
- match ip dscp
- match ip rtp
ONT Notes – Classification, Marking, and NBAR
Here’s another set of notes from my ONT studies. I’m sure someone will find it useful. Please help to correct dumbass mistakes.
- Classification is done with traffic desriptors
- Ingress interface
- CoS value on ISL or 802.1P frames
- Source/destination IP address
- IP Precedence or DSCP value
- MPLS EXP
- Application type
- Layer 3 QoS
- Type of Service (ToS) is 8-bit field.
- First 3 bits of ToS are the IP precedence.
- First 6 bits of ToS are the DSCP value.
- Last 2 bits of ToS are explicit congestion notification (ECN).
- Layer 2 QoS
- Ethernet
- Class of Service (CoS)
- On 802.1P frame
- 3-bit priority (PRI) field
- 000 – Routine – Best-effort
- 001 – Priority – Medium priority
- 010 – Immediate – High priority
- 011 – Flash – Call signaling
- 100 – Flash-Override – Video conferencing
- 101 – Critical – Voice bearer
- 110 – Internet – Reserved
- 111 – Network – Reserved
- Frame Relay
- 1-bit discard eligible (DE) field
- ATM
- 1-bit cell loss priority (CLP) field
- MPLS (layer 2 1/2)
- 3-bit experimental (EXP) field
- By default, the 3 most significant ToS bits (IP Precedence bits) are copied to EXP
- Ethernet
- Per-hop Behavior (PHB)
- “an externally observable fowarding behavior of a network node toward a group of IP packets that have the same DSCP value”
- In other words, treat packets with the same DSCP value in the same manner – scheduling, queuing, policing, etc.
- Behavior aggregate (BA) is a group of packets with the same DSCP value
- DSCP
- DSCP is chopped up into 4 PHBs
- Class selector PHB – (000) old IP precedence compatibility
- Default PHB – (000) best effort
- Assured forwarding (AF) PHB – (001, 010, 011, 100) guarantee bandwidth
- Provides 4 queues for 4 classes of traffic (AF1-4)
- Also specifies drop preference (ex., AF41, A13) where second number is preference (higher is more probable to be dropped)
- Each queue must have (W)RED to avoid drops
- No queue is any better than the other
- Backward compatible with IP precedence
-
- Expedited forwarding (EF) PHB – (101) low delay
- Minimum delay
- Bandwidth guarantee
- Policing
- Expedited forwarding (EF) PHB – (101) low delay
- DSCP is chopped up into 4 PHBs
- Trust boundaries
- Establish DSCP values as close to the source as possible
- On the device (IP phone), access switch, or distribution switch
- The core should never assign DSCP values
- Only trust DSCP values from devices you trust
- Examine and rewrite values from untrust sources
- Establish DSCP values as close to the source as possible
- Network-based Application Recognition (NBAR)
- Protocol discovery – discovers what protocols you’re running on your network
- Traffic statistics collection – keeps tracks of stats on each protocol
- Traffic classification – NBAR protocols can be used in class-maps to define traffic to be services
- Packet description language models (PDLMs) – table of what protocols NBAR recognizes
- Limitations
- Doesn’t work on EtherChannel interfaces
- Only handles 24 URLs, hosts, or MIME types
- Only analyzes first 400 bytes of the packets
- Requires CEF
- Doesn’t work on HTTPS, multicasts, or fragments
- Ignored traffic destined for the router itself
- NBAR commands
- Router(config)# ip nbar pdlm pdlm-name : Update the PDLM table
- Router(config)# ip nbar port-map protocol-name [tcp|udp] port-number : Adds an entry to the PDLM table
- Router# show ip nbar port-map protocol-name : Shows what’s in the PDLM table
- Router# show ip nbar protocol-discovery : Shows what’s been discovered
- Router(config-cmap)# match protocol name : a class-map match for an NBAR-discovered protocol
- Special protocol matching
- Can match beyond the port number with deep packet inspection
- Matches HTTP hostname, URL, or MIME type
- Matches fast-track P2P
- Matches RTP content
ONT Notes – Intro to QoS
I’ll try to keep it a little shorter this time.
Major issues for converged enterprise networks
- Available bandwidth: competition among applications
- Fixes
- Increase bandwidth: More power!
- Properly queue based on classification and marking: QoS
- Compress: cRTP, TCP header compression, etc.
- Fixes
- Delay: Lead time to get a packet to the destination
- Types of delay
- Processing delay: routing, switch delay
- Queuing delay: how long a frame stays in an output queue
- Serialization delay: how long to put the frame on the wire
- Propagation delay: the time to cross the physical medium
- Types of delay
- Jitter (delay variation): Variation is the delay
- Different delays mean different arrival times
- De-jitter buffers save up packets to reduce jitter (like the old CD writers)
- Fixes
- More bandwidth
- Prioritize sensitive data and forward first
- Remark (reclassify) packets based on sensitivity
- Enable L2 payload compression: make sure compression delay isn’t worse than the jitter
- Use header compression
- Packet loss: Packets are lost in the network somewhere
- Fixes
- More bandwidth
- Increase buffers space: more room for the queue on the interface
- Provide guaranteed bandwidth: Queuing and QoS
- Congestion avoidance
- Random Early Detection (RED) and weighted RED (WRED) drop packets before the queue is full
- Selective dropping is better than FIFO or LIFO dropping
- Fixes
QoS History
- Priority queuing: gives certain data the right-of-way for transmission
- Weighted Fair Queuing (WFQ): prevents small packets from waiting too long for big packets
- RTP priority queuing: Gives voice packets the right-of-way
- CAC: Makes sure we don’t fill up the queue or pipe with voice traffic
Implementing QoS
- Step 1: Identify traffic types and requirements
- Network audit
- Business audit
- Define bandwidth requirements for each class found
- Step 2: Classify the traffic
- Common classes
- VOIP
- Mission-critical
- Signal traffic: for VOIP
- Transactional application: SAP, ERP
- Best-effort: Everything else
- Scavenger: Crap you don’t care about like P2P and your boss’s email
- Common classes
- Step 3: Define policies for each class
- Tasks for each class
- Set max bandwidth
- Set min bandwidth
- Assign relative priorities
- Apply congestion avoidance, congestion management, etc.
- Tasks for each class
QoS Models
- Best-effort: no QoS
- Scalable
- Easy
- No service guarantee: doesn’t care what you’re trying to do
- No service differentiation: all traffic is equal
- Integrated Service (IntServ)
- Hard-QoS
- Uses RSVP to guarantee bandwidth through the entire path
- Requires
- Admission control
- Classification
- Polices the traffic (ceiling)
- Queuing
- Scheduling
- Advantages
- End-to-end resource admission control
- Per-request policy admission control
- Signaling of dynamic ports
- Disadvantages
- Continuous signaling
- Not scalable
- Differentiated Services (DiffServ)
- Soft-QoS
- Configured on each hop
- Traffic is classified
- Enforces different treatment on different classes
- Defined based on business requirements
- Benefits
- Scalable
- Supports lots of service levels
- Drawbacks
- No absolute guarantee of service
- Complex configuration throughout network
QoS Implementation Methods
- CLI
- Old school
- Not used any more
- Modules QoS CLI (MQC)
- Step 1: class-map
- Step 2: policy-map
- Step 3: service-policy
- AutoQoS
- Automatically generates classes and policies based on traffic it sees
- Super-simple
- Requires CEF, NBAR, and correct bandwidth statements
- SDM QoS Wizard
- Next, next, next
- Can be used to implement, monitor, or troubleshoot QoS