Internetwork Expert s CCNP Bootcamp. Layer 2 Voice & Video Support. Power Over Ethernet. Required to centrally power small devices

Transcription

1 Internetwork Expert s CCNP Bootcamp Layer 2 Voice & Video Support Power Over Ethernet Required to centrally power small devices IP Phones Access Point Surveillance cameras PoE reduces Cabling requirements Centralized power management PoE compliant switches support power in Ethernet twisted pair Injectors could be used with other switches Copyright 2010 Internetwork Expert

2 Power Over Ethernet (cont.) Two incompatible detection methods Cisco Pre-Standard IEEE 802.1af Newer devices support both methods Automatic PoE requirement is detected Every switch has PoE budget Plan power usage in ahead Configuration Interface: power inline {auto never} Exec: show power inline Voice QoS Requirements VoIP traffic has strict QoS requirements In terms of Round Trip Time In terms of Jitter In terms of packet loss Packet networks are statistically multiplexed Oversubscription is possible Even over engineered network may have traffic bursts over capacity VoIP deployment requires QoS mechanics Copyright 2010 Internetwork Expert

3 DiffServ QoS Review Instead of dealing with traffic flows, introduces traffic classes E.g. differentiate voice vs. data Scales with large number of node Classification is performed at the edge of network Packet Marking preserves classification decision All devices must agree on common marking All devices should implement consistent QoS policy applied to classes DiffServ Classification Could be based on existing marking Layer 2 (Ethernet CoS) Layer 3 (IP Precedence & DSCP) Could be based on traffic characteristic Protocol, ports numbers (via access-lists) TCP/UDP ports Could be based on flow characteristics E.g. traffic is metered and exceeding packets are classified as low priority Copyright 2010 Internetwork Expert

4 DiffServ Marking Marking stores classification decision To be interpreted by receiving device Could be encoded differently Layer 2 CoS Layer 3 IP DSCP/IPP To maintain consistency, different layer markings should be in sync E.g. having CoS 5 with IPP of 0 is not illegal but makes little sense DiffServ Per-Hop Hop-Behavior (PHB) Actual policy implementation, based on marking Applies to traffic classes Could be of three general types Assured forwarding (reserves some bandwidth) Expedited forwarding (priority treatment) Best-Effort (no guarantees of any type) Implemented using Cisco s QoS tools Copyright 2010 Internetwork Expert

5 Trust Boundaries Accepting existing marking is called trusting Simplest classification method Saves configuration time and switch resources Relies on some other device to perform classification E.g. IP Phone marking VoIP traffic Trust boundary typically occurs on network edge Untrusted ports by default have their marking reset to zero Trust Boundary Examples Copyright 2010 Internetwork Expert

6 Configuring Trust Boundaries Trust state is configured per-port with the mls qos trust command Trust can be defined based on CoS IP Precedence DSCP Conditional Trust Based on CDP signaling (cisco-phone) For ports connected to IP phones, separate extension trust can be defined with switchport priority extend [cos trust] Voice VLANs Voice and Data traffic should be separated Different Transport Requirements Different Security Requirements Same VLAN could be used but normally not recommended Voice VLAN AKA Auxiliary VLAN Automatically Signaled to IP Phone via CDP Configured using switchport voice vlan Copyright 2010 Internetwork Expert

7 Voice VLANs (cont.) A single physical link can connect to a phone and PC at the same time Voice & data traffic must have some way of being differentiated 802.1Q trunk encapsulation typically used for this separation Also allows encoding of CoS value Regular Ethernet header has no CoS field Voice VLAN Variations SW1# interface FastEthernet0/1 switchport access vlan 20 switchport voice vlan 10! interface FastEthernet0/2 switchport access vlan 20 switchport voice vlan dot1p! interface FastEthernet0/3 switchport access vlan 20 switchport voice vlan untagged! interface FastEthernet0/4 switchport access vlan 20 switchport voice vlan none Copyright 2010 Internetwork Expert

8 Layer 2 AutoQoS Layer 2 AutoQoS simplifies QoS implementation for VoIP Effectively a macro that defines Trust boundaries Marking policy Classification policy Queueing policy Configured as port-level auto qos voip [cisco-phone cisco-softphone trust] Q&A Copyright 2010 Internetwork Expert