本文全稱應該是:Frame Relay Voice-Adaptive Traffic Shaping and Fragmentation,標題限制字數,沒辦法了
幀中繼的流量整型向來是個頭疼的地方,因爲本身QOS就已經夠亂,所以專門在這兒整理一下
QOS分爲以下幾類:
classification 包分類,包標記(based on prec or dscp in ip packets' tos)
congestion management 隊列(CQ/PQ/WFQ/CBWFQ/PQCBWFQ..)
congestion avoidance 隨機早期檢測(RANDOM DETECT)
policing and shaping 策略丟棄或流量整型,也稱爲congestion control
signalling RSVP
link efficiency mechanisms 壓縮及多鏈路捆綁等
概念上易混的是congestion management 和 congestion control / policing and shaping
下面是本文的重點:幀中繼語音自適應流量整型及分片
幀中繼上的流量整型分傳統方法(map-class)與MQC兩種
傳統方法只能做分片(語音包分片後獲得更高效率),對不同類型數據無法給足夠清晰的優先級,比如語音數據到達接口後,並不能優先於其它數據通過,只能在鏈路出現擁塞後,依據對端發來的BECN,將數據降速至MINCIR發送,從而給語音留出空餘帶寬,但此前的語音包肯定會受影響。
下面我們舉例說明MQC在這裏的應用及其優勢:
int s0/0
en fram
frame-relay fragmentation voice-adaptive deactivation 50
frame-relay interface-dlci 100
class Jackson //調用map-class
frame-relay fragment 80 end-to-end //fragment is here
map-class frame-relay Jackson //map-class在這兒只是個殼,主要是下面MQC
service-policy output cracker
class-map voice
match access-g 102
class-map data
match access-g 101
policy-map QQ
class voice
priority 10 //高優先級隊列
class data
bandwidth 10 //普通隊列,基本帶寬
policy-map cracker
class class-default
shape average 64000 //CIR
shape adaptive 32000 //MINCIR
shape fr-voice-adapt deactivation 50 //失效時間,如無語音通過,返回正常CIR速率
service-policy QQ
注意上文中MQC的應用,套了幾層而已,仔細區別一下就好